Ten Years of RRRFR Programme
A.V. Smirnov, S.V. Komarov, B.A. Kanashov, S.N. Komarov
Nuclear & Enviromental Safety, №1, 2013
The Russian Research Reactor Fuel Repatriation (RRRFR) programme has been on-going for a decade as part of the Global Threat Reduction Initiative. Its primary objective is to prevent proliferation of nuclear materials through consolidation and disposal of the existing stockpiles of highlyenriched uranium and conversion of research reactors to low-enriched nuclear fuel.
The danger that terrorists may get their hands on weapons of mass destruction had forced the United States government to organise shipments of highly-enriched uranium (HEU) fuel out of Kazakhstan (in 1994), Iraq (1993-1994) and Georgia (1998). These events, as well as realisation of how serious the problem really was, led to initiation in 1999 of the joint Russo-American programme to return Russian-made nuclear fuel back to the Russian Federation.
The programme was joined by 14 nations out of 17 that possess Russian-designed research reactors. Any country willing to return this kind of fuel to Russia was expected to shut the reactors down or upgrade them to be able to use low-enriched uranium (LEU) fuel. In its turn, Russia committed to provide physical protection, accounting and controls of the repatriated fuel material and refrain from using it for military purposes.
During 1999-2002, specialists commissioned by the IAEA, Russia and the United States undertook major efforts to prepare various research reactors for participation in the RRRFR programme. On 28 May 2004, Russia and the United States signed an agreement to cover cooperation between the two countries in shipping Russian-origin research reactor nuclear fuel back to the Russian Federation, providing the legal framework for programme implementation.
Numerous Russian organisations have since taken part in the RRRFR programme. All projects have been performed under Rosatom management and Rostekhnadzor supervision.
Non-irradiated fuel repatriation
Repatriation of non-irradiated nuclear fuel had started even before the cooperation agreement between the Russian and United States governments was signed. In August 2002, the first IAEA-organised shipment of non-irradiated fuel took place from the RA research facility at Vinča (Serbia, formerly Yugoslavia), as a result of which the Russian Federation received back about 50 kg of uranium, some of it HEU. The Russian firm Sosny acted as the main operator for this shipment, also providing the development, acceptance and approval of all required documentation in Russia. Since then, 20 more shipments of fresh nuclear fuel have been successfully completed, using Russian-made containers TK-S14, TK-S15 and TK-S16. All shipments were effected by air as this helps to avoid difficulties with transit countries by simplifying the logistics and customs clearance processes, as well as making provision of physical protection easier. In Russia, the cargoes were received by NIIAR and Luch. As a result of that effort, by the end of 2012 the world outside the Russian Federation was essentially cleared of any appreciable quantities of Russian-origin highly-enriched uranium or plutonium that could represent a potential terrorist threat.
Spent research reactor fuel repatriation
Import of spent fuel assemblies into the Russian Federation is associated with a range of other problems, often far more difficult to resolve (legal, economic, technical, administrative), and demands close cooperation between all participating organisations.
Russian laws impose very strict requirements on such projects. In particular, regulations contain a provision that after delivery of spent fuel to a reprocessing site, environmental conditions in the surrounding region must not only remain undeteriorated, but even become safer through implementation of a special environmental programme. Demonstration of this reduced overall risk of radiation exposure and improved level of environmental safety is to be made in the so-called "integrated project" package prepared by an authorised organisation – the Federal Nuclear and Radiation Safety Centre. Integrated project must be endorsed by a number of competent authorities and accepted by state environmental expert review, a positive conclusion from which gives the go-ahead to signing and implementation of a foreign trade contract (FTC).
During preparation of an FTC covering management of spent research reactor fuel, a major problem arises associated with agreeing the terms on which radwaste is to be returned to its country of origin. Relevant documentation is expected to describe the types, composition, physical form, quantity, and package of reprocessing products to be returned. The existing radiochemical process at Mayak envisages that liquid waste produced by reprocessing of spent fuel assemblies from various reactors and suppliers is to be mixed and temporarily stored together prior to conditioning. It is hence not possible to obtain conditioned radwaste with its radionuclide composition matching an exact batch of reprocessed SFAs.
It is essential that the amount of reprocessing products to be returned is determined using agreed-upon methods, based on the premise that the activity of imported fuel assemblies must be equivalent to that of reprocessing products. Criteria for such equivalence must be reconciled between the SFA supplier and receiver (the radiochemical facility). Sosny had suggested an ingenious method for establishing such equivalence of activity, which was first used during preparations for a Czech research reactor spent fuel import project and eventually adapted to be applied for spent fuel imports from other countries. Shipments of irradiated nuclear fuel were effected using Russian-made TUK-19 and Czech-made SKODA VPVR/M containers. All available modes of transport have been used: automobile, rail, river, sea, and air. As part of projects implemented within the framework of the programme, new or improved designs were developed of transport containers, spent fuel loading equipment, transport vehicles, as well as transport and handling processes involved with shipping.
