Reactor grade plutonium nuclear test
Encyclopedia
Reactor-grade plutonium
is found in spent nuclear fuel
that a nuclear reactor
has irradiated (burnup
) for years instead of weeks or months, leading to transmutation
of much of the fissile
, relatively long half-life
isotope 239Pu
into other isotopes of plutonium
that are less fissile or more radioactive.
Thermal-neutron reactors (today's nuclear power plant
s) can reuse reactor-grade plutonium only to a limited degree as MOX fuel
, and only for a second cycle; fast-neutron reactors, which are uncommon today, can use this or any other actinide
material indefinitely.
The degree to which reactor-grade plutonium is less useful than weapons-grade plutonium for building nuclear weapon
s is debated, with many sources saying it is difficult or impossible, and others saying it is relatively easy with modern technologies like fusion boosting to overcome predetonation, remote manipulation for assembly of highly radioactive components, and cooling of the pit during storage to offset accumulation of decay heat
.
The difference is important in assessing significance in the context of nuclear proliferation
.
Reprocessing
of LWR (PWR
or BWR) spent fuel recovers reactor grade plutonium (as defined since 1976), not fuel grade.
The DOE
definition of reactor grade plutonium
changed in 1976. Up until 1976, two grades were recognised:
Weapons grade, less than 7% Pu-240
and
Reactor grade, 7% or more Pu-240.
From 1976, three grades were recognised:
Weapons grade, less than 7% Pu-240,
Fuel grade, 7% to 19% Pu-240 and
Reactor grade, more than 19% Pu-240.
nuclear test using non-weapons-grade
plutonium
, conducted at the US Nevada Test Site
in 1962. Some information regarding this test was declassified in July 1977 under instructions from President Jimmy Carter
as background to his decision to prohibit nuclear reprocessing
in the USA.
The plutonium used was manufactured in a Magnox reactor in the United Kingdom, and provided to the US under the 1958 US-UK Mutual Defence Agreement
. Its isotopic composition has not been disclosed, other than the description reactor grade and it has not been disclosed which definition was used in describing the material for this test as reactor grade. The plutonium was apparently sourced from the military Magnox reactors at Calder Hall or Chapelcross. The content of plutonium-239
in material used for the 1962 test is estimated to have been at least 85%, much higher than typical spent fuel from currently operating reactors.
s can use plutonium of any isotopic composition.
Reprocessing was planned in the 1960s when planners expected the uranium market
to become tight and fast breeder reactors to be needed to efficiently use uranium supplies. This became less urgent with reduced demand forecasts and increased uranium supplies, and commercial deployment of fast reactors was postponed.
Today's thermal reactor
s can reuse plutonium to a limited degree as MOX fuel
. Some reactors limit MOX fuel to a fraction of the total fuel load for nuclear stability reasons. Only the odd-mass isotopes of plutonium
are fissile
with thermal neutrons, and the even-mass isotopes accumulate. Plutonium-240
is a fertile material
like uranium-238
, becoming plutonium-241
on neutron capture, but plutonium-242
both has a low neutron capture
cross section
, and would require 3 neutron capture
s before becoming a fissile nuclide.
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...
is found in spent nuclear fuel
Spent nuclear fuel
Spent nuclear fuel, occasionally called used nuclear fuel, is nuclear fuel that has been irradiated in a nuclear reactor...
that a nuclear reactor
Nuclear reactor
A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...
has irradiated (burnup
Burnup
In nuclear power technology, burnup is a measure of how much energy is extracted from a primary nuclear fuel source...
) for years instead of weeks or months, leading to transmutation
Nuclear transmutation
Nuclear transmutation is the conversion of one chemical element or isotope into another. In other words, atoms of one element can be changed into atoms of other element by 'transmutation'...
of much of the fissile
Fissile
In nuclear engineering, a fissile material is one that is capable of sustaining a chain reaction of nuclear fission. By definition, fissile materials can sustain a chain reaction with neutrons of any energy. The predominant neutron energy may be typified by either slow neutrons or fast neutrons...
