Sodium Reactor Experiment
Encyclopedia
The Sodium Reactor Experiment was a pioneering nuclear power
plant built by Atomics International
at the Santa Susana Field Laboratory
, nearby Simi Valley
, California. The reactor operated from 1957 to 1964. On July 12, 1957 the Sodium Reactor Experiment became the first nuclear reactor in the United States to produce electrical power for a commercial power grid by powering the nearby city of Moorpark. In July 1959, the reactor suffered a serious incident in which the reactor core was damaged causing the controlled release of radioactive gas to the atmosphere. The reactor was repaired and restarted in September 1960. In February 1964, the Sodium Reactor Experiment was operated for the last time. Removal of the deactivated reactor was completed in 1981. Recent competing technical analysis of the 1959 incident has produced contrasting conclusions regarding the types and quantities of radioactive materials released. Members of the neighboring communities have expressed concerns about the possible impacts to health and environment from the incident. In August 2009, the Department of Energy hosted a community workshop to discuss the 1959 incident.
, roughly thirty miles (forty km) northwest from downtown Los Angeles
in Simi Valley. During the time the Sodium Reactor Experiment was active, the Santa Susana Field Laboratory was operated by two separate business divisions of the North American Aviation
company. The Rocketdyne
division conducted liquid rocket engine testing and development at the site while the Atomics International division focused on the development of commercial nuclear reactors and the development of compact nuclear reactors for space applications.
installed and operated a 6.5 MW electric power generating system. Initial criticality
, (i.e. controlled nuclear fission) began on April 25, 1957.
The Los Angeles Times published a front page story when Moorpark was supplied with nuclear-generated electricity. Edward R Murrow’s See It Now
television show featured the event as a special news report broadcast on November 24, 1957. In July, 1958, Atomics International produced a movie explaining the construction of the Sodium Reactor Experiment facility.
The Sodium Reactor Experiment used sodium
as a coolant so heat generated in the reactor was transported by liquid sodium through the reactor facility piping system. The pumps used to move the sodium were hot oil centrifugal pump
s modified for use in a sodium system. A support system used an oil-like fluid called tetralin
to cool the pump seals which prevented leakage of the hot sodium at the pump shaft. In July 1959, tetralin seeped into the primary coolant system through a pump seal. The tetralin was decomposed by the high temperature sodium. The decomposed tetralin clogged several of the narrow cooling channels used by the sodium to remove heat from the reactor fuel elements. As the tetralin residues clogged the reactors internal cooling channels, 13 of the reactor's 43 fuel elements suffered overheating and were damaged. The exact date of the fuel damage is unknown but believed to be within the period of July 12 to July 26, 1959.
At the time, the operators were experiencing unusual reactor behavior but were unaware of the damage. They continued operations for several days before shutting down the reactor for examination. When the operators attempted to remove the fuel elements from the reactor, most were removed normally but some were found to be stuck. Pieces of the damaged fuel elements also fell to the bottom of the reactor. In the following months, Atomics International personnel removed all of the stuck fuel elements, retrieved the pieces of dropped fuel elements, cleaned the sodium system and installed a new reactor core. The Sodium Reactor Experiment was restarted on September 7, 1960 some fourteen months after the accident. In 1961, Atomics International produced a movie explaining the accident and how the recovery operation was conducted. The Sodium Reactor Experiment operated until February 15, 1964 without a similar incident.
In 1964 several modifications were made to the Sodium Reactor Experiment. These modifications were completed in May 1965 but the Atomic Energy Agency and Atomics International decided to close the reactor rather than restart it. Facility nuclear decommissioning
began in 1976 with the removal of the reactor core, support systems and radioactively contaminated soil beneath the building structure. The source of the contaminated soils underneath the building does not appear related to the 1959 reactor incident. Nuclear decommissioning was completed in 1981. In 1982, Atomics International produced a motion picture presentation about the decommissioning and decontamination of the Sodium Reactor Experiment.
A group of Health Physicists from the Argonne National Laboratory
performed independent sampling to determine if the then-current minimum cleanup standards for radioactive residuals were met. In 1985, the United States Department of Energy
completed their evaluation of the survey reports and certified “…that there is no evidence the facilities pose a radiological threat to either personnel or the environment.” In 1999, the remaining structures were torn down and removed from the site.
The purpose of the Sodium Reactor Experiment was to generally demonstrate the feasibility of a sodium-cooled reactor as a heat source for a commercial power reactor to produce electricity. A secondary objective was to obtain operational data on slightly enriched fuel and uranium thorium fuel mixtures. Accordingly, the reactor was designed as a flexible development facility and was considered a development tool with emphasis on investigation of fuel materials.
Compared to water (or steam), sodium has a relatively low vapor pressure
at the operating temperatures of the Sodium Reactor Experiment. High temperature water or steam operates at a much higher pressure than sodium does. The Sodium Reactor Experiment design utilized sodium as a coolant so that high pressure water systems would not be required. The reactor did not have a containment pressure vessel because the maximum credible accident would not release enough gas volume to require pressure containment. It was designed, however, to retain gases at about atmospheric pressure, and to reduce diffusion leakage from potentially contaminated gas.
The Sodium Reactor Experiment included a complex of buildings, work shops and support systems. The Sodium Reactor Experiment reactor was housed in the main reactor building which consisted of a high bay area and a hot cell
facility. Three cleaning cells were located within the main building. The cleaning cells were designed to wash sodium from the fuel elements with water under an inert atmosphere. The cleaning accommodated the examination of the fuel rods after the rods were removed from the reactor. Because sodium reacts violently with water, the wash cell was sealed off and flooded with inert gas to minimize the reaction during washing. Operators worked behind thick walls to limit their exposure to radiation emitted from the fuel elements which were loaded into the cell through a ceiling entrance hole normally covered with a heavy “shield plug.”
