Comprehensive dismantlement of the Lepse technical floating base

Transcription

1 Comprehensive dismantlement of the Lepse technical floating base M. Kashka, Deputy Technical Director of the Nuclear Icebreaker Fleet, Murmansk Shipping Company, Russia 1. General specifications of the Lepse service ship Lepse is a service ship of the civilian atomic fleet which building began in 1934 but was not completed. Initially Lepse ship was intended to be used as a dry cargo boat. However, the ship had never been used as formerly designed. In 1961 the ship was taken into service by the Murmansk Shipping Company as a floating service base. From 1963 to 1981 Lepse provided refuelling on the Lenin, Arktika and Sibir ice-breakers. Since the Imandra service ship was commissioned the Lepse has been used for storing spent nuclear fuel, radioactive waste, tooling and equipment. Lepse is equipped with special-purpose storage facility for spent nuclear fuel (SNF), tanks for collection and interim storage of liquid radioactive waste (LWR) and the rooms intended to carry out service operations with reactor equipment. In 1988 Lepse was taken out of service and in 1990 was categorised as a laid-up ship, with the main engine kept operational. In 1999 a docking survey and repair of the ship was conducted. The survey showed that the wear of the hull did not exceed 16% with exception of the ship`s keel strake in the aft end of the ship and the bilge strake which are worn down to 29% at most (maximum allowable wear of the hull being 35%). Currently Lepse is moored at the Atomflot facility (a nuclear-powered ice-breakers fleet base) located outside the city of Murmansk. Safe architecture of the storage compartment and administrative and engineering arrangements ensure its safe and radiation safety. The ship is equipped with radiation monitoring sensors which transmit a generalized signal to the landbased radiation monitoring site (Lepse village). A shift team keeps watch over the ship by going hourly round the ship to monitor her overall safety. 2. Lepse spent fuel storage specifications The main nuclear and radiation hazard on Lepse is the storage of spent nuclear fuel. Storage dimensions are: - length m, - width m, - height m. The storage facility of Lepse consists of two compartments of 3.6 meters in diameter and 3.4 meters high. Each compartment has 366 canisters 67 mm in diameter and 4 caissons 500 mm in diameter (circuit A). From the outside the canisters and the caissons are cooled by water (circuit B). 1 Kashka-eng

2 The compartments for storing spent fuel assemblies are arranged in the room equipped with biological shielding. This room is a hollow parallelepiped, made of carbon steel covered on both sides with stainless steel plates. The wall of the biological shielding is mm thick. The capacity of the space between the compartments is 115 m 3. In 1991 it was encased in concrete mix for testing the method and building an extra engineering barrier. 3. Spent nuclear fuel The storage facility holds 639 spent fuel assemblies (SFA). As for the terms of storage, the SFA are distributed in the following way: - 37 years -- 34%, - 26 years -- 8%, - 23 years -- 58%. As for uranium-235 enrichment, the SFA are divided into two groups: - SFA of OK-150 (the first reactor plant on the Lenin icebreaker) with initial fuel enrichment of 6,5 % at most, - SFA of OK-900 with initial fuel enrichment of % at most. Average power generation: - 1 SFA of OK MWh, - 1 SFA of OK MWh. Parameters of the stored fuel Table 1 Characteristics Left Compartment Right Compartment SFA (639 pcs) OK OK canister caisson 5 13 Uranium-235, kg Plutonium-239, kg 8 - Fission products, kg β-activity, ТBq α-activity, TBq Residual power, kw It is necessary to check possibility of SFA movement the in the canisters in order to define whether SFA could be extracted using the standard technique. 2 Kashka-eng

3 Figure 1. Lepse service ship Basic specifications: Length, max - about 88.0 m Width, max - about 17.1 m Height, max - about 9.9 m Draught - about 6.5 m Water displacement, max - about 6100 t 3 Kashka-eng

4 Figure 2. Spent fuel storage Spent fuel storage facility Canistered SFA Biological shielding (steel) Storage compartment Concrete 4 Kashka-eng