, relatively long half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
isotope 239Pu
Plutonium-239
Plutonium-239 is an isotope of plutonium. Plutonium-239 is the primary fissile isotope used for the production of nuclear weapons, although uranium-235 has also been used and is currently the secondary isotope. Plutonium-239 is also one of the three main isotopes demonstrated usable as fuel in...
into other isotopes of plutonium
Isotopes of plutonium
Plutonium is an artificial element, except for trace quantities of primordial 244Pu, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. It was synthesized long before being found in nature, the first isotope synthesized being 238Pu in 1940....
that are less fissile or more radioactive.
Thermal-neutron reactors (today's nuclear power plant
Nuclear power plant
A nuclear power plant is a thermal power station in which the heat source is one or more nuclear reactors. As in a conventional thermal power station the heat is used to generate steam which drives a steam turbine connected to a generator which produces electricity.Nuclear power plants are usually...
s) can reuse reactor-grade plutonium only to a limited degree as MOX fuel
MOX fuel
Mixed oxide fuel, commonly referred to as MOX fuel, is nuclear fuel that contains more than one oxide of fissile material. MOX fuel contains plutonium blended with natural uranium, reprocessed uranium, or depleted uranium. MOX fuel is an alternative to the low-enriched uranium fuel used in the...
, and only for a second cycle; fast-neutron reactors, which are uncommon today, can use this or any other actinide
Actinide
The actinide or actinoid series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium.The actinide series derives its name from the group 3 element actinium...
material indefinitely.
The degree to which reactor-grade plutonium is less useful than weapons-grade plutonium for building nuclear weapon
Nuclear weapon
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. Both reactions release vast quantities of energy from relatively small amounts of matter. The first fission bomb test released the same amount...
s is debated, with many sources saying it is difficult or impossible, and others saying it is relatively easy with modern technologies like fusion boosting to overcome predetonation, remote manipulation for assembly of highly radioactive components, and cooling of the pit during storage to offset accumulation of decay heat
Decay heat
Decay heat is the heat released as a result of radioactive decay. This is when the radiation interacts with materials: the energy of the alpha, beta or gamma radiation is converted into the thermal movement of atoms.-Natural occurrence:...
.
Classification by isotopic composition
| <1976 | >1976 | |
|---|---|---|
| <7% | Weapons grade | |
| 7-19% | Reactor grade | Fuel grade |
| >19% | Reactor grade | |
The difference is important in assessing significance in the context of nuclear proliferation
Nuclear proliferation
Nuclear proliferation is a term now used to describe the spread of nuclear weapons, fissile material, and weapons-applicable nuclear technology and information, to nations which are not recognized as "Nuclear Weapon States" by the Treaty on the Nonproliferation of Nuclear Weapons, also known as the...
.
Reprocessing
Nuclear reprocessing
Nuclear reprocessing technology was developed to chemically separate and recover fissionable plutonium from irradiated nuclear fuel. Reprocessing serves multiple purposes, whose relative importance has changed over time. Originally reprocessing was used solely to extract plutonium for producing...
of LWR (PWR
Pressurized water reactor
Pressurized water reactors constitute a large majority of all western nuclear power plants and are one of three types of light water reactor , the other types being boiling water reactors and supercritical water reactors...
or BWR) spent fuel recovers reactor grade plutonium (as defined since 1976), not fuel grade.
The DOE
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...
definition of reactor grade plutonium
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...
changed in 1976. Up until 1976, two grades were recognised:
Weapons grade, less than 7% Pu-240
Plutonium-240
Plutonium-240 is an isotope of the metal plutonium formed when plutonium-239 captures a neutron. About 62% to 73% of the time when Pu-239 captures a neutron it undergoes fission; the rest of the time it forms Pu-240. The longer a nuclear fuel element remains in a nuclear reactor the greater the...
and
Reactor grade, 7% or more Pu-240.
From 1976, three grades were recognised:
Weapons grade, less than 7% Pu-240,
Fuel grade, 7% to 19% Pu-240 and
Reactor grade, more than 19% Pu-240.