The reactor core sat in a lower portion of a vessel lined with stainless steel and filled with liquid sodium. The Sodium Reactor Experiment reactor core contained forty–three fuel elements each comprising seven fuel rods. A fuel rod was a stainless steel tube six feet long and filled with twelve uranium fuel slugs. Many of the fuel elements in the SRE were instrumented with thermocouples located in the center of the fuel materials at various positions in the core. Two of the thermocouples were monitored in the reactor control room while the remaining measurements were recorded on instrumentation outside of the control room
. The sodium temperature was also monitored at various points within the reactor system.
At full power, sodium at temperature of approximately 500 °F (260 °C) passed through the plenum area beneath the reactor core through the heat channels absorbing the heat released from the fuel elements and discharged into the upper pool about six feet deep above the core at an average temperature of 950 °F (510 °C). This space was filled with helium gas maintained at a pressure of approximately three pounds per square inch. Piping circulated 50,000 pounds (22,680 kg) of heated liquid sodium from the reactor vessel to either of two available heat exchangers. One heat exchanger transferred the heat from the primary sodium loop which in turn dissipated the heat in a steam generator that boiled water to make steam for use in a turbine/generator that produced electricity.
The gases used as a cover gas in the sodium systems, such as the reactor and fuel assembly wash cells, are potentially radioactive. The design of the Sodium Reactor Experiment support facilities was to collect all such gases into a tank, compress them, and put them into a gas hold up tank until they had decayed sufficiently to allow discharge into the environment from an outdoor stack.
to remove volatile contamination.
On July 13, the reactor experienced a series of temperature and radiation fluctuations, each called an ‘excursion’ because the events were an unexpected departure from the expected conditions. The power level rose from about 4 MW to about 14 MW, or 70 percent of full power over a period of roughly two minutes. The excursion required the operators to manually override a malfunctioning automatic control switch and the reactor was shut down. The switch was repaired and the reactor was slowly restarted. On the following day, monitors again indicated elevated airborne radiation levels within the reactor building. The source was identified at two specific locations at the reactor core loading face which are sealed and airborne radiation within the reactor building was reduced. The reactor was restarted but soon the operators saw some unusual behavior over the following few days: The reactor increased power faster than expected and the temperature difference between the reactor bottom (where the sodium enters) and the reactor top (where the sodium exits) was unusually high. Radioactivity within the reactor also unexpectedly increased. The operators performed a number of investigations and exercises to understand and correct the reactor behavior.
On July 23, it was decided to shut the reactor down because of high fuel temperatures and because the top/bottom reactor temperature differences did not improve. While moving the elements in an attempt to dislodge foreign material and hence lower the exit temperatures, it was noticed that four reactor elements were stuck. On July 26 the reactor was shut down and the first damaged fuel element was observed. There were no reported fatalities at the time of the incident.
On July 29, 1959, an ad-hoc Investigation Committee was formally established to study the incident and to make recommendations. On August 21, 1959, the Los Angeles Daily News
printed a story titled “Parted Fuel Element seen at Atomics International.” The article notes that “…a parted fuel element was observed” and “The fuel element damage is not an indication of unsafe reactor conditions. No release of radioactive materials to the plant or its environs occurred.” The Investigation Committee released “SRE Fuel Element Damage, An Interim Report” on November 15, 1959. The Final Report is dated 1961. The front matter for both documents contain the following statement ”This report has been distributed according to the category ‘Reactors-Power’ as given in Standard Distribution Lists for Unclassified Scientific and Technical Reports.” The statement also notes that a total of 700 copies were printed. The document was not labeled “secret.”
Following the incident, Atomics International personnel documented an analysis of the distribution of radioactive materials released into the reactor by the damaged fuel elements. The analysis reviewed the radioactive materials released into the sodium and cover gas above the reactor. The researchers determined the amount of radioactive materials released into the sodium and noted the materials were successfully removed by using cold traps and that the sodium was reused when the reactor returned to service. The document states that only radioactive xenon-133 and krypton-85
were found in the cover gas. Attempts to detect radioactive iodine-131
were unsuccessful and could not be explained by Atomics International at the time. Internal Atomics International memoranda show the gases were removed from the reactor following the incident and stored in tanks where they were allowed to decay then slowly released to the atmosphere (see memoranda presented in Daniel Appendix C and F.)
A summary of the radioactive gases released from the Sodium Reactor Experiment over a two month period was prepared by The Boeing Company. The document summarizes the internal company memoranda that recorded the release of radioactive gases before, during and after the July 1959 incident. The document notes that 28 curies of fission gases was released to the environment through a stack in a controlled manner that met Federal requirements.
. The Three Mile Island accident
sparked interest by students and faculty member Daniel Hirsch at University of California Los Angeles who acquired the extensive collection of documentation and film footage of the damaged reactor. The documents and film was supplied to the local media, triggering extensive coverage.
In December 2003, the United States Environmental Protection Agency
(EPA) completed an evaluation of the portion of Santa Susana Field Laboratory previously involved with nuclear reactor development, including the Sodium Reactor Experiment site. The evaluation was based on data including any remaining radiological impacts to water and soils in the area of the Sodium Reactor Experiment. The EPA determined “the site is not eligible for inclusion on Superfund
’s National Priorities List
and no further Superfund response is warranted at this time.”
In February 2004, a class action
lawsuit was filed against the current landowner, The Boeing Company, alleging (in part) the Sodium Reactor Experiment caused harm to nearby residents. The plaintiffs produced an analysis of the incident prepared by expert witness
Arjun Makhijani
, PhD. The analysis of the Sodium Reactor Experiment by Dr. Makhijani reportedly estimates the incident at the Sodium Reactor Experiment may have released up to 260 times more radioactive iodine-131
than the official estimates for the Three Mile Island Nuclear Generating Station
release. The ‘260 times worse than Three Mile Island” has been widely quoted. The 'Three Mile Island' conclusion presented in the legal filing did not agree with data and documents prepared at the time of the SRE incident.
