Regulatory Aspects

On the 19th of July 2001, the Belgian government approved a draft royal decree laying down new general regulations for the protection of workers, the public and the environment against the hazards of ionising radiation. The decree was signed by the King on the 20th of July and subsequently published in the Official Journal on the 30th of August 2001. The new regulations entered into force on the first of September 2001. They replace the Royal Decree of the 28th of February 1963.

Model of a Dry Storage Facility for a Medium Nuclear Power Plant

The intention was to model a dry storage facility that could satisfy the needs of a medium nuclear power plant similar to the NPP Krsko. The attention has been focused on radiation dose rate analyses and criticality calculations. Using the SCALE 4.4 code package and modified QAD-CGGP code, we modeled a facility that satisfies the basic criteria for public radiation protection. The capacity of the storage is 1,400 spent fuel assemblies which is adequate for a forty years medium NPP lifetime.

Operational Experience of TN 24 Dual Purpose Spent Fuel Storage Casks at the DOEL Nuclear Power Plants in Belgium

Spent nuclear fuel has been stored at the DOEL power station in Belgium in dual-purpose metal casks since 1995. The casks were procured from TRANSNUCLEAIRE by SYNATOM to meet the operational demands for on-site dry storage solutions for fuel arising from the four PWR reactors at DOEL. The TN 24 type of cask was chosen and a range of different cask types were developed. The initial requirement was for dual purpose cask to contain fuel from the DOEL units 3 and 4, these having similar fuel types but different lengths, and thus two new members of the TN 24 family were developed; the TN 24 D and TN 24 XL with capacities of 28 and 24 SFA’s. These casks were licensed as B(U) fissile packagings with approval certificates granted by the French and validated by the Belgium competent authorities for the transport configurations. Both cask designs were also analyzed by TRANSNUCLEAIRE in their storage configurations to ensure that the criteria for safe interim storage could be met. Since 1995, a total of 18 TN 24 D and TN 24 XL casks have been loaded with spent fuel assemblies with an average burn-up of 40,000 MWd/tU. SYNATOM subsequently decided to purchase further casks for DOEL 3 and 4 fuels with higher enrichments, higher burn-ups and shorter cooling times. TRANSNUCLEAIRE developed the TN 24 DH and TN 24 XLH casks within the similar envelope size and weight limits. The increase in performance was achieved by an in-depth optimization of each design in terms of radiation shielding, heat transfer and criticality safety. This paper shows how this optimization process was undertaken for the TN 24 DH and TN 24 XLH casks, 16 of which have been ordered by SYNATOM. DOEL 1 and 2 units use much shorter PWR fuel and it was decided to ship the fuel to unit 3 with an internal transfer cask because the handling limitations in the DOEL 1 and 2 pool prohibited the loading of a high capacity dual purpose transport/storage cask. The TN 24 SH cask was subsequently designed for DOEL 1 and 2 PWR fuel with a capacity of 37 assemblies and nine of there casks have been ordered by SYNATOM. The casks are fitted with monitoring devices to detect any change in the performance of the double metal O ring closure system and none of the casks has shown any deterioration in leaktightness. This paper examines the operation experience of loading and storing more than 30 TN 24 dual purpose casks and compares the performance with design expectations.

