Interim Storage Facility Research Articles

Recognising interdependencies in design of nuclear fuel cycle and transportation of SNF and HLW

Spent nuclear fuel (SNF) discharged from a nuclear power plant and high level radioactive waste (HLW) generated during reprocessing SNF are typically stored at the sites where they are generated, often for prolonged periods of time. Eventually, however, these materials must be transported off-site to an interim storage facility, a reprocessing plant, or directly to a deep geologic repository. This paper considers the interdependencies between nuclear fuel cycle options and the transportation system, and argues that both must be addressed as part of an integrated system. Two examples are presented to illustrate why this is important. The first draws from experience gained during development of the US Department of Energy’s (DOE) program for disposing of SNF and HLW in a proposed repository. In particular, decisions DOE made with regard to waste package design had profound implications on the viability of the transportation system. The second example relates to operational changes now underway at nuclear po...

Aging management for long-term interim storage casks

AbstractThe aging management system for the mechanical components of nuclear power plants (NPPs) must be established and used by the licensee in such a way that the quality of safety relevant components is guaranteed for the completely designed lifetime of the NPP. This demands an extensive plant life management with special emphases on the knowledge of the degradation in material properties. The basic safety concept in Germany observes this circumstance. Lifetime extension of the German NPPs is an aim of the current valid coalition agreement of the German government. Operational extension of interim storage facilities requires, in comparison to the aging management system for NPP, an aging management system adapted to the special circumstances of spent fuel storage casks. Extension of interim storage periods for spent fuel casks beyond the designed lifetime requires, in comparison to the components of an NPP, an increasing knowledge of material degradation with potential impact on cask integrity, e.g. le...

Transport of large components in Germany – some experiences and regulatory aspects

AbstractAfter decommissioning of nuclear facilities, it is very often necessary to transport large components such as steam generators or reactor pressure vessels in public areas. In Germany, such shipments were carried out in 2007 and 2008 as follows: steam generators from the nuclear power plant (NPP) in Stade to Studsvik/Sweden by road and sea, reactor pressure vessel from the NPP in Rheinsberg to the interim storage facility near Greifswald by railway and steam generators from the NPP in Obrigheim to Greifswald, as well by road and inland waterway. The paper describes the experiences with these shipments, including radiation dose assessments to transport workers and the main aspects of the applied regulatory procedure by special arrangement, for which the Federal Office for Radiation Protection is the competent authority in Germany. A high level of safety was achieved for all the involved modes of transport (road, rail, sea and inland waterways). Based on these experiences, some regulatory aspects are...

Demonstration drop test and design enhancement of the CANDU spent fuel storage basket in dry storage facility

A dry interim storage facility has been constructed at the Wolsung power plant in Korea. This dry storage facility has seven separated modules. There are 40 long slender cylinders in one module. In one cylinder, ten baskets where sixty CANDU spent fuel bundles are loaded are stacked and stored. For this dry storage facility, analyses and tests for hypothetical accident conditions that might occur while moving and storing the baskets into a cylinder were performed. In a demonstration test, one of test basket models did not satisfy one of the safety-related requirements. Thus, the revised basket designs were generated using a structural evaluation based on finite element analyses and specimen tests. Among these revised designs, one design was chosen as a final revised basket design. The final revised design was the one creating the largest reduction of plastic strain in the upper welding region. It was also the one that required the smallest design change from the current basket design for easy adoption. Drop and leak tests were performed, and the final revised basket satisfied all performance requirements.

Cost comparisons of wet and dry interim storage facilities for PWR spent nuclear fuel in Korea

As a part of an effort to determine the ideal storage solution for pressurized water reactor (PWR) spent nuclear fuel, a cost assessment was performed to better quantify the competitiveness of several storage types. Several storage solutions were chosen for comparison, including three dry storage concepts and a wet storage concept. The net present value (NPