Other accidents-1980s

1. Other accidents-1980s • March 13, 1980 –- Orléans, France - Nuclear materials leak • A brief power excursion in Reactor A2 led to a rupture of fuel bundles and a minor release (8 x 1010 Bq) of nuclear materials at the Saint-Laurent Nuclear Power Plant. The reactor was repaired and continued operation until its decommissioning in 1992. • March, 1981 - Tsuruga, Japan – Overexposure of workers • Overexposure of workers More than 100 workers were exposed to doses of up to 155 millirem per day radiation during repairs of a nuclear power plant, violating the company's limit of 100 millirems (1 mSv) per day. • September 23, 1983 Buenos Aires, Argentina - Accidental criticality • An operator error during a fuel plate reconfiguration in an experimental test reactor led to an excursion of 3×1017 fissions at the RA-2 facility. The operator absorbed 2000 rad (20 Gy) of gamma and 1700 rad (17 Gy) of neutron radiation which killed him two days later. Another 17 people outside of the reactor room absorbed doses ranging from 35 rad (0.35 Gy) to less than 1 rad (0.01 Gy). • April 26, 1986 — Prypiat, Ukraine (then USSR) - Power excursion, explosion, complete meltdown • A mishandled reactor safety test led to an uncontrolled power excursion, causing a severe steam explosion, meltdown and release of radioactive material at the Chernobyl nuclear power plant located approximately 100 kilometers north-northwest of Kiev. • May 4, 1986 – Hamm-Uentrop, Germany (then West Germany) - Fuel damage • A spherical fuel pebble became lodged in the pipe used to deliver fuel elements to the reactor at an experimental 300-megawatt THTR-300 HTGR. Attempts by an operator to dislodge the fuel pebble damaged its cladding, releasing radiation detectable up to two kilometers from the reactor. • November 24, 1989 — Greifswald, Germany (then East Germany) - Fuel damaged • Operators disabled three of six cooling pumps to test emergency shutoffs. Instead of the expected automatic shutdown a fourth pump failed causing excessive heating which damaged ten fuel rods. The accident was attributed to sticky relay contacts.

2. Other Accidents 1990s • April 6, 1993 — Tomsk, Russia – Explosion • A pressure buildup led to an explosive mechanical failure in a 34 cubic meter stainless steel reaction vessel buried in a concrete bunker under building 201 of the radiochemical works at the Tomsk-7 Siberian Chemical Enterprise plutonium reprocessing facility. The vessel contained a mixture of concentrated nitric acid, uranium (8757 kg), plutonium (449 g) along with a mixture of radioactive and organic waste from a prior extraction cycle. The explosion dislodged the concrete lid of the bunker and blew a large hole in the roof of the building, releasing approximately 6 GBq of Pu 239 and 30 TBq of various other radionuclides into the environment. The contamination plume extended 28 km NE of building 201, 20 km beyond the facility property. The small village of Georgievka (pop. 200) was at the end of the fallout plume, but no fatalities, illnesses or injuries were reported. The accident exposed 160 on-site workers and almost two thousand cleanup workers to total doses of up to 50 mSv (the threshold limit for radiation workers is 100 mSv per 5 years) • June, 1999 - Ishikawa Prefecture, Japan - Control rod malfunction • Operators attempting to insert one control rod during an inspection neglected procedure and instead withdrew three causing a 15 minute uncontrolled sustained reaction at the number 1 reactor of Shika Nuclear Power Plant. The Hokuriku Electric Company who owned the reactor did not report this incident and falsified records, covering it up until March, 2007. • September 30, 1999 — INES Level 4 - Ibaraki Prefecture, Japan - Accidental criticality • Workers put uranyl nitrate solution containing about 16.6 kg of uranium, which exceeded the critical mass, into a precipitation tank at a uranium reprocessing facility in Tokai-mura northeast of Tokyo, Japan. The tank was not designed to dissolve this type of solution and was not configured to prevent eventual criticality. Three workers were exposed to (neutron) radiation doses in excess of allowable limits. Two of these workers died. 116 other workers received lesser doses of 1 mSv or greater though not in excess of the allowable limit..

3. Other accidents -2000s • April 10, 2003 - Paks, Hungary - Fuel damaged • Partially spent fuel rods undergoing cleaning in a tank of heavy water ruptured and spilled fuel pellets at Paks Nuclear Power Plant. It is suspected that inadequate cooling of the rods during the cleaning process combined with a sudden influx of cold water thermally shocked fuel rods causing them to split. Boric acid was added to the tank to prevent the loose fuel pellets from achieving criticality. Ammonia and hydrazine were also added to absorb iodine-131. • April 19, 2005 — Sellafield, England, United Kingdom - Nuclear material leak • Twenty metric tons of uranium and 160 kilograms of plutonium dissolved in 83,000 literes of nitric acid leaked over several months from a cracked pipe into a stainless steel sump chamber at the Thorp nuclear fuel reprocessing plant. The partially processed spent fuel was drained into holding tanks outside the plant. • November 2005 — Braidwood, Illinois, United States - Nuclear material leak • Tritium contamination of groundwater was discovered at Exelon's Braidwood station. Groundwater off site remains within safe drinking standards though the NRC is requiring the plant to correct any problems related to the release. • March 6, 2006 — Erwin, Tennessee, United States - Nuclear material leak • Thirty-five liters of a highly enriched uranium solution leaked during transfer into a lab at Nuclear Fuel Services Erwin Plant. The incident caused a seven-month shutdown and a required public hearing on the licensing of the plant.