2.4 Radiation risks in naval reactors
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For each reactor type, there is an almost identical list outlining the risk of nuclear accidents or dangers in radiation exposed work. These lists are derived in various radiation protection documents, and outline procedures with the highest risk of exposure to ionising radiation.
Nuclear accidents may be characterised in their entirety under the following criteria:
1) Start and progress of an uncontrolled chain reaction2) Problems in cooling the reactor core
As a result of such an event, the crew could be exposed to higher than permitted doses of radiation or the fuel assemblies in the reactor could be damaged such that it can no longer be used.[169] Methods for preventing these kinds of situations are developed by the designers of the reactors, and the Navy is responsible for seeing that these rules are followed.
Included in the list of high risk operations are start up and shut down of the reactor, and routine procedures carried out while the reactor is running, such as taking hydraulic samples and water samples from the primary circuits. In addition, there is the risk of accidents during the monitoring of gases and the monitoring of functional and complex systems of control and safety.[170]
Past experience indicates that the most high risk work is in refuelling the reactor,[171] for the following reasons:
1) The work is done by many different people with varying levels of qualification for the work at hand;.2) Approximately 50 different technical operations are carried out during the process, 25 percent of which may potentially expose the operators to radiation.[172]
The most dangerous situations during the removal of spent nuclear fuel are as follows:
1) Disassembly and mounting of mechanisms for control and safety systems;2) Disassembly and mounting of the reactor lid;
3) Removal and replacement of fuel assemblies;
4) Refilling of primary circuits in the thermal system and testing of hydraulics;
5) Connecting, adjusting and checking of safety devices;
6) Manual checking for movement of the compensation register;
7) Reactor start up, measurement of neutrons and thermal measurements and checking.
All of the above-mentioned operations are executed by personnel at the shipbuilding yards and on the floating bases (the Project 326 M and 2020-Malina class) for the reloading and transport of spent nuclear fuel. Start up of the reactor is carried out by personnel from the physics laboratory, trained at the Kurchatov Institute. The most dangerous technical operation is the removal of the reactor lid. Experience from earlier accidents during this very procedure, indicates that this operation can unleash a nuclear accident with a significant release of radioactivity to the water and air over a large geographical area.[173]
In the 1990s, a safer method was developed for removing spent nuclear fuel from pressurised water reactors on submarines. First, the reactor tank is emptied of the water before the work begins. This water slows the neutrons inside the reactor. By removing the water from the tank, the risk of an uncontrolled chain reaction in the reactor core is reduced. The drawback with this method is that the level of radiation in the reactor compartment increases dramatically because there is no longer any water present to moderate the neutrons. Subsequently, extra measures must be taken to prevent the exposure of the workers to radiation. Hence this method of defuelling can only be carried out on submarines that have been laid up for a number of years whereby the level of radiation has decreased naturally.[174]
The construction and start up of new nuclear-powered submarines also entails operations involving risks of radiation exposure, as is also the case when restarting a reactor which has been in for repair or modernisation.
The operations entailing a risk of exposure to radiation are primarily:[175]
1) Installing the uranium fuel into the reactor;2) Mounting and adjusting the control and safety systems of the reactor;
3) Removing samples from the primary cooling circuit and the reactor core;
4) Starting up the reactor, and the first trial of equipment.
Other related high-risk operations:
1) Collection of radioactive waste during operation;2) Compression, sorting and burning of solid radioactive waste;
3) Temporary storage and transport of radioactive waste;
4) Deactivation of contaminated equipment and purification of radioactive gases.
Today, the start up of new naval reactors takes place at the shipyards in Severodvinsk. Newly refuelled reactors are started up at the shipyards on the Kola Peninsula or in Severodvinsk. Possible accidents will mainly contaminate the immediate surroundings near the nuclear submarine. Many of the shipbuilding yards are located close to densely populated areas. In Severodvinsk, there is a inhabited area only 400 metres away from the shipyard where operations involving hazards of radiation are carried out.