In August 2004, groundwater underneath the former Sodium Reactor Experiment was sampled to determine the presence of the radioactive material tritium
. Tritium was not detected. The results were presented at a DOE –sponsored public community meetings in June 2005 and in hand outs provided during the June 2005 community meeting.
In May 2005, a response to the Makhijani analysis was prepared for the defense
by Jerry Christian, PhD who provided a technical analysis disputing Makhijani’s claim of iodine release following the incident. Christian noted Atomics International personnel attempted to monitor iodine-131 without success and reactor temperature conditions did not allow the significant formation of iodine. Another, more detailed analysis was prepared for the plaintiffs by John A Daniel. Daniel focused on evaluating the plant conditions, radiation monitoring and documentation to determine the amount of radioactivity released. The analysis by Daniel concluded that only a smaller amount of radioactive gases were released from the SRE. The technical analysis by Jerry Christian and John Daniel contrasted with the analysis prepared by Makhihjani. The case was settled, reportedly with a large payment by Boeing to the plaintiffs, residents nearby the Santa Susana Field Laboratory who allegedly had cancer and other injuries from historical site activities including the SRE incident.
In July 2006, the History Channel broadcast a video summary of the 1959 Sodium Reactor Experiment incident within episode 19 of the “Engineering Disasters” documentary series. The segment features quotes from Dan Hirsch, a nuclear policy analyst and David Lochbaum. The documentary alleges the incident was kept secret for twenty years and that the radiation release from the incident could be as high as 240 times the radiation released from the accident at the Three Mile Island Nuclear Generating Station. The Engineering Disasters segment did not mention the technical analysis prepared by Boeing.
In October 2006, California legislators, responding to community calls for independent health studies in the wake of revelations about the site, established the Santa Susana Field Laboratory Advisory Panel. It consisted of independent experts from around the country (and one from Britain) as well as community representatives. The panel was a project of the Tides Center
, and the effort was funded by the US Department of Energy, and later by the California Environmental Protection Agency
, as arranged by the California State Legislature. The panel released a set of documents presenting analysis of various events at the Santa Susana Field Laboratory
. Five reports by consultants focused on the analysis of the radiological impacts of the July 1959 Sodium Reactor Experiment incident. One analysis by David Lochbaum, a Nuclear Safety Engineer, concluded that contrary to Rocketdyne's claim that no radioactivity was released to the environment, "as much as 30% of the most worrisome of the radionuclides, iodine-131 and cesium-137, may have been released, with a best estimate of 15% of each." Scant and disconnected data prevented a quantitative assessment of exactly what got out when. In another report, Jan Beya, attempted to provide an exposure estimate to epidemiologists who are interested in deciding the effectiveness of studies of radiation induced disease around the Santa Susana Field Laboratory. Beya noted that some meteorological information was withheld by the plant owner (The Boeing Company), thus the estimates within the report were limited to scoping calculations carrying a wide range of uncertainty, but nevertheless represent the current state of knowledge about the accident and its consequences, as reflected in the opinion of experts who have analyzed the event.
In September 2008, Daniel Hirsch presented testimony to the U.S. Senate, before the Committee on Environment and Public Works, Chaired by California Senator Barbara Boxer
. Mr. Hirsch called the July, 1959 event “one of the worst nuclear accidents in nuclear history” and the government “covered up the seriousness of the accident.” A contrasting viewpoint based on the technical analysis prepared by Boeing was not presented at the hearing.
In April 2009, The Department of Energy announced the transfer of $38.3 million to the EPA to provide for a complete radiological survey of a 290 acres (1.2 km²) area of the Santa Susana Field Laboratory. The source of the funds was the American Recovery and Reinvestment Act of 2009
. The DOE had provided funds earlier to the EPA for a portion of the survey, so the total funding provided for the Area IV survey is $41.5 million. The survey is expected to be completed in September, 2011.
In July 2009, local media recognized the fifty year anniversary of the July, 1959 SRE incident. Local media reported a former employee named John Pace "broke his 50 year vow of secrecy" to describe his role in the reactor incident and recovery. A local newspaper featured photographs purportedly of Mr. Pace performing various activities at the SRE including using an instrument to monitor the reactor, helping to physically rotate the top of the reactor core, placing sealer on asbestos piping and seated at a console operating the nuclear reactor. The claims of secrecy contrast with the release of a press release, a motion picture and numerous reports to the general public following the 1959 incident.
Jan Beya was interviewed by a local newspaper and reaffirmed his assertion that iodine-131 was released during the SRE incident but that it wouldn't have produced a widespread effect on health.
In August 2009, the Department of Energy hosted a public workshop in Simi Valley
designed to explore the diverse expert and community perspectives on what occurred prior to, during, and immediately after the July 1959 incident. The workshop featured presentations from three independent experts: Dr. Paul Pickard of Sandia National Laboratories
, Dr. Thomas Cochran of the Natural Resources Defense Council
, and Dr. Richard Denning of Ohio State University
. Over 185 workshop attendees including community members and Atomics International
retirees who had an opportunity to interact with the experts. An electronic library of over 80 documents, articles, text book descriptions, and symposia proceedings describing the design, operations, causes of the accident, activities taken to recover and restart the reactor, and decommissioning of the reactor facility. Workshop posters presenting timelines for the SRE history and Run 14, details regarding the operation of the SRE and the accident], and radioactive production and decay of the SRE reactor inventory were displayed at the workshop with the featured experts available to answer queations. Video of the introductions, presentations, community comments and the question and answer session are available for viewing.
As a result of the incident, a number of changes were made to the Sodium Reactor Experiment. Tetralin was eliminated, the sodium system was modified, the wash cell cleaning process switched from water to steam, instrumentation was improved and the fuel element geometry was modified. In September 1960, following recovery and cleanup operations, the Sodium Reactor Experiment began operation with a new reactor core. At the time of the July 1959 incident, the Sodium Reactor Experiment had operated for 10,344 hours. After the repairs were made and a new core loaded, the Sodium Reactor Experiment operated for an additional 26,716 hours and generated a total of 37 GWh of electricity.
