RU2133062C1 - Method for decommissioning, recovery, intermittent disposal, and burial of nuclear- powered water craft with radioactive reactor compartments - Google Patents

Abstract

FIELD: decommissioning of nuclear-powered water craft. SUBSTANCE: method involves removal of fuel assemblies followed by comprehensive engineering inspection of reactor for condition of its vessel, pieces of equipment, and systems, as well as for possibility of removing radioactive wastes from reactor room. Mechanisms and pieces of equipment are dismounted and removed. Solidifying mixture is placed when afloat in radioactive compartment while holding water craft on even keel. Then radioactive compartment and two adjacent compartments are cut out, made buoyant, and kept afloat for the time being. For final burial of radioactive compartment, the latter is cut out and conveyed to burial site. EFFECT: improved safety, dispensing with extra capital outlays for procedures. 1 dwg

Description

 The invention relates to nuclear engineering, in particular to the disposal, temporary storage and disposal of objects with radiation hazardous waste.

 For the disposal of solid radioactive waste, various methods and methods are used, which are often associated with local conditions.

 The most commonly used methods.

 Packaging of low-level solid waste from laboratories in steel drums and burial of drums in trenches or pits such as alveoli, which are then covered with earth or poured with concrete about 200 mm thick.

 Packing waste of high radioactivity in steel drums with pouring concrete into the drum and dumping them in the ground or in deep mines.

 Packing glass vessels with liquid or solid waste of medium activity and steel cans with solid waste in steel drums filled with concrete, and dumping them into the sea.

 Loading highly active solid and liquid wastes into segments of plastic pipes with a diameter of 150 mm (the ends of which are welded) or into polyethylene containers with a capacity of 0.5 l, moreover, liquid wastes are cured by cement, loading pipes and containers into concrete boxes and dumping them into the sea.

Preliminary crushing and compaction of solid waste by pressing, packaging of waste thus treated in concrete blocks with a capacity of about 1 m ³ , pouring concrete into blocks and dumping them into the sea (see Spitsyn G.Ya. Processing and disposal of radioactive waste from laboratories. -M .: Atomizdat , 1965, p. 15, Fig. 2 and 3).

 Not all of the listed methods for the disposal and disposal of radioactive waste can be considered economically feasible and acceptable from a sanitary point of view. Absolutely unacceptable is the disposal of liquid waste in water bodies, in particular at sea. Despite numerous attempts in various countries (Russia, USA, England, Canada), it was not possible to prove the safety of such discharges.

 The method of liquid waste disposal in deep wells and closed geological formations is still under investigation, but it can be considered encouraging.

 However, the safest methods are based on the processing of liquid waste with the aim of removing concentrated products for disposal and returning the treated water for reuse. This method is widely used in Russia at facilities where there are large amounts of water of medium and low activity, for example, in large laboratories, industries and in centralized waste processing plants.

 Solid waste disposal at sea cannot be considered safe, as the possibility of erosion of the waste is not ruled out.

 It is better to use methods of organized burial in the ground in various trenches, pits, caves, in the presence of conditions that preclude penetration of underground surface and atmospheric waters to the burial site.

 It should be borne in mind that the processing of solid waste in order to reduce the volume of incineration, crushing, pressing due to imperfect methods and equipment is often economically inexpedient, since the savings in storages obtained by reducing the volume of waste are blocked by capital and operating costs waste processing, gas treatment, water treatment, etc. Waste treatment can only be justified if there is no territory for the construction of storage facilities. This is confirmed by the experience of the Aragon National Laboratory (USA), where waste incinerators with gas cleaning equipment were dismantled, because they turned out to be unprofitable.

 There is also known a method of packaging waste in sealed plastic or paper bags that are placed in transportable transport containers or loaded into cars and transported to landfills.

 In Russia, where so far more than 15 thousand tons of spent fuel has been accumulated, so far there is only one radiochemical reprocessing plant for nuclear waste (SNF) - RT-1. This plant processes spent fuel elements of the active zones of nuclear submarines (nuclear submarines), nuclear powered ships, research reactors and fast neutron reactors (RBI).

 Regenerated uranium is used in the production of fuel for RBMK reactors; plutonium is sent for temporary storage. Separate production facilities are provided for the reprocessing of spent nuclear fuel from VVEG N 1000 reactors.

 The reprocessing of spent nuclear fuel at RBMK reactors is considered economically inexpedient, and this fuel is stored under controlled conditions at the NPP sites until a decision is made on its disposal or safe disposal (see Popov V.K. "Nuclear Energy and Its Waste", Energy, 1995, No. 4, p. 5).

 The closest of our analogues was the US Department of the Navy’s report on the topic “Decommissioning, Disposal, and Disposal of USS Nuclear Submarines,” September 1993, which contains a program for the safe dismantling, disposal, and disposal of decommissioned nuclear submarines.