Reactor-grade plutonium nuclear test
The reactor grade plutonium nuclear test was a low-yield (under 20 kilotons) undergroundUnderground nuclear testing
Underground nuclear testing refers to test detonations of nuclear weapons that are performed underground. When the device being tested is buried at sufficient depth, the explosion may be contained, with no release of radioactive materials to the atmosphere....
nuclear test using non-weapons-grade
Weapons-grade
A weapons-grade substance is one that is pure enough to be used to make a weapon or has properties that make it suitable for weapons use. Weapons-grade plutonium and uranium are the most common examples, but it may also be used to refer to chemical and biological weapons...
plutonium
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...
, conducted at the US Nevada Test Site
Nevada Test Site
The Nevada National Security Site , previously the Nevada Test Site , is a United States Department of Energy reservation located in southeastern Nye County, Nevada, about northwest of the city of Las Vegas...
in 1962. Some information regarding this test was declassified in July 1977 under instructions from President Jimmy Carter
Jimmy Carter
James Earl "Jimmy" Carter, Jr. is an American politician who served as the 39th President of the United States and was the recipient of the 2002 Nobel Peace Prize, the only U.S. President to have received the Prize after leaving office...
as background to his decision to prohibit nuclear reprocessing
Nuclear reprocessing
Nuclear reprocessing technology was developed to chemically separate and recover fissionable plutonium from irradiated nuclear fuel. Reprocessing serves multiple purposes, whose relative importance has changed over time. Originally reprocessing was used solely to extract plutonium for producing...
in the USA.
The plutonium used was manufactured in a Magnox reactor in the United Kingdom, and provided to the US under the 1958 US-UK Mutual Defence Agreement
1958 US-UK Mutual Defence Agreement
The 1958 US–UK Mutual Defence Agreement is a bilateral treaty between the United States and the United Kingdom on nuclear weapons cooperation.It was signed after the UK successfully tested its first hydrogen bomb during Operation Grapple. While the U.S...
. Its isotopic composition has not been disclosed, other than the description reactor grade and it has not been disclosed which definition was used in describing the material for this test as reactor grade. The plutonium was apparently sourced from the military Magnox reactors at Calder Hall or Chapelcross. The content of plutonium-239
Plutonium-239
Plutonium-239 is an isotope of plutonium. Plutonium-239 is the primary fissile isotope used for the production of nuclear weapons, although uranium-235 has also been used and is currently the secondary isotope. Plutonium-239 is also one of the three main isotopes demonstrated usable as fuel in...
in material used for the 1962 test is estimated to have been at least 85%, much higher than typical spent fuel from currently operating reactors.
Reuse in reactors
Fast neutron reactorFast neutron reactor
A fast neutron reactor or simply a fast reactor is a category of nuclear reactor in which the fission chain reaction is sustained by fast neutrons...
s can use plutonium of any isotopic composition.
Reprocessing was planned in the 1960s when planners expected the uranium market
Uranium market
The uranium market, like all commodity markets, has a history of volatility, moving not only with the standard forces of supply and demand, but also to whims of geopolitics. It has also evolved particularities of its own in response to the unique nature and use of this material.The only significant...
to become tight and fast breeder reactors to be needed to efficiently use uranium supplies. This became less urgent with reduced demand forecasts and increased uranium supplies, and commercial deployment of fast reactors was postponed.
Today's thermal reactor
Thermal reactor
A thermal reactor is a nuclear reactor that uses slow or thermal neutrons. Most power reactors are of this type. These type of reactors use a neutron moderator to slow neutrons until they approach the average kinetic energy of the surrounding particles, that is, to reduce the speed of the neutrons...
s can reuse plutonium to a limited degree as MOX fuel
MOX fuel
Mixed oxide fuel, commonly referred to as MOX fuel, is nuclear fuel that contains more than one oxide of fissile material. MOX fuel contains plutonium blended with natural uranium, reprocessed uranium, or depleted uranium. MOX fuel is an alternative to the low-enriched uranium fuel used in the...