5 Figure 3. Storage compartment with rotating plate Caisson Rotating plate Canister plug Circuit A Tube plate Biological shielding Circuit B Concrete Storage compartment Caisson Caisson Water discharge from circuit A Water drain from circuit B Inner Canistered SFA Tube plate Water Water feed to circuit 5 Kashka-eng

6 4. Radioactive waste 639 canisters of the right and the left storage compartments (circuit A) hold about 0.4 m 3 of liquid radwaste, total estimated activity of which is no less than TBq. The overtopping tank of the storage compartments holds 3 м 3 of liquid radwaste, total estimated activity of which is about TBq. The secondary circuit (circuit B) holds 48 m 3 of water (each tank containing 24.0 м 3 of water), with total activity of 2.0TBq. Tanks for collection and storage of liquid radwaste have been taken out of service. Radioactive sediments and contamination have been immobilized with special-purpose film coatings under the method provided by the ASPEKT Association. The sediment at the bottom of the tanks has been encased in concrete. The spent fuel storage contains 24 containers with solid radwaste (capacity is 36 m 3 ). 5. Radiation environment Gamma-radiation dose rate: - inside the storage compartment µsv/h at a distance of one meter from deck; - inside the rooms adjacent to the storage compartment µsv/h; - inside the controlled area at the aft µsv/h; - inside the process tanks rooms µsv/h - on the open decks in the controlled area µsv/h; - on the open decks in the monitored area µsv/h; - in the working area of the monitored area µsv/h; - inside the cabins µsv/h. In 2002 the ASPEKT Association carried out film decontamination and coating immobilization of the surfaces of the storage compartment and its equipment. As a result, radioactive contamination has reduced times and now is kbq/ m 2, and in other rooms of the controlled area does not exceed 15 kbq/m Background of the international project In 1994 on the initiative of the Norwegian environmental organization Bellona a pilot project for the overall remediation of the Lepse service ship was included in the Euro-Arctic Barents Region Working Programme, and in 1995 it was included in the programmes of the European Commission, thus, the Project was given an international standing. In within the TACIS Programme the Consortium of the French company SGN, and British AEA Technology prepared two reports describing an engineering concept of the Lepse 6 Kashka-eng

7 SNF management. This concept does not cover all technical issues concerning the unloading of all fuel from Lepse and her overall remediation. The Consortium should have prepared the «Safety Report and Environmental Impact Assessment Report of the Lepse Defuelling Project». However, only one «Basic Data» section was completed. Further financing of the work was terminated because of the Consortium's failure to carry out the «Environmental Impact Assessment Report of the Lepse Defuelling Project» to the required scope. In October 2000 a bilateral agreement was signed between l`agence Francaise de Development and Murmansk Shipping Company on financing the international defuelling project, and the same agreement was signed in July 2003 between the MSCO and the Nordic Environmental Financial Corporation (NEFCO). European Commission made a declaration on financing the Project in However, the funds have not been allocated. Estimated budget of the Project is Euro. It is broken down between the following international contributors: Norway NOK The Netherlands Euro European Commission Euro Agence Francaise de Development Euro MFA of France Euro NEFCO Euro In 2002 the Ministry of Transportation of the Russian Federation made a contribution of 50 million rubles to maintain the ship in environmentally safe condition. On October, 6, 2003 an agreement between SGN and MSCO was signed to develop a technical assignment (TZ) (for the preliminary design of the Lepse defuelling project), Investment Justification Report (OBIN) and Baseline Report. TZ and OBIN are the Project documents which must be produced prior to development of the preliminary design. These documents are to be developed in compliance with requirements of the Russian rules and regulations. SGN intended to involve Russian subcontractors to perform Technical Assignment and Investment Justification Report. But it failed to do that. The agreement came into force on March, 2, SGN failed to deliver the documents specified in the Agreement. The Agreement expired on November 2, The international contributors have allocated Euro for SGN`s services. Apart from the above-mentioned documents, a methodology is created under international financing to develop Russian regulatory documentation limited to the Lepse only. Expediency of development of a document concerning only one ship is in doubt. In our opinion, a common regulatory base regulating all the operations related to service ships remediation should be established. From experience of foreign companies in the Lepse project it comes clear that the organization of work used now is a deadlock that leads to waste of funds allotted for the project. Moreover, the Project documentation developed by a company without a Russian license cannot be submitted to Regulators for approval. On the instructions of Minatom of Russia in 2004 the ASPEKT Association established a consortium of Russian design and research organizations (VNIIPIET, AISBERG, RRC Kurchatov Institute, IBRAE, TsNIITS, EKOATOM and other). The Consortium is capable to 7 Kashka-eng