In 1966, the Energy Technology Engineering Center
was established at the Santa Susana Field Laboratory by the U.S. Atomic Energy Commission to provide development and non-nuclear testing of liquid metal reactor components. The testing and development notably improved the safety and reliability of sodium pump seals. The Energy Technology Engineering Center designed, developed and performed full-scale testing for a wide variety of sodium components such as cold traps, flow meters and valves from 1965 to 1998.
Nuclear power
Nuclear power is the use of sustained nuclear fission to generate heat and electricity. Nuclear power plants provide about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity...
plant built by Atomics International
Atomics International
Atomics International was a division of the North American Aviation company which engaged principally in the early development of nuclear technology and nuclear reactors for both commercial and government applications...
at the Santa Susana Field Laboratory
Santa Susana Field Laboratory
The Santa Susana Field Laboratory is a complex of industrial research and development facilities located on a 2,668 acre portion of the Southern California Simi Hills in Simi Valley, California, used mainly for the testing and development of Liquid-propellant rocket engines for the United States...
, nearby Simi Valley
Simi Valley, California
-2010:The 2010 United States Census reported that Simi Valley had a population of 124,237. The population density was 2,940.8 people per square mile...
, California. The reactor operated from 1957 to 1964. On July 12, 1957 the Sodium Reactor Experiment became the first nuclear reactor in the United States to produce electrical power for a commercial power grid by powering the nearby city of Moorpark. In July 1959, the reactor suffered a serious incident in which the reactor core was damaged causing the controlled release of radioactive gas to the atmosphere. The reactor was repaired and restarted in September 1960. In February 1964, the Sodium Reactor Experiment was operated for the last time. Removal of the deactivated reactor was completed in 1981. Recent competing technical analysis of the 1959 incident has produced contrasting conclusions regarding the types and quantities of radioactive materials released. Members of the neighboring communities have expressed concerns about the possible impacts to health and environment from the incident. In August 2009, the Department of Energy hosted a community workshop to discuss the 1959 incident.
Location and setting
The Sodium Reactor Experiment facility was situated within a northwestern administrative section (called “Area IV”) of the Santa Susana Field LaboratorySanta Susana Field Laboratory
The Santa Susana Field Laboratory is a complex of industrial research and development facilities located on a 2,668 acre portion of the Southern California Simi Hills in Simi Valley, California, used mainly for the testing and development of Liquid-propellant rocket engines for the United States...
, roughly thirty miles (forty km) northwest from downtown Los Angeles
Los Ángeles
Los Ángeles is the capital of the province of Biobío, in the commune of the same name, in Region VIII , in the center-south of Chile. It is located between the Laja and Biobío rivers. The population is 123,445 inhabitants...
in Simi Valley. During the time the Sodium Reactor Experiment was active, the Santa Susana Field Laboratory was operated by two separate business divisions of the North American Aviation
North American Aviation
North American Aviation was a major US aerospace manufacturer, responsible for a number of historic aircraft, including the T-6 Texan trainer, the P-51 Mustang fighter, the B-25 Mitchell bomber, the F-86 Sabre jet fighter, the X-15 rocket plane, and the XB-70, as well as Apollo Command and Service...
company. The Rocketdyne
Rocketdyne
Rocketdyne was a Rocket engine design and production company headquartered in Canoga Park, California, United States. The company was related to North American Aviation for most of its history. NAA merged with Rockwell International, which was then bought by Boeing in December, 1996...
division conducted liquid rocket engine testing and development at the site while the Atomics International division focused on the development of commercial nuclear reactors and the development of compact nuclear reactors for space applications.
History
In 1954, the United States Atomic Energy Commission announced plans to test the basic nuclear reactor designs then under study by building five experimental reactors within five years. The Sodium Reactor Experiment, designed by Atomics International, was one of the chosen reactors. Intensive design of the Sodium Reactor Experiment began in June 1954 with construction underway in April 1955. A local utility company, Southern California EdisonSouthern California Edison
Southern California Edison , the largest subsidiary of Edison International , is the primary electricity supply company for much of Southern California, USA. It provides 14 million people with electricity...
installed and operated a 6.5 MW electric power generating system. Initial criticality
Criticality
Criticality may refer to:* Critical thinking in education* Critical reflection in adult education* Critical mass in nuclear reactions* Criticality accident* Criticality matrix* Nuclear Criticality Safety...
, (i.e. controlled nuclear fission) began on April 25, 1957.
The Los Angeles Times published a front page story when Moorpark was supplied with nuclear-generated electricity. Edward R Murrow’s See It Now
See It Now
See It Now is an American newsmagazine and documentary series broadcast by CBS from 1951 to 1958. It was created by Edward R. Murrow and Fred W. Friendly, Murrow being the host of the show. From 1952 to 1957, See It Now won four Emmy Awards and was nominated three times...
television show featured the event as a special news report broadcast on November 24, 1957. In July, 1958, Atomics International produced a movie explaining the construction of the Sodium Reactor Experiment facility.
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
as a coolant so heat generated in the reactor was transported by liquid sodium through the reactor facility piping system. The pumps used to move the sodium were hot oil centrifugal pump
Centrifugal pump
A centrifugal pump is a rotodynamic pump that uses a rotating impeller to create flow by the addition of energy to a fluid. Centrifugal pumps are commonly used to move liquids through piping...
s modified for use in a sodium system. A support system used an oil-like fluid called tetralin
Tetralin
Tetralin is a hydrocarbon having the chemical formula C10H12. This molecule is similar to the naphthalene chemical structure except that one ring is saturated.The compound can be synthesized in a Bergman cyclization...
to cool the pump seals which prevented leakage of the hot sodium at the pump shaft. In July 1959, tetralin seeped into the primary coolant system through a pump seal. The tetralin was decomposed by the high temperature sodium. The decomposed tetralin clogged several of the narrow cooling channels used by the sodium to remove heat from the reactor fuel elements. As the tetralin residues clogged the reactors internal cooling channels, 13 of the reactor's 43 fuel elements suffered overheating and were damaged. The exact date of the fuel damage is unknown but believed to be within the period of July 12 to July 26, 1959.
