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 (33,000 m) had been generated solely by earlier nuclear explosions, but 4 months after the accident, this 238Pu had increased significantly. By the end of 1970, 95% (592.1012 Bq) of the 238Pu from this satellite had fallen to the surface of the land and oceans. Previously, two other American satellites carrying a power generator (SNAP-3A – 238Pu – 59.2.1012 Bq series) launched in 1961 had vanished into the atmosphere. Similarly, the Soviet Cosmos-954 satellite was destroyed on January 24, 1978, and radioactive debris was introduced into part of Canada’s Far North into certain bodies of water such as Great Slave Lake in Fort Reliance Bay. Fission products were sought in lichens growing on the debris fallout zone (900 km x 45 km corridor) in the northern Canadian territories. The environmental impact was minimal [TAY 79].
2.5. Waste management incidents
Waste management incidents are few and far between. Among these, let us mention the explosion that occurred on Monday, September 12, 2011 at around 12 p.m. in the CENTRACO facility located in Marcoule, in the Gard, France (30). Operated by SOCODEI, this facility is dedicated to the processing and conditioning of low and very low level radioactive waste. The explosion occurred in the metallurgical furnace used to melt metal waste. One employee was killed and three others burned to varying degrees by a violent projection of molten metal in the facility’s hall. IRSN measurements confirmed the absence of radioactive releases to the environment off-site [IRS 12b].
There are also some risks associated with waste storage, such as leaks in tanks containing high-level liquid waste (e.g. Hanford mild steel tanks) [DET 74], which could lead to groundwater contamination. In the case of waste dumped at sea, contamination could result from a barrel crack (manufacturing defect) or corrosion, resulting in the release of radioactive materials. In France, at the Centre de Stockage des déchets à vie longue et haute activité de la Manche (CSM), stored tritium escaped into groundwater. Thus, between 1977 and 1992, tritium contamination reached values of 1.4.104–6.105 Bq.L−1 at different points from the slick