Process and equipment used to load SFAs into TUK-19
During preparations for spent fuel shipment from the Romanian WWR-S Magurele (IFIN-HH) reactor it became obvious that a transfer cask was needed. In order to provide the level of safety demanded by the Romanian regulatory authority during spent fuel assemblies loading into the TUK-19, a special process was designed. Using a transfer cask fitted with an automatic gripper, the duration of loading/unloading of a type 50 basket containing spent fuel assemblies was limited to about one hour from the time an empty basket is taken out to the time the TUK-19 lid is secured.
After its successful deployment in Romania, the transfer cask was further adapted and used at the Serbian RA reactor to ship spent fuel from Vinca in 2010.
A transfer cask has currently been designed to be used for spent fuel loading into the SKODA VPVR/M overpack. The new process envisages that a special plate is used to ensure safety of the handling activities to move spent fuel assemblies from the transfer cask to the SKODA VPVR/M transport overpack. Previously, the SKODA VPVR/M could only be loaded from below, dictating that the container had to be placed above the cooling pool.
Ventilated canister for temporary storage and shipment of damaged spent fuel
Transport of damaged fuel requires application of special hardware. During the Serbian RA reactor de-fuelling project it became necessary to place the spent fuel into transport can- isters designed to support temporary pool storage, transportation and buffer storage at the reprocessing site.
In order to ensure safety of spent fuel shipment and storage, two difficult problems had to be addressed: preclude dangerous concentrations of potentially explosive hydrogen-oxygen mixes as radiolysis-produced hydrogen builds up, and prevent leakage of radioactive substances from the fuel material matrix into the environment.
In order to support shipment of spent RA fuel, special non-leaktight canisters were designed to provide the required level of explosion and fire safety. The canister is designed to let any produced hydrogen escape unobstructed, enable periodic venting of the canister cavity as it sits inside the overpack, as well as change the gas atmosphere. This technical solution was endorsed by the utility organisation, cask owners (NRI Rez and Mayak) and receiver of cargo (Mayak).
For prevention of radioactive substances leaking into the environment, a system of water treatment was built to provide the required level of radiation safety during pool storage of non-tight canisters at Vinca.
In the autumn of 2010, loading of canisters with spent fuel into TUK-19 and SKODA VPVR/M containers was completed, containers prepared for shipment, and required permits and licences secured. The transport route crossed three countries including sections covered by automobile, rail, and sea. In December 2010, the spent fuel was successfully delivered to Mayak.
Improved transport vehicles and routes
Extended time periods required to put in place the intergovernmental agreements to allow transit shipments by rail have forced the development of optimised transport routes and better transport vehicles.
In particular, shipment of spent fuel from the research reactor at the Institute of Nuclear Research of the Hungarian Academy of Sciences in Budapest involved sea transport for the first time in the RRRFR programme, effected by the Danish LYNX SNF-2 class vessel, equipped in accordance with the requirements of the International Code for the Safe Carriage of Packaged Irradiated Nuclear Fuel, Plutonium and High-Level Radioactive Wastes on Board Ships (INF Code). Observance of the requirements was verified by the Russian ASPOL-Baltic Concern. As most of the route lay outside the Russian national waters, the Russian certificate-permit included a provision concerning the use of international emergency maps in accordance with the requirements of the International Maritime Dangerous Goods Code. Particular attention was paid to transfer of responsibility for physical protection assurance: a special procedure was developed and approved.
After successful completion of the first shipment by sea, a decision was made to get domestic marine carriers involved with RRRFR transports. In 2008, the Krylov Shipbuilding Research Institute began its design efforts to re-fit for that purpose the MCL-Trader ship owned by ASPOL-Baltic. After completion of design development and approval, an Estonian shipyard was used to re-fit the ship under the supervision of representatives from the Russian Register of Shipping and certify her to the INF-2 class standard. The necessary ship documentation was written and approved, and the crew received specialist training and were issued with the appropriate permits. The MCL-Trader was then used for spent fuel removal from the Eva and Maria reactors in Poland in 2009; subsequent spent fuel shipments from Poland were effected using another Russian vessel, the Mikhail Dudin.
Transport package to support multimodal shipments of TUK-19
The Russian TUK-19 containers have traditionally been used for transport by rail on the TK-5 wagons, while their delivery to a rail station demanded development of special accessories. In order to ensure uniformity of the TUK-19 transport and handling operations, a special cargo container to accommodate it was needed.
The problem was solved under the project undertaken to remove spent research reactor fuel from Romania. The transport package for TUK-19 shipments was built upon the specialized heavy-duty 20-foot cargo container, which meets the requirements of the ISO standards, international conventions and industry regulations that govern dangerous goods shipments by various modes of transport. The container was fitted with a set of accessories to secure the TUK-19 inside.
During 2008, the Abakanvagonmash wagon works manufactured the first pilot prototype of this container, which was tested and issued with a certificate by the Head Office of the Russian Register of Shipping. The TUK-19 transport package underwent expert review by VNIIEF to verify observance of Russian and international requirements applicable to radioactive materials transport.