Last Developments About Spent Fuel Management in Belgium

In Belgium 57% of the electricity is presently generated by 7 nuclear units of the PWR type located in Doel and Tihange. Their total output amounts to 5632 MWe. Part of the spent fuel unloaded from the first three units has been sent till 2000 for reprocessing in the Cogema facility at La Hague. As the reprocessing of the spent fuel produced by the last four units is not covered by the contracts concluded with Cogema, Synatom, the Belgian utilities’ subsidiary in charge of the front- and back-end of the nuclear fuel cycle for all PWR reactors in Belgium, decided to study the possible solutions for a temporary storage of this spent fuel. End of 1993, the Belgian government decided that reprocessing (closed cycle) and direct disposal (open cycle) of spent fuel had to be considered as equal options in the back-end policy for nuclear fuel in Belgium. The resolution further allowed continued execution of a running reprocessing contract (from 1978) and use of the corresponding Pu for MOX in Belgian NPP’s, but requested a reprocessing contract concluded in 1990 (for reprocessing services after 2000) not to be executed during a five-year period. During this period priority was to be given to studies on the once-through cycle as an option for spent fuel management. Figure 1 is a chart showing the two alternatives for the spent fuel cycle in Belgium. In this context, Synatom entrusted Belgatom1 to develop a dedicated flask (called “bottle”) for direct disposal of spent fuel, to perform a design study of an appropriate encapsulation process and to prepare a preliminary feasibility study of a complete spent fuel conditioning plant. Meanwhile preparation works were made for the construction of an interim storage facility on both NPP sites of Doel and Tihange in order to meet increasing storage capacity needs. For selecting the type of interim storage facility, Belgatom performed a technical-economical analysis. Considerations of design and safety criteria as well as flexibility, reversibility, technical constraints, global economical aspects and construction time led to adopt dry storage with dual purpose casks (in operation since end 1995) for the Doel site and wet storage in a modular pool for the Tihange site (in operation since 1997). In parallel, ONRAF/NIRAS, the Belgian Agency for the management of radioactive waste and enriched fissile materials and the Belgian nuclear research centre, SCK•CEN, conduct underground investigations in view of geological disposal. The paper describes the methodology that Belgatom has developed to provide the utilities with appropriate solutions (reracking, dry storage in casks, wet storage in ponds, etc.) and how Belgatom demonstrated also the feasibility of spent fuel conditioning with a view to direct disposal in clay layers. The spent fuel storage facilities in operation in Belgium and designed and built by Belgatom are then briefly presented.

Safety and Uncertainty Analyses for the Shallow-Land Disposal of Radioactive Waste With Uranium Decay Chain

Safety and uncertainty analyses for the shallow-land disposal of radioactive wastes with uranium decay chain were performed using the deterministic and probabilistic safety assessment models. The deterministic analyses show that the dose calculation in residence scenario is of great importance owing to the influence of daughters built up by uranium decay chain. The parameter uncertainties for the important pathways in residence scenario are estimated from the probabilistic analyses using the statistical methodology. The uncertainty analysis indicates that the influence of parameter uncertainty is the most remarkable in the estimation for the inhalation of radon gas with residence.

Oxidation of Organic Radioactive Waste by Electrochemical Mediation

Liquid as well as solid organic radioactive waste can be processed by means of combustion. However, this method presents several well-known drawbacks including the corrosion of the ovens, the production of radioactive ashes and radioactive or toxic volatile products. The electrochemical mediation process is an excellent alternative to combustion, especially when dealing with hazardous materials such as explosives, pesticides, drugs and nuclear organic waste. Nevertheless, using the silver(II) species as electrogenerated mediator, requires to work in concentrated nitric acid media, which results, via its electrolysis, in a continuous NOx emission. The classical approach, using absorption columns and scrubbers to trap NOx, impairs the attractiveness of this process. Therefore the SCK•CEN has developed and patented an original method to suppress in-situ any formation of NOx, conferring the process mobility and compactness.

Utilization of Radioactive Waste for Solidifying Material to Fill Waste Forms

Minimizing the volume of radioactive waste generated during dismantling of nuclear power plants is a matter of great importance. In Japan waste forms buried in shallow burial disposal facility as low level radioactive waste (LLW) must be solidified by cement with adequate strength and must extend no harmful openings. The authors have developed an improved method to minimize radioactive waste volume by utilizing radioactive concrete and metal for mortar to fill openings in waste forms. Performance of a method to pre-place large sized metal or concrete waste and to fill mortar using small sized metal or concrete was tested. It was seen that the improved method substantially increases the filling ratio, thereby decreasing the numbers of waste containers.