. Some reactors limit MOX fuel to a fraction of the total fuel load for nuclear stability reasons. Only the odd-mass isotopes of plutonium
Isotopes of plutonium
Plutonium is an artificial element, except for trace quantities of primordial 244Pu, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. It was synthesized long before being found in nature, the first isotope synthesized being 238Pu in 1940....
are fissile
Fissile
In nuclear engineering, a fissile material is one that is capable of sustaining a chain reaction of nuclear fission. By definition, fissile materials can sustain a chain reaction with neutrons of any energy. The predominant neutron energy may be typified by either slow neutrons or fast neutrons...
with thermal neutrons, and the even-mass isotopes accumulate. Plutonium-240
Plutonium-240
Plutonium-240 is an isotope of the metal plutonium formed when plutonium-239 captures a neutron. About 62% to 73% of the time when Pu-239 captures a neutron it undergoes fission; the rest of the time it forms Pu-240. The longer a nuclear fuel element remains in a nuclear reactor the greater the...
is a fertile material
Fertile material
Fertile material is a term used to describe nuclides which generally themselves do not undergo induced fission but from which fissile material is generated by neutron absorption and subsequent nuclei conversions...
like uranium-238
Uranium-238
Uranium-238 is the most common isotope of uranium found in nature. It is not fissile, but is a fertile material: it can capture a slow neutron and after two beta decays become fissile plutonium-239...
, becoming plutonium-241
Plutonium-241
Plutonium-241 is an isotope of plutonium formed when plutonium-240 captures a neutron. Like Pu-239 but unlike 240Pu, 241Pu is fissile, with a neutron absorption cross section about 1/3 greater than 239Pu, and a similar probability of fissioning on neutron absorption, around 73%. In the non-fission...
on neutron capture, but plutonium-242
Plutonium-242
Pu-242 is one of the isotopes of plutonium, the second longest-lived, with a half-life of 373,300 years.242Pu's halflife is about 15 times as long as Pu-239's halflife; therefore it is 1/15 as radioactive and not one of the larger contributors to nuclear waste radioactivity.242Pu's gamma ray...
both has a low neutron capture
Neutron capture
Neutron capture is a kind of nuclear reaction in which an atomic nucleus collides with one or more neutrons and they merge to form a heavier nucleus. Since neutrons have no electric charge they can enter a nucleus more easily than positively charged protons, which are repelled...
cross section
Neutron cross-section
In nuclear and particle physics, the concept of a neutron cross section is used to express the likelihood of interaction between an incident neutron and a target nucleus. In conjunction with the neutron flux, it enables the calculation of the reaction rate, for example to derive the thermal power...
, and would require 3 neutron capture
Neutron capture
Neutron capture is a kind of nuclear reaction in which an atomic nucleus collides with one or more neutrons and they merge to form a heavier nucleus. Since neutrons have no electric charge they can enter a nucleus more easily than positively charged protons, which are repelled...
s before becoming a fissile nuclide.
External links
- Reactor-Grade Plutonium Can be Used to Make Powerful and Reliable Nuclear Weapons, FASFasFas can mean the following:* Fas receptor, an important cell surface receptor protein of the TNF receptor family known also as CD95, that induces apoptosis on binding Fas ligand.* Fes, Morocco, the third largest city in Morocco, as an alternate spelling...
, Richard Garwin, CFRCFRCFR can refer to:* Code of Federal Regulations of the United States* Council on Foreign Relations, U.S. foreign policy think tank* Campaign finance reform in the United States* Cost and Freight, word used in international commerce...
, Congressional testimony, 1998 - Reactor-Grade and Weapons-Grade Plutonium in Nuclear Explosives, Canadian Coalition for Nuclear Responsibility
- Nuclear weapons and power-reactor plutonium, Amory B. Lovins, February 28, 1980, NatureNature (journal)Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...
, Vol. 283, No. 5750, pp. 817–823 - Additional Information Concerning Underground Nuclear Weapon Test of Reactor-Grade Plutonium