Creation of this transport package enabled the first shipment of spent fuel by air from Romania to take place in June 2009. Preparations for that shipment included production of extensive safety justifications for not just the package design, but also for the entire transportation process. Subsequently, this transport package was used for air shipments of spent fuel inside the TUK-19 from Libya (2009) and Uzbekistan (2012), as well as sea shipments from Serbia (2010) and Poland (2009, 2010 and 2012).
Overpack for radioactive material shipments by air
Creation of this transport package enabled air transports of a limited number of irradiated fuel assemblies inside type B packages. In order to support air shipments of radioactive materials without additional limitations imposed on activity levels, the RRRFR programme sponsored the development of a type C package on the basis of the SKODA VPVR/M container. Unlike type B packages, the type C must maintain its structural integrity and leaktightness when subjected to significantly stronger impacts.
The package design development began in 2009. Preliminary evaluations of various dynamic protection options were performed by VNIIEF. During the first stage of design development, a conceptual solution was adopted to build dismountable dynamic impact limiters in the form of spheres made of titanium alloy enclosed inside a cylindrical shell holding the SKODA VPVR/M container. This approach was further reflected in the design specification for type C package, which became known as TUK-145/C. Field tests of the prototype TUK-145/С behaviour hitting a target when moving at a speed of 90 m/s, as required for type C packages, were performed at the VNIIEF crash test facility.
In April 2012, a certificate-permit for the TUK-145/C was issued. Using Sosny-produced design documentation, the VSMPO-AVISMA titanium factory located in the Urals region of Russia manufactured the first impact limiter cover. In June 2012, further tests were carried out in Ulyanovsk Vostochny Airport to demonstrate feasibility of two methods for TUK-145/C re-loading from an automobile vehicle to An-124-100 airplane: one using a semi-trailer and another a rollertrack system with truck-mounted crane.
RRRFR programme extension to Russian facilities
In a logical continuation of the RRRFR programme it was extended to also cover the Russian nuclear installations that use highly-enriched fuel in line with the objectives of the Global Threat Reduction Initiative.
The decade of experience may well be of use on similar Russian facilities, and the equipment and technologies developed for the programme are already being applied for fuel shipments within Russia. An example of that was the “pilot” removal of spent fuel from the research reactors at Leipunsky Institute of Physics and Power Engineering. The site of the Institute holds a considerable amount of spent fuel previously used in research reactors and critical test rigs, as well as subjected to testing in “hot cells”, often rendering the fuel breached or damaged.
In order to prepare the spent fuel assemblies for shipment to a reprocessing facility, the following systems and equipment were developed, supplied and commissioned:
– leaktight canisters to accommodate both mis-shaped and normal VM spent fuel assemblies inside TUK-19 containers;
– leaktight canisters to accommodate spent AM fuel assemblies and individual fuel rods inside TUK-108/1 containers;
– a set of shielded cell equipment for handling of normal baskets, removal of spent fuel from the baskets, chipping-off VM fuel assembly heads to size, placement of VM fuel assemblies into canisters, as well as canister sealing.
The work to prepare for spent fuel removal from the Leipunsky Institute site started in 2009. First, a priority list was put together of spent fuel that could be accepted and processed by Mayak without any changes to its normal technological process. Certain upgrades were only made to the TUK-19 transport and handling process.
The choice of transport (by automobile to a transfer site and then by rail to Mayak) was dictated by the unsatisfactory condition of access rails from Obninskoye rail station to Leipunsky Institute site. Currently, work is under way to restore the access rail tracks.
Another example is the project undertaken at the Joint Institute for Nuclear Research in Dubna. To prepare for removal of nuclear materials therefrom, an inspection was carried out along with analysis of the potential methods of shipment. Relying upon the RRRFR experience it was suggested that spent fuel assemblies be transferred from the at-reactor storage facility to TUK-19 containers, with those in their turn being loaded into 20-foot ISO containers. Taking into account the actual physical condition of the HEU-materials (represented largely by chips and cut-offs) and in order to improve safety of transport in both normal and accident conditions it was deemed necessary to place the materials into custom-made leaktight canisters.
It should be noted that in Russia there are about a dozen organisations falling under various jurisdictions that possess research reactors and critical test rigs (a total of 117 installations), which hold a considerable stockpile of spent fuel. For this spent fuel to be removed and reprocessed, a coordinated effort is needed between a number of utilities, as optimization of budget costs reprocessing schedules makes it desirable that a common system of project management be adopted along with standardised equipment and transport and handling processes, as well as a standardised set of licensing documentation.
As a result of RRRFR programme implementation, the amount of HEU fuel brought back into the Russian Federation has totalled some 1,930 kg. Countries such as Latvia, Bulgaria, Romania, Libya, Serbia and Ukraine had their entire stockpiles of highly-enriched fuel removed.
The decade that has passed since the start of the programme demonstrated that consolidation of highly-enriched uranium fuel on an international scale is feasible if a coordinated effort between all stakeholders is made.
Количество просмотров: 1222