At the time, the operators were experiencing unusual reactor behavior but were unaware of the damage. They continued operations for several days before shutting down the reactor for examination. When the operators attempted to remove the fuel elements from the reactor, most were removed normally but some were found to be stuck. Pieces of the damaged fuel elements also fell to the bottom of the reactor. In the following months, Atomics International personnel removed all of the stuck fuel elements, retrieved the pieces of dropped fuel elements, cleaned the sodium system and installed a new reactor core. The Sodium Reactor Experiment was restarted on September 7, 1960 some fourteen months after the accident. In 1961, Atomics International produced a movie explaining the accident and how the recovery operation was conducted. The Sodium Reactor Experiment operated until February 15, 1964 without a similar incident.
In 1964 several modifications were made to the Sodium Reactor Experiment. These modifications were completed in May 1965 but the Atomic Energy Agency and Atomics International decided to close the reactor rather than restart it. Facility nuclear decommissioning
Nuclear decommissioning
Nuclear decommissioning is the dismantling of a nuclear power plant and decontamination of the site to a state no longer requiring protection from radiation for the general public...
began in 1976 with the removal of the reactor core, support systems and radioactively contaminated soil beneath the building structure. The source of the contaminated soils underneath the building does not appear related to the 1959 reactor incident. Nuclear decommissioning was completed in 1981. In 1982, Atomics International produced a motion picture presentation about the decommissioning and decontamination of the Sodium Reactor Experiment.
A group of Health Physicists from the Argonne National Laboratory
Argonne National Laboratory
Argonne National Laboratory is the first science and engineering research national laboratory in the United States, receiving this designation on July 1, 1946. It is the largest national laboratory by size and scope in the Midwest...
performed independent sampling to determine if the then-current minimum cleanup standards for radioactive residuals were met. In 1985, the United States Department of Energy
United States Department of Energy
The United States Department of Energy is a Cabinet-level department of the United States government concerned with the United States' policies regarding energy and safety in handling nuclear material...
completed their evaluation of the survey reports and certified “…that there is no evidence the facilities pose a radiological threat to either personnel or the environment.” In 1999, the remaining structures were torn down and removed from the site.
Principles
Compared to water (or steam), sodium has a relatively low vapor pressure
Vapor pressure
Vapor pressure or equilibrium vapor pressure is the pressure of a vapor in thermodynamic equilibrium with its condensed phases in a closed system. All liquids have a tendency to evaporate, and some solids can sublimate into a gaseous form...
at the operating temperatures of the Sodium Reactor Experiment. High temperature water or steam operates at a much higher pressure than sodium does. The Sodium Reactor Experiment design utilized sodium as a coolant so that high pressure water systems would not be required. The reactor did not have a containment pressure vessel because the maximum credible accident would not release enough gas volume to require pressure containment. It was designed, however, to retain gases at about atmospheric pressure, and to reduce diffusion leakage from potentially contaminated gas.
The Sodium Reactor Experiment included a complex of buildings, work shops and support systems. The Sodium Reactor Experiment reactor was housed in the main reactor building which consisted of a high bay area and a hot cell
Hot cell
Shielded nuclear radiation containment chambers are commonly referred to as hot cells. The word "hot" refers to radioactivity.Hot cells are used in both the nuclear-energy and the nuclear-medicines industries....
facility. Three cleaning cells were located within the main building. The cleaning cells were designed to wash sodium from the fuel elements with water under an inert atmosphere. The cleaning accommodated the examination of the fuel rods after the rods were removed from the reactor. Because sodium reacts violently with water, the wash cell was sealed off and flooded with inert gas to minimize the reaction during washing. Operators worked behind thick walls to limit their exposure to radiation emitted from the fuel elements which were loaded into the cell through a ceiling entrance hole normally covered with a heavy “shield plug.”
Control room
A control room is a room serving as an operations centre where a facility or service can be monitored and controlled. Examples include:*in television production, the master control is the technical hub of a broadcast operation common among most over-the-air television stations, television networks...
. The sodium temperature was also monitored at various points within the reactor system.
At full power, sodium at temperature of approximately 500 °F (260 °C) passed through the plenum area beneath the reactor core through the heat channels absorbing the heat released from the fuel elements and discharged into the upper pool about six feet deep above the core at an average temperature of 950 °F (510 °C). This space was filled with helium gas maintained at a pressure of approximately three pounds per square inch. Piping circulated 50,000 pounds (22,680 kg) of heated liquid sodium from the reactor vessel to either of two available heat exchangers. One heat exchanger transferred the heat from the primary sodium loop which in turn dissipated the heat in a steam generator that boiled water to make steam for use in a turbine/generator that produced electricity.
The gases used as a cover gas in the sodium systems, such as the reactor and fuel assembly wash cells, are potentially radioactive. The design of the Sodium Reactor Experiment support facilities was to collect all such gases into a tank, compress them, and put them into a gas hold up tank until they had decayed sufficiently to allow discharge into the environment from an outdoor stack.
State of knowledge in 1959
The design and construction of the Sodium Reactor Experiment was to gain operating experience using uranium fuel in a reactor used to produce electricity. The fuel elements in the Sodium Reactor Experiment were operating under untried conditions. Fuel design limits were based on theoretical limits, not operating experience. Cladding materials were likewise untested, with little or no operating experience.Reactor operation before incident
During the operation of the Sodium Reactor Experiment the operators conducted a number of test cycles, called “runs,” intended to make corrections and modifications to the facility support systems, conduct reactor physics experiments and generate electricity. During run 3, the Sodium Reactor Experiment became the first nuclear reactor in the United States to produce power for a commercial power grid. During Run 8, a black residue (believed to be decomposed tetralin) was noticed on fuel elements removed from the reactor. The fuel elements were washed in the wash cell and returned to the reactor. The reactor returned to operation for high temperature reactor testing. Several anomalous temperature readings were occasionally noticed during the next few runs while the operators attempted to understand the behavior and its cause. At the end of run 13, it was obvious that something had occurred to impair the heat transfer characteristics of the system. It was decided that a tetralin leak had occurred again and was the cause of the trouble. The reactor sodium was purged with gaseous nitrogenNitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
to remove volatile contamination.