 The report contains information on the removal of nuclear fuel from the reactor, on the decommissioning of nuclear submarines, the removal of the reactor compartment for landfill, cutting of the remains of a submarine, on the disposal of residues with the selection of materials for reuse or sending them for disposal.

 The disadvantage here is that the boat has been in a dry dock for a long time, which significantly reduces the economic efficiency of the work and leads to high costs, also due to the fact that the issue of burying the compartments without dismantling them has not yet been resolved.

 The objective of the invention is the need to provide effective, safe, environmentally friendly and without additional capital costs decommissioning, disposal, temporary storage and disposal of objects with radiation hazardous compartments (ROO).

 The object means nuclear submarines, surface ships and ships with nuclear installations (cruisers, icebreakers), and auxiliary vessels - floating technical bases.

The specified result is achieved by the fact that between the unloading of spent fuel assemblies (SFA) and the dismantling of equipment, a comprehensive engineering survey (KIO) is carried out, including for the integrity of the hull, if necessary, reinforce the hull, then afloat, lay hardening mixtures in ROO with retention the facility on an even keel and subsequent sediment for at least 28 days, then either ROO is cut with temporary storage on the shore and followed by transportation to the place of its burial Ia or clipping ROO with giving it buoyancy and temporary storage afloat followed notch, transportation and burial in permafrost zone. The essence of the invention is illustrated by the following description and the accompanying drawing, which shows the stages of the proposed method:
stage A - integrated engineering survey (KIO);
Stage B - development of a detailed recycling project;
stage B - decommissioning of the facility;
Stage D - docking, installation of reinforcement for the hull;
Stage D - concreting of the radiation hazardous compartment (ROO) with special hardening mixtures at the berth afloat;
Stage E - Docking and cutting of concrete ROO:
option L,
option M;
stage G - temporary storage of ROO:
option L,
option M;
stage 3 - docking and cutting of the ROO;
stage I - reloading of radioactive waste to a crane and its transportation to the burial place;
stage K - unloading of radioactive waste to the shore at the place of burial;
1 - object;
2 - radiation hazardous compartment (ROO);
3 - route concrete pipelines;
4 - concrete mixer trucks;
5 - floating dock;
6 - concreted ROO;
7, 8 - adjacent compartments;
9 - concrete pumps with manipulators;
10 - crane ship;
11 - place of burial;
12 - temporary storage on shore.

 The method is as follows.

 Stage A. Integrated Engineering Survey (KIO).

 An engineering survey of the utilized object is carried out with the determination of the technical condition of its equipment and systems. Determine the possibility of removing radioactive waste (RW) from the premises of the facility.

 Stage B. Development of a detailed project for the disposal of the facility.

 The development project for the disposal of the facility is carried out specifically for each facility based on the KIO.

 Stage B. Decommissioning of the facility.

 Preparatory work.

 In designated areas, spent fuel assemblies (SFAs) are removed from reactors or storage facilities. SFAs that cannot be removed in a regular way must be removed using special devices and a cutting tool.

 An object with unloaded SFAs is towed to the selected technological berth and moored at it. According to the developed technology and to the sequence determined by the ship’s calculations of the designer, the removal of variable loads (fuel, fuels and lubricants, water, etc.) is carried out, dismantling of structures above the upper deck, preparation for fire work when installing hull reinforcements.

 The actual condition of the object clarifies the possibility of keeping it on an even keel. If necessary, the premises are determined in which mixtures or weights can be placed for trim of the object. They are being equipped and equipped with the necessary equipment, instruments, chemicals and personal protective equipment, radiation safety service, which ensures work at the facility.

 Stage G. Docking. Installation of reinforcements of the case.

 Docking of the object must be carried out in a floating dock. Reinforcement of the body is carried out in strict accordance with the project and the process.

 Stage D. Concreting ROO specially hardening mixes.

The main objective of this stage is to create the necessary number of engineering barriers of sufficient power, which should:
- provide the required safe level of dose rate on the external surface of special units;
- to exclude the migration of radionuclides outside the packaging within 75-100 years of their temporary storage.

Before starting work are checked:
Freedom of access on access roads to the parking lot of the facility 1.

 The presence of the required number of mixer trucks 4 for the delivery of mixtures and the possibility of their maneuvering at the pier.

 Correct placement and docking with object 1 of the primary and backup pumps for pumping the solution.

 Availability and availability of auxiliary equipment involved in the work (route concrete 3).

 Object 1 is moored at the pier.

 Laying the mixture in ROO 2 is carried out by the working team in accordance with the adopted technology.

 A special hardening mixture prepared at a concrete plant is delivered to the location of the facility. Delivery of a special hardening mixture is carried out using standard, commercially available concrete mixers 4. Supply and laying of mixtures is carried out using concrete pumps with manipulators 9.

