modified its procedures to prevent this type of accident.
As a result of this accident, the THORP was closed from April 2005 to July 2007 and will be finally closed in 2018 after the completion of contracts, and then dismantled.
2.2.4.4. Accident in Russia in September 2017
The IRSN [IRS 17c], as well as several Western European networks, have detected high concentrations of ruthenium 106 in the air. In France, the maximum concentration was measured in Nice between October 2 and 9, 2017 (46 μBq.m−3). By reverse modeling, the IRSN estimated that the accident site was located between the Volga and the Urals rivers and the date was the last week of September 2017. The quantity released was significant, in the range of 100–300 TBq. With 106Ru being an artificial fission product, three accidental sources are possible: first, leakage came from a spent fuel reprocessing plant; second, leakage came from a ruthenium-based radioactive source manufacturing plant; third, it could even be from the possible fall of a satellite powered by a nuclear reactor based on this radionuclide. With the final hypothesis being refuted by the IAEA, one of the other two possibilities is the most likely. The accident site is close to the Mayak complex, where the Kyshtym military accident occurred [AMI 19].
2.3. Accidents in laboratories
2.3.1. Chalk River laboratories
Of the nuclear accidents that have occurred in research laboratories, those at the Chalk River Laboratories are the most serious. The nuclear laboratories at Chalk River, Ontario, Canada, were established in 1942 as a result of British-Canadian collaboration. Their main activity is research in the field of nuclear reactions. In 1947, the first nuclear reactor outside the United States was commissioned. This nuclear research reactor, NRX (1947–1992), is moderated by heavy water and cooled by light water and was originally designed for military applications. Today, the Chalk River Laboratories are of great importance in the medical applications of nuclear energy.
The first accident occurred on December 12, 1952 in the NRX reactor. While the reactor was operating at full power, it experienced a partial loss of coolant. Operators made several bad decisions, causing a chain reaction that more than doubled the nuclear reactor’s power. In particular, operators opened valves in the cooling system to lower the containment pressure. Inexplicably, the descent of the control rods into the reactor core was not complete. This triggered an explosion that destroyed the nuclear reactor’s core and caused a nuclear fuel leak. A series of hydrogen explosions raised the four-ton dome into the air. About 370 TBq of fission products were released into the atmosphere with 4,500 tons of contaminated water. The contaminated water had to be pumped out of the subsoil and into shallow trenches near the Ottawa River. The core of the NRX reactor that could not be decontaminated had to be buried like other radioactive wastes. This accident was classified as a level 5 accident according to the INES. The Atomic Energy of Canada Company restarted the site within the year.
A second accident in 1958 involved a fuel failure and fire in the 135 MWt National Research Universal reactor (NRU) building (1957–2018). Some fuel rods had overheated. Using a robotic crane, one of the uranium metal rods was removed from the reactor vessel. But when the crane arm moved away from the core, the uranium caught fire, the rod broke and most of the stem fell into the containment. This led the whole building to be contaminated. The ventilation system valves were opened and a large area of the building’s exterior was contaminated. The fire was extinguished by scientists and cleaners wearing protective clothing by throwing buckets of wet sand.
2.3.2. French study centers
France has more than 70 basic civil nuclear facilities (INBs): “Laboratories, Plants, Dismantling Facilities and Waste Treatment, Storage or Storage Facilities” called LUDDs. Unlike the nuclear power plants operated by EDF, LUDD-type installations are very diverse (nature of activities, nature of risks) and are operated by many companies, the main ones being Areva (now Orano), CEA, ANDRA and EDF [IRS 09b]. The safety of nuclear installations is never definitively established and it should be aimed at continuous improvement, taking into account new knowledge and feedback. The IRSN also regularly capitalizes, using appropriate tools, on the feedback from the analysis of events that occurred in France in LUDD-type installations as well as the most significant incidents that occurred abroad in installations of the same type.
From the overall examination of the events reported for the years 2005–2008, it first appears that there was a significant increase (approximately 45%) in the number of events reported to the ASN in 2008 compared to that in the previous 3 years. In terms of consequences, it appears first of all that no events reported to the ASN for the years 2005–2008 had any serious consequences for workers, the public or the environment [IRS 09b]. ASN [ASN 12] has devoted an issue of the journal Contrôle to this subject.
Among the incidents that have occurred in nuclear study centers (CENs), some can pollute the aquatic environment. Thus, in 1974, the Grenoble center contaminated the groundwater with radioactive antimony, but the expertise that established that the maximum allowable concentration (MAC) had been exceeded is disputed by the center’s management. The use of radioactive sources gives rise to too many incidents or even accidents resulting from their escape into the environment and their recovery by the public, unaware of their danger. For example, the ASN was informed by a letter dated September 7, 2007 by the CEN in Saclay of the loss of a source of promethium 147 as part of a dust measuring device, the dismantling of which had been initiated in June 2006. Accidents related to radioactive sources will be discussed in more detail in Chapter 5.
When the CEN plutonium technology workshop (ATPu) at Cadarache (Bouches-du-Rhône) was dismantled in 2009, the French Atomic Energy Commission (CEA) considered that the residual dust deposits at the end of operation were significantly underestimated. Indeed, this workshop contained some 39 kg of plutonium, and not 8 kg, as initially assessed by the CEA. The ASN was only informed of this undervaluation on October 6, 2009, although the facts had been known since June of the same year. It classified the incident as a level 2 and suspended the dismantling of the ATPu for several months [AMI 13a].
2.4. Other accidents
2.4.1. Accidents in civil engineering
Accidents in the field of civil engineering are varied. Of the 81 civilian underground nuclear explosions (PUNE – Peaceful Underground Nuclear Explosions) carried out by the Soviets from 1965 to 1988, four (Globus-1, Taiga, Crystal and Kraton-3) resulted in accidents with long-term environmental contamination. The most dramatic and severe is the “Kraton-3” carried out in 1978 near the Arctic Circle (65.9°N, 112.3°E) in Yakutia (Republic of Sakha). Two radionuclides (137Cs and 90Sr) were particularly monitored in the environment, particularly in plants [RAM 09].
2.4.2. Accidents in nuclear propulsion
Propulsion using nuclear reactors is not limited to military applications. Various ships and civilian satellites are equipped with various types of engines in order to move. Accidents have also occurred.
Thus, spacecraft equipped with radioisotope power reactors or generators can contaminate aquatic environments directly by intact re-entry into the atmosphere and loss at sea, such as the generator of the lunar module used in the Apollo 13 lunar program (238Pu – 1.6.1015 Bq), which fell back in April 1970 into the South Pacific Ocean to a depth of about 6,100 m (USAEC, 1971, in [EIS 73]). Contamination of aquatic environments can be indirect, as in the case of the SNAP 9A series satellite, which vanished when it re-entered the atmosphere in 1964. Its power generator consisted of 629.1012 Bq of 238Pu. Up until then, 238Pu in the upper atmosphere