Wash Cell explosion
Following run 13, an attempt was made to wash a fuel element in the wash cell. During the operation, an explosion occurred of sufficient magnitude to lift the shield plug out of the wash cell. It is believed the tetralin-related decomposition products caused a substantial amount of sodium to be trapped within the fuel rod elements by blocking some drain holes. There were no reported injuries or fatalities associated with the wash cell explosion. As a result of the explosion, no further washing of the elements was done. Measurements taken from the inside of the Reactor Building, indicated extremely high radioactive material contamination levels within the entire building. Within several days the general high bay had been decontaminated and restored to normal contamination levels, except for the area immediately around the wash cells.Run 14 (July 12 to July 26, 1959)
Shortly after the reactor was restarted, radiation monitors inside the reactor building showed a sharp increase in airborne radioactivity within the reactor building. The reactor remained operating while attempts were made to determine where the radioactivity was coming from. Airborne radioactivity returned to normal conditions.On July 13, the reactor experienced a series of temperature and radiation fluctuations, each called an ‘excursion’ because the events were an unexpected departure from the expected conditions. The power level rose from about 4 MW to about 14 MW, or 70 percent of full power over a period of roughly two minutes. The excursion required the operators to manually override a malfunctioning automatic control switch and the reactor was shut down. The switch was repaired and the reactor was slowly restarted. On the following day, monitors again indicated elevated airborne radiation levels within the reactor building. The source was identified at two specific locations at the reactor core loading face which are sealed and airborne radiation within the reactor building was reduced. The reactor was restarted but soon the operators saw some unusual behavior over the following few days: The reactor increased power faster than expected and the temperature difference between the reactor bottom (where the sodium enters) and the reactor top (where the sodium exits) was unusually high. Radioactivity within the reactor also unexpectedly increased. The operators performed a number of investigations and exercises to understand and correct the reactor behavior.
On July 23, it was decided to shut the reactor down because of high fuel temperatures and because the top/bottom reactor temperature differences did not improve. While moving the elements in an attempt to dislodge foreign material and hence lower the exit temperatures, it was noticed that four reactor elements were stuck. On July 26 the reactor was shut down and the first damaged fuel element was observed. There were no reported fatalities at the time of the incident.
On July 29, 1959, an ad-hoc Investigation Committee was formally established to study the incident and to make recommendations. On August 21, 1959, the Los Angeles Daily News
Los Angeles Daily News
The Los Angeles Daily News is the second-largest circulating daily newspaper of Los Angeles, California. It is the flagship of the Los Angeles Newspaper Group, a branch of Colorado-based MediaNews Group....
printed a story titled “Parted Fuel Element seen at Atomics International.” The article notes that “…a parted fuel element was observed” and “The fuel element damage is not an indication of unsafe reactor conditions. No release of radioactive materials to the plant or its environs occurred.” The Investigation Committee released “SRE Fuel Element Damage, An Interim Report” on November 15, 1959. The Final Report is dated 1961. The front matter for both documents contain the following statement ”This report has been distributed according to the category ‘Reactors-Power’ as given in Standard Distribution Lists for Unclassified Scientific and Technical Reports.” The statement also notes that a total of 700 copies were printed. The document was not labeled “secret.”
Release of radioactive materials to the environment
The Sodium Reactor Experiment core, high bay, reactor gas and exhaust stack were routinely monitored using radiation detectors. Monitoring was underway at the time of the incident and substantial documents appear to be available (see Daniel, Appendix C and F) Two sets of documentation appear to exist concerning the release of radioactive gases from the 1959 incident. The first set of documents is represented by the various incident reports, technical analysis and radiation monitoring reports prepared by Atomics International personnel shortly after the incident. The second set of documents were primarily prepared to support or defend a lawsuit against the current property owner (The Boeing Company) some forty five years after the incident.Following the incident, Atomics International personnel documented an analysis of the distribution of radioactive materials released into the reactor by the damaged fuel elements. The analysis reviewed the radioactive materials released into the sodium and cover gas above the reactor. The researchers determined the amount of radioactive materials released into the sodium and noted the materials were successfully removed by using cold traps and that the sodium was reused when the reactor returned to service. The document states that only radioactive xenon-133 and krypton-85
Krypton-85
Krypton 85 is a radioisotope of krypton.It decays into rubidium-85, with a half-life of 10.756 years and a maximum decay energy of 0.687 MeV.Its most common decay is by beta particle emission with maximum energy of 687...
were found in the cover gas. Attempts to detect radioactive iodine-131
Iodine-131
Iodine-131 , also called radioiodine , is an important radioisotope of iodine. It has a radioactive decay half-life of about eight days. Its uses are mostly medical and pharmaceutical...
were unsuccessful and could not be explained by Atomics International at the time. Internal Atomics International memoranda show the gases were removed from the reactor following the incident and stored in tanks where they were allowed to decay then slowly released to the atmosphere (see memoranda presented in Daniel Appendix C and F.)
A summary of the radioactive gases released from the Sodium Reactor Experiment over a two month period was prepared by The Boeing Company. The document summarizes the internal company memoranda that recorded the release of radioactive gases before, during and after the July 1959 incident. The document notes that 28 curies of fission gases was released to the environment through a stack in a controlled manner that met Federal requirements.
Controversy
In recent times, the July 1959 incident at the Sodium Reactor Experiment was first referenced in a 1976 report on various nuclear activities in Los Angeles in a little-noticed publication by Another Mother For PeaceAnother Mother For Peace
Another Mother for Peace is a grass-roots anti-war advocacy group founded in 1967 in opposition to the U.S. war in Vietnam. The association is “dedicated to eliminating the use of war as a means of solving disputes among nations, people and ideologies...