8 perform design work on the Lepse overall remediation in full compliance with Russian laws and regulations of Rostechnadzor of the Russian Federation. Successful experience of spent fuel unloading from PM-32 and PM-80 storage compartments similar to the Lepse ones in the Russian Far-East would be used. In order to work efficiently it is necessary to fund Russian organizations directly. That would exempt the Financing Contributors` funds from taxes in Russia. In order to make examination of project documentation it is necessary to involve foreign engineering companies. Several international projects are being implemented in such a way. 7. Proposals on the Project implementation At present, the most hazardous facilities for the environment of the Euro-Arctic region are the Northern Navy`s and civilian fleet service ships. There are 72 service ships both active and laid-up, including floating tanks for LWR storage. More than 50 ships have retired and are awaiting dismantlement. 28 of them are in emergency condition, sunken or half-sunken. At present, there is no technology approved and practically implemented that would enable dismantlement of such vessels. There is no long-term radwaste storage either capable to store radwaste generated after the ships dismantlement. Therefore, it is needed to solve a new task - arrange a safe storage afloat of service ships and their further dismantlement. The Russian design and research organizations (VNIIPIET, AISBERG, RRC Kurchatov Institute, TsNIITS, EKOATOM and other) have carried out preliminary study on the overall remediation of Lepse. Two options have been considered: - Option 1: spent fuel unloading, followed by cutting the ship into blocks and their disposal, - Option 2: cutting the ship into blocks, their disposal and spent fuel unloading. Two locations have been examined for conducting these operations: the Atomflot facility and the Nerpa Shipyard. Considering submarine decommissioning experience and a well-developed infrastructure to provide support for these operations, the Nerpa Shipyard has become the most preferable location. The second option to the Lepse handling is preferable. Its implementation would enable to eliminate the environmentally hazardous ship in a shortest possible time and defuel it with the storage compartment being in safe conditions ashore. 8 Kashka-eng

9 Towing of Lepse ship from Atomflot site to the Nerpa Shipyard Transfer of the ship up to a slipway Dismantlement of the ship's superstructure Cutting the ship into blocks followed by dismantlement of the engine and boiler compartment and superstructure Preparation of the SNF storage and the stern compartments of the ship for their transportation to the interim storage facility Transportation of the SNF storage and the stern compartments of the ship up to the slipway at the interim storage facility Storing the ship's SNF storage compartment and the stern compartment at the interim storage facility Remediation activities prior to SFA unloading from the ship Figure 4. Cutting Lepse into blocks at Nerpa Shipyard without preliminary unloading of spent fuel 9 Kashka-eng

10 Block 1 Block 2 Block 3 Block 4 Figure 5. Cutting the ship on to blocks 10 Kashka-eng

11 Weight and dimensions specifications of blocks Table 2 Block # Appellation Arrangement, Frame # Length, m Weight less ballast, tons 1 Superstructure (cabins, domestic compartments) 2 Stem block (SNF storage, controlled area) 3 Engine and Boiler Room Stern block with storage compartment Notes 1. Blocks # 2,3,4 maintain positive buoyancy 2. Blocks are to be dismantled if the immobilized radioactive contamination is below the regulatory requirements. Now it is proposed that: 1. Russian design and research organizations should develop: - a concept for Organisation of a safe storage afloat of naval and civilian service ships and their subsequent dismantlement, - Lepse remediation design documentation (to be implemented till 2009). 2. Assistance is to be requested from the GEG to involve foreign companies to conduct international peer review of the Lepse concept and the design documentation. 11 Kashka-eng