Analysis of Waste Arisings From the Chernobyl Exclusion Zone

The paper reviews the findings of a recent international study to characterise the waste arising from the decommissioning of dumps in the Industrial Zone of the Chernobyl Nuclear Power Plant and the Exclusion Zone. Studied sites included the Industrial Zone outside the Sarcophagus, three engineered disposal sites (the so-called PZRO), non-engineered near surface trench dumps (PVLRO), contaminated soil and sites of ‘unauthorised’ disposal within the Exclusion Zone. The paper summarises the inventory of wastes, the management options, which have been considered for various dumps, and the resulting estimates of the volumes of waste streams, as well as the approach that was used in the decision-making process.

Demonstration and Licensing of a Spent Nuclear Fuel Dry Transfer System

Research studies by the Electric Power Research Institute (EPRI) established the technical and operational requirements necessary to enable the onsite cask-to-cask dry transfer of spent nuclear fuel. Use of the dry transfer system has the potential to permit shutdown reactor sites to decommission pools and provide the capability of transferring assemblies from storage casks or small transportation casks to sealed transportable canisters. Following an evaluation by the Department of Energy (DOE) and the National Academy of Sciences, a cooperative program was established between DOE and EPRI, which led to the cost-shared design of a dry transfer system (DTS). EPRI used Transnuclear, Inc., of Hawthorne, New York, to design the DTS in accordance with the technical and quality assurance requirements of the code of Federal Regulations, Title 10, Part 72 (10CFR72). EPRI delivered the final design report to DOE in 1995 and the DTS topical safety analysis report (TSAR) in 1996. DOE submitted the TSAR to the United States Nuclear Regulatory Commission (NRC) for review under 10CFR72 and requested that the NRC staff evaluate the TSAR and issue a Safety Evaluation Report (SER) that could be used and referenced by an applicant seeking a site-specific license for the construction and operation of a DTS. DOE also initiated a cold demonstration of major subsystem prototypes in 1996. After careful assessment, the NRC agreed that the DTS concept has merit. However, because the TSAR was not site-specific and was lacking some detailed information required for a complete review, the NRC decided to issue an Assessment Report (AR) rather than a SER. This was issued in November 2000. Additional information that must be included in a future site-specific Safety Analysis Report for the DTS is identified in the AR. The DTS consists of three major sections: a Preparation Area, a Lower Access Area, and a Transfer Confinement Area. The Preparation Area is a sheet metal building where casks are prepared for loading, unloading, or shipment. The Preparation Area adjoins the Lower Access Area and is separated from the Lower Access Area by a large shielded door. The Lower Access Area and Transfer Confinement Area are contained within concrete walls approximately three feet thick. These are the areas where the casks are located and where the fuel is moved during transfer operations. A floor containing two portals separates the Lower Access Area and the Transfer Confinement Area. The casks are located below the floor, and the fuel transfer operation occurs above the floor. The cold demonstration of the DTS was successfully conducted at the Idaho National Engineering and Environmental Laboratory (INEEL) as a cooperative effort between the DOE and EPRI. The cold demonstration was limited to the fuel handling equipment, the cask lid handling equipment, and the cask interface system. The demonstration included recovery operations associated with loss of power or off-normal events. The demonstration did not include cask receiving and lid handling; cask transport and lifting; vacuum/inerting/leak test; canister welding; decontamination; heating, ventilation, and air conditioning; and radiation monitoring. The demonstration test was designed to deliberately challenge the system and determine whether any specific system operation could adversely impact or jeopardize the operation or safety of any other function or system. All known interlocks were challenged. As in all new systems, there were lessons learned during the operation of the system and a few minor modifications made to ease operations. System modifications were subsequently demonstrated. The demonstration showed that the system operated as expected and provided times for normal fuel transfer operations. The demonstration also showed that recovery could be made from off-normal events.

Development of Commercial Technology for Remediation of Areas Contaminated With Radionuclides As a Result of Technogenic Activities

At VNIINM a facility was created to decontaminate soil and ground. The facility was tested using actual ground contaminated as a result of the CHERNOBYL accident that was brought from the BRYANSK region. At the initial ground contaminated with CS-137 to the degree of 1,6 bq/g the decontamination factor was 4–5. The practicability of the technology used in the facility for ground decontamination via hydroclassification has been demonstrated. The project of a commercial area remediation complex was designed having the throughput > 20 t/h contaminated soil.