. The Three Mile Island accident
Three Mile Island accident
The Three Mile Island accident was a core meltdown in Unit 2 of the Three Mile Island Nuclear Generating Station in Dauphin County, Pennsylvania near Harrisburg, United States in 1979....
sparked interest by students and faculty member Daniel Hirsch at University of California Los Angeles who acquired the extensive collection of documentation and film footage of the damaged reactor. The documents and film was supplied to the local media, triggering extensive coverage.
In December 2003, the United States Environmental Protection Agency
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...
(EPA) completed an evaluation of the portion of Santa Susana Field Laboratory previously involved with nuclear reactor development, including the Sodium Reactor Experiment site. The evaluation was based on data including any remaining radiological impacts to water and soils in the area of the Sodium Reactor Experiment. The EPA determined “the site is not eligible for inclusion on Superfund
Superfund
Superfund is the common name for the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 , a United States federal law designed to clean up sites contaminated with hazardous substances...
’s National Priorities List
National Priorities List
The National Priorities List is the list of hazardous waste sites in the United States eligible for long-term remedial action financed under the federal Superfund program. Environmental Protection Agency regulations outline a formal process for assessing hazardous waste sites and placing them on...
and no further Superfund response is warranted at this time.”
In February 2004, a class action
Class action
In law, a class action, a class suit, or a representative action is a form of lawsuit in which a large group of people collectively bring a claim to court and/or in which a class of defendants is being sued...
lawsuit was filed against the current landowner, The Boeing Company, alleging (in part) the Sodium Reactor Experiment caused harm to nearby residents. The plaintiffs produced an analysis of the incident prepared by expert witness
Expert witness
An expert witness, professional witness or judicial expert is a witness, who by virtue of education, training, skill, or experience, is believed to have expertise and specialised knowledge in a particular subject beyond that of the average person, sufficient that others may officially and legally...
Arjun Makhijani
Arjun Makhijani
Arjun Makhijani is an electrical and nuclear engineer who is President of the Institute for Energy and Environmental Research. Makhijani has written many books and reports analyzing the safety, economics, and efficiency of various energy sources...
, PhD. The analysis of the Sodium Reactor Experiment by Dr. Makhijani reportedly estimates the incident at the Sodium Reactor Experiment may have released up to 260 times more radioactive iodine-131
Iodine-131
Iodine-131 , also called radioiodine , is an important radioisotope of iodine. It has a radioactive decay half-life of about eight days. Its uses are mostly medical and pharmaceutical...
than the official estimates for the Three Mile Island Nuclear Generating Station
Three Mile Island Nuclear Generating Station
Three Mile Island Nuclear Generating Station is a civilian nuclear power plant located on Three Mile Island in the Susquehanna River, south of Harrisburg, Pennsylvania. It has two separate units, known as TMI-1 and TMI-2...
release. The ‘260 times worse than Three Mile Island” has been widely quoted. The 'Three Mile Island' conclusion presented in the legal filing did not agree with data and documents prepared at the time of the SRE incident.
In August 2004, groundwater underneath the former Sodium Reactor Experiment was sampled to determine the presence of the radioactive material tritium
Tritium
Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...
. Tritium was not detected. The results were presented at a DOE –sponsored public community meetings in June 2005 and in hand outs provided during the June 2005 community meeting.
In May 2005, a response to the Makhijani analysis was prepared for the defense
Defense (legal)
In civil proceedings and criminal prosecutions under the common law, a defendant may raise a defense in an attempt to avoid criminal or civil liability...
by Jerry Christian, PhD who provided a technical analysis disputing Makhijani’s claim of iodine release following the incident. Christian noted Atomics International personnel attempted to monitor iodine-131 without success and reactor temperature conditions did not allow the significant formation of iodine. Another, more detailed analysis was prepared for the plaintiffs by John A Daniel. Daniel focused on evaluating the plant conditions, radiation monitoring and documentation to determine the amount of radioactivity released. The analysis by Daniel concluded that only a smaller amount of radioactive gases were released from the SRE. The technical analysis by Jerry Christian and John Daniel contrasted with the analysis prepared by Makhihjani. The case was settled, reportedly with a large payment by Boeing to the plaintiffs, residents nearby the Santa Susana Field Laboratory who allegedly had cancer and other injuries from historical site activities including the SRE incident.
In July 2006, the History Channel broadcast a video summary of the 1959 Sodium Reactor Experiment incident within episode 19 of the “Engineering Disasters” documentary series. The segment features quotes from Dan Hirsch, a nuclear policy analyst and David Lochbaum. The documentary alleges the incident was kept secret for twenty years and that the radiation release from the incident could be as high as 240 times the radiation released from the accident at the Three Mile Island Nuclear Generating Station. The Engineering Disasters segment did not mention the technical analysis prepared by Boeing.
In October 2006, California legislators, responding to community calls for independent health studies in the wake of revelations about the site, established the Santa Susana Field Laboratory Advisory Panel. It consisted of independent experts from around the country (and one from Britain) as well as community representatives. The panel was a project of the Tides Center
Tides Center
Tides Center is a non-profit organization in the United States which provides fiscal sponsorship for progressive groups. Tides Center is classified a 501 tax-exempt organization by the IRS...
, and the effort was funded by the US Department of Energy, and later by the California Environmental Protection Agency
California Environmental Protection Agency
The California Environmental Protection Agency is a state cabinet-level agency within the government of California. Cal/EPA is composed of six departments, boards and offices responsible for environmental research, regulating and administering the state's environmental protection programs, and...
, as arranged by the California State Legislature. The panel released a set of documents presenting analysis of various events at the Santa Susana Field Laboratory
Santa Susana Field Laboratory
The Santa Susana Field Laboratory is a complex of industrial research and development facilities located on a 2,668 acre portion of the Southern California Simi Hills in Simi Valley, California, used mainly for the testing and development of Liquid-propellant rocket engines for the United States...