The risk of exposure to radiation during repair work, modernisation or the dismantling of inactive nuclear submarines, is two and a half times greater than during construction and normal operation of the submarines. This work generates four to five times more radioactive waste than during operation.[176] Accidents may occur during the removal and transport of the spent nuclear fuel from the reactors. The risk of accidents of criticality is great, for the containers of spent fuel assemblies may be damaged during reloading and transport. This could result in a release of radioactivity to the environment with the ensuing exposure to radiation of personnel and the civilian population.[177]
Most of the naval shipyards on the Kola Peninsula and in Severodvinsk that undertake this work are located near fairly densely populated areas.
2.4.1 Radiation safety agencies for nuclear-powered submarines
A number of organisations within the Navy and the Ministry of Defence are responsible for monitoring the safety of the reactors on board nuclear submarines. None of them come under the authority of a civilian regulatory authority.
OPB (FBS)-73 delegated the responsibility for supervising nuclear installations to three government agencies. Gosatomnadzor (Radiation Protection Authority) in the Soviet Union was charged with the responsibility of monitoring compliance with safety regulations and standards, especially with regard to the strength of constructions and the use of equipment and pipelines. The national Committee for Nuclear Power ensured that regulations governing nuclear safety were followed. The Ministry of Health monitored radiation safety regulations and procedures, ensuring that these standards were followed. There were routine checks to ensure that the crew on board nuclear submarines were not being exposed to undue amounts of radiation. Monitoring of safety procedures at nuclear power plants was not independent, since all three of the regulatory authorities fell under the auspices of the Council of Ministers of the Soviet Union. The main task of the Federal Committee for Nuclear Power was to encourage the use of nuclear power. Later Gosatomnadzor was developed (now the Federal Department of Nuclear and Radiation Safety).
The Ministry of Defence, which until the middle of the 1980s was responsible for approximately 200 nuclear reactors was not answerable to any of above-mentioned committees or ministries. It was not until 1979 that a department for nuclear safety was established in the Ministry of Defence, answerable to the Commander in Chief of the Navy (not even the Minister of Defence). In charge of inspections was Vice-Admiral N. Z. Bisovka. The Ministry of Defence's nuclear reactors and the nuclear facilities and complexes supporting these reactors have still not been placed under a federal authority in Russia; nor are they open to international inspection by the IAEA.
Safety procedures for nuclear reactors were re-evaluated following the Chernobyl accident (including within the Ministry of Defence). This resulted in a decision whereby inspections of nuclear safety would be carried out by the Ministry of Defence.
All supervision and control over nuclear installations and issues of nuclear safety were thereby given to the Ministry of Defence at all stages, from project development to decommissioning. New regulations of nuclear safety (RAS) PBYa(RAS)-13.08-88 were developed for the reactors of the submarines. Design bureau's and construction yards analysed both operative nuclear reactors and those under construction and planning with regards to modern safety requirements. Regulation No.332 which required that nuclear projects under construction be brought up to safety standards consistent with regulations, was adopted. The regulation concerned first and foremost the third generation of nuclear submarines (which were then under construction) and the fourth generation of nuclear submarines (which were under design).
Footnotes[169] Regulations concerning nuclear and radiation safety on naval nuclear energy installations. Return
[170] Sarkisov, A. A., Physical Basis for the Use of Nuclear Steam Producing Installations, Moscow. Return
[171] Severny Rabochy, June 3, 1993 Return
[172] Handbook for the firm GRTsAS. Presented to the Russian Government, Moscow, 1993. Return
[173] Atomnaya Energiya, No.2-1994. Return
[174] Information given on a pressconference in Severodvinsk, in connection with removal of spent nuclear fuel from the submarine with fabrication no. 401., march 1995. Return
[175] Handbook for the firm GRTsAS. Presented to the Russian Government. Moscow, 1993. Return
[176] Ibid. Return
[177] Ibid. Return
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