Tokai, Ibaraki
Encyclopedia
is a village
located in Naka District, Ibaraki
, Japan. It is approximately 120 km north of Tokyo
, Japan on the Pacific
coast.
As of 1 January 2005, the village has an estimated population
of 35,467 and a population density
of 946.29 persons per km². The total area is 37.48 km².
The Japan Atomic Energy Agency
along with other organizations currently operate a number of nuclear technology research facilities in the town.
Aside from nuclear facilities, Tokai has beaches. It is the sister city of Idaho Falls, Idaho, another town associated with nuclear energy
.
which occurred at the JCO nuclear reprocessing
plant on 30 September 1999, which killed two people.
The accident occurred when seven times the allowable limit of 18.8% enriched uranium dioxide
was mixed with nitric acid
in order to form uranyl nitrate
, and was put in a precipitation
tank to homogenize. At 10:35 am, when the seventh bucket (making a total of 16.6 kg of 18.8% enriched uranium
) was poured into the precipitation tank by three technicians, a blue flash of radiation occurred and the three technicians felt severe pain, nausea and had trouble breathing. The radiation alarms went off and the three technicians and their supervising technicians immediately left the building.
The criticality was stopped 20 hours later by draining the cooling water jacket around the precipitation tank and filling it with argon
, and purging the tank with boric acid
. The amount of neptunium
and plutonium
formed during the event was estimated through radiochemical analysis of the uranium solution from within the tank.
Two of the three technicians irradiated died on 22 December 1999 and 27 April 2000, respectively.
Villages of Japan
A is a local administrative unit in Japan.It is a local public body along with , , and . Geographically, a village's extent is contained within a prefecture....
located in Naka District, Ibaraki
Naka District, Ibaraki
Naka is a district of Ibaraki, Japan.Following the January 21, 2005 formation of the city of Naka, the district is coextensive with the village of Tōkai. As of January 1, 2005 population data, the district has an estimated population of 35,467 and a density of 946.29 persons per km²...
, Japan. It is approximately 120 km north of Tokyo
Tokyo
, ; officially , is one of the 47 prefectures of Japan. Tokyo is the capital of Japan, the center of the Greater Tokyo Area, and the largest metropolitan area of Japan. It is the seat of the Japanese government and the Imperial Palace, and the home of the Japanese Imperial Family...
, Japan on the Pacific
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
coast.
As of 1 January 2005, the village has an estimated population
Population
A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...
of 35,467 and a population density
Population density
Population density is a measurement of population per unit area or unit volume. It is frequently applied to living organisms, and particularly to humans...
of 946.29 persons per km². The total area is 37.48 km².
The Japan Atomic Energy Agency
Japan Atomic Energy Agency
The was formed October 1, 2005 by a merger of two previous semi-governmental organizations. While it inherited the activities of both PNC and JAERI, it also inherited the nickname of JAERI, "Genken" 原研, an abbreviated word for "nuclear research"....
along with other organizations currently operate a number of nuclear technology research facilities in the town.
Aside from nuclear facilities, Tokai has beaches. It is the sister city of Idaho Falls, Idaho, another town associated with nuclear energy
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...
.
- 1955 - Muramatsu-mura and Ishigami-mura merged into Tokai-mura
- 1956 - Japan Atomic Energy Research InstituteJapan Atomic Energy Research InstituteThe Japan Atomic Energy Research Institute is a former semi-governmental organization that existed for the purpose of further nuclear power in Japan. It was created June 1956 by the Atomic Energy Basic Law...
was set up at Tokai-mura
JCO radiation accident
Tokai was the scene of a nuclear criticality accidentCriticality accident
A criticality accident, sometimes referred to as an excursion or a power excursion, is an accidental increase of nuclear chain reactions in a fissile material, such as enriched uranium or plutonium...
which occurred at the JCO 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...
plant on 30 September 1999, which killed two people.
The accident occurred when seven times the allowable limit of 18.8% enriched uranium dioxide
Uranium dioxide
Uranium dioxide or uranium oxide , also known as urania or uranous oxide, is an oxide of uranium, and is a black, radioactive, crystalline powder that naturally occurs in the mineral uraninite. It is used in nuclear fuel rods in nuclear reactors. A mixture of uranium and plutonium dioxides is used...
was mixed with nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
in order to form uranyl nitrate
Uranyl nitrate
Uranyl nitrate is a water soluble yellow uranium salt. The yellow-green crystals of uranium nitrate hexahydrate are triboluminescent.Uranyl nitrate can be prepared by reaction of uranium salts with nitric acid...
, and was put in a precipitation
Precipitation (chemistry)
Precipitation is the formation of a solid in a solution or inside anothersolid during a chemical reaction or by diffusion in a solid. When the reaction occurs in a liquid, the solid formed is called the precipitate, or when compacted by a centrifuge, a pellet. The liquid remaining above the solid...
tank to homogenize. At 10:35 am, when the seventh bucket (making a total of 16.6 kg of 18.8% enriched uranium
Enriched uranium
Enriched uranium is a kind of uranium in which the percent composition of uranium-235 has been increased through the process of isotope separation. Natural uranium is 99.284% 238U isotope, with 235U only constituting about 0.711% of its weight...
) was poured into the precipitation tank by three technicians, a blue flash of radiation occurred and the three technicians felt severe pain, nausea and had trouble breathing. The radiation alarms went off and the three technicians and their supervising technicians immediately left the building.
The criticality was stopped 20 hours later by draining the cooling water jacket around the precipitation tank and filling it with argon
Argon
Argon is a chemical element represented by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table . Argon is the third most common gas in the Earth's atmosphere, at 0.93%, making it more common than carbon dioxide...
, and purging the tank with boric acid
Boric acid
Boric acid, also called hydrogen borate or boracic acid or orthoboric acid or acidum boricum, is a weak acid of boron often used as an antiseptic, insecticide, flame retardant, as a neutron absorber, and as a precursor of other chemical compounds. It exists in the form of colorless crystals or a...
. The amount of neptunium
Neptunium
Neptunium is a chemical element with the symbol Np and atomic number 93. A radioactive metal, neptunium is the first transuranic element and belongs to the actinide series. Its most stable isotope, 237Np, is a by-product of nuclear reactors and plutonium production and it can be used as a...
and 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...
formed during the event was estimated through radiochemical analysis of the uranium solution from within the tank.
Two of the three technicians irradiated died on 22 December 1999 and 27 April 2000, respectively.
External links
- http://f40.iaea.org/worldatom/Documents/Tokaimura/iaea-toac.pdfReport by the International Atomic Energy AgencyInternational Atomic Energy AgencyThe International Atomic Energy Agency is an international organization that seeks to promote the peaceful use of nuclear energy, and to inhibit its use for any military purpose, including nuclear weapons. The IAEA was established as an autonomous organization on 29 July 1957...
on the nuclear accident] - Official timeline of the nuclear accident