. Five reports by consultants focused on the analysis of the radiological impacts of the July 1959 Sodium Reactor Experiment incident. One analysis by David Lochbaum, a Nuclear Safety Engineer, concluded that contrary to Rocketdyne's claim that no radioactivity was released to the environment, "as much as 30% of the most worrisome of the radionuclides, iodine-131 and cesium-137, may have been released, with a best estimate of 15% of each." Scant and disconnected data prevented a quantitative assessment of exactly what got out when. In another report, Jan Beya, attempted to provide an exposure estimate to epidemiologists who are interested in deciding the effectiveness of studies of radiation induced disease around the Santa Susana Field Laboratory. Beya noted that some meteorological information was withheld by the plant owner (The Boeing Company), thus the estimates within the report were limited to scoping calculations carrying a wide range of uncertainty, but nevertheless represent the current state of knowledge about the accident and its consequences, as reflected in the opinion of experts who have analyzed the event.
In September 2008, Daniel Hirsch presented testimony to the U.S. Senate, before the Committee on Environment and Public Works, Chaired by California Senator Barbara Boxer
Barbara Boxer
Barbara Levy Boxer is the junior United States Senator from California . A member of the Democratic Party, she previously served in the U.S. House of Representatives ....
. Mr. Hirsch called the July, 1959 event “one of the worst nuclear accidents in nuclear history” and the government “covered up the seriousness of the accident.” A contrasting viewpoint based on the technical analysis prepared by Boeing was not presented at the hearing.
In April 2009, The Department of Energy announced the transfer of $38.3 million to the EPA to provide for a complete radiological survey of a 290 acres (1.2 km²) area of the Santa Susana Field Laboratory. The source of the funds was the American Recovery and Reinvestment Act of 2009
American Recovery and Reinvestment Act of 2009
The American Recovery and Reinvestment Act of 2009, abbreviated ARRA and commonly referred to as the Stimulus or The Recovery Act, is an economic stimulus package enacted by the 111th United States Congress in February 2009 and signed into law on February 17, 2009, by President Barack Obama.To...
. The DOE had provided funds earlier to the EPA for a portion of the survey, so the total funding provided for the Area IV survey is $41.5 million. The survey is expected to be completed in September, 2011.
In July 2009, local media recognized the fifty year anniversary of the July, 1959 SRE incident. Local media reported a former employee named John Pace "broke his 50 year vow of secrecy" to describe his role in the reactor incident and recovery. A local newspaper featured photographs purportedly of Mr. Pace performing various activities at the SRE including using an instrument to monitor the reactor, helping to physically rotate the top of the reactor core, placing sealer on asbestos piping and seated at a console operating the nuclear reactor. The claims of secrecy contrast with the release of a press release, a motion picture and numerous reports to the general public following the 1959 incident.
Jan Beya was interviewed by a local newspaper and reaffirmed his assertion that iodine-131 was released during the SRE incident but that it wouldn't have produced a widespread effect on health.
In August 2009, the Department of Energy hosted a public workshop in Simi Valley
Simi Valley
Simi Valley is a synclinal valley in Southern California in the United States. It is an enclosed or hidden valley surrounded by mountains and hills. It is connected to the San Fernando Valley to the east by the Santa Susana Pass & 118 freeway, and in the west the narrows of the Arroyo Simi and 118...
designed to explore the diverse expert and community perspectives on what occurred prior to, during, and immediately after the July 1959 incident. The workshop featured presentations from three independent experts: Dr. Paul Pickard of Sandia National Laboratories
Sandia National Laboratories
The Sandia National Laboratories, managed and operated by the Sandia Corporation , are two major United States Department of Energy research and development national laboratories....
, Dr. Thomas Cochran of the Natural Resources Defense Council
Natural Resources Defense Council
The Natural Resources Defense Council is a New York City-based, non-profit, non-partisan international environmental advocacy group, with offices in Washington DC, San Francisco, Los Angeles, Chicago, and Beijing...
, and Dr. Richard Denning of Ohio State University
Ohio State University
The Ohio State University, commonly referred to as Ohio State, is a public research university located in Columbus, Ohio. It was originally founded in 1870 as a land-grant university and is currently the third largest university campus in the United States...
. Over 185 workshop attendees including community members and Atomics International
Atomics International
Atomics International was a division of the North American Aviation company which engaged principally in the early development of nuclear technology and nuclear reactors for both commercial and government applications...
retirees who had an opportunity to interact with the experts. An electronic library of over 80 documents, articles, text book descriptions, and symposia proceedings describing the design, operations, causes of the accident, activities taken to recover and restart the reactor, and decommissioning of the reactor facility. Workshop posters presenting timelines for the SRE history and Run 14, details regarding the operation of the SRE and the accident], and radioactive production and decay of the SRE reactor inventory were displayed at the workshop with the featured experts available to answer queations. Video of the introductions, presentations, community comments and the question and answer session are available for viewing.
Legacy
In 1966, the Energy Technology Engineering Center
Energy Technology Engineering Center
The Energy Technology Engineering Center , was a government-owned, contractor-operated complex of industrial facilities located within the Santa Susana Field Laboratory , Ventura County, California. The ETEC specialized in non-nuclear testing of components which were designed to transfer heat...
was established at the Santa Susana Field Laboratory by the U.S. Atomic Energy Commission to provide development and non-nuclear testing of liquid metal reactor components. The testing and development notably improved the safety and reliability of sodium pump seals. The Energy Technology Engineering Center designed, developed and performed full-scale testing for a wide variety of sodium components such as cold traps, flow meters and valves from 1965 to 1998.
Company websites
- U.S. DOE ETEC Closure Project Website
- Santa Susana Field Laboratory website Hosted by the Boeing Company
Sodium Reactor Experiment video
- Sodium Reactor Experiment Construction, July 1958
- Description of the July 1959 incident and recovery, November, 1961
- Removal of the Sodium Reactor Experiment, March 1982