 In the process of concreting, operational control of the draft, roll and trim of the object is carried out and the necessary differentiation occurs, i.e. keeping the object on an even keel using the systems of the object or by laying the necessary ballast in clean rooms or containers.

At the end of concreting:
- refine ship calculations based on the results of measurements of draft, trim, roll and the final differentiation of the object is carried out to ensure safe entry of the object into the dock;
- remove the general cartogram of the radiation situation at the facility;
- if necessary, additional concreting of the elements of the object;
- the object is settled in a designated place for at least 28 days to achieve the required concrete strength.

 Stage E. Docking and cutting of concreted ROO.

 These works, given the large mass of ROO 2, can be performed in the floating dock 5.

 Let's consider two options.

 Option L.

 After concreting the radiation-hazardous compartment (ROO) 2, the object is placed in the floating dock 5 and the extremities are cut, keeping compartments 7 on both sides of the concreted compartment 6 and for subsequent ensuring buoyancy of the ROO 6 (see step E). As such, concreted ROO 6 (packaging) is temporarily kept afloat at the berth (see step G).

 The main reason for placing concreted ROO 6 for temporary storage may be the lack of a constructed and appropriately equipped disposal site or, for example, the lack of transportation at this stage of time (see step G). An equally important factor is the observation of concreted ROO 6 during the first 10-15 years.

 Temporary storage for 10-15 years makes it possible to actively monitor the condition of the preservative and the packaging of ROO as a whole. For the same period of time, short-lived radionuclides decay and the radioactivity of the object is significantly reduced. During this period, it is possible to make, if necessary, any design changes to the packaging design. Further, with the advent of the possibility of transportation to the burial place, this temporarily stored concreted ROO 6 is again docked and full cutting of compartment 6 is performed, that is, parts 7 and 8 are cut, leaving only compartment 6 (see step H). Then it is loaded onto a crane crane 10 (see step I) and transported to the burial place 11 in the permafrost zone (see step K).

 The remains of the facility’s body are sent for disposal to Vtorchermet enterprises.

 Option M.

 After concreting ROO 6, the object is placed in a floating dock 5 and cut ROO (stage E) with temporary storage on shore 12 (stage G). In the presence of a constructed and suitably equipped landfill using a crane-ship 10, the concreted ROO 6 is reloaded (stage I) and transported to the place of burial 11 in the permafrost zone (stage K). The remains of the facility’s body are sent for disposal to Vtorchermet enterprises.

Main advantages:
1. All operations for the preparation of mixtures and filling them with concrete structures are fully mechanized.

 2. The use of the proposed method is highly reliable, as it is carried out by commercially available and practically used mechanisms.

 3. In the radiation hazardous area, only a short-term installation of a part of the technological chain (route concrete ducts 3) for laying mixtures is carried out, requiring minimal (it can be a matter of minutes) participation of maintenance personnel.

 4. Due to the lack of need for decontamination of radioactive facilities and equipment, the appearance of secondary pollution waters is completely absent.

 All basic operations will be performed when people are located outside the radiation hazard zone by remotely controlled mechanisms.

 The inventive features correspond to the prior art, as no solutions have been found that can effectively solve the problem.

 Based on the available information on the composition and production load of existing shipyards, naval bases and concrete mortar production plants, we can conclude that, without additional capital costs, it is possible to provide regular decommissioning, disposal, temporary storage and burial of radiation hazardous facilities every year .

 The proposed method is optimal and can ensure the normal functioning and safety of the disposal of facilities as a whole, taking into account the requirements of the IAEA.

 With this method, the weakness of one barrier can be compensated for by the restraining ability of other barriers, since it is generally accepted that the geological barrier plays the most important role in ensuring long-term security.

 The advantages of the proposed method also consist in the fact that it simplifies the technological chain of radioactive waste management, avoids costly processing of structures and the generation of secondary waste and the associated cumbersome treatment, conditioning and disposal of waste of various degrees of radioactivity.

Claims (1)

 The method of decommissioning, temporary storage and long-term disposal of facilities with radiation hazardous reactor compartments, which carry out the extraction of spent fuel assemblies, dismantle and unload the mechanisms and equipment, cut out the radiation hazardous compartment, transport it and bury it, characterized in that after the extraction process fuel assemblies conduct a comprehensive engineering survey of the facility, including the determination of the technical condition of the hull, equipment and systems, removal of radiation hazardous waste from the premises of the facility, hardening mixtures are placed in the radiation hazardous compartment afloat while keeping the object on an even keel, then the radiation hazardous compartment is cut with two adjacent compartments to give the cut out buoyancy and temporarily kept afloat, as well as the subsequent cutting of the radiation hazardous compartment with further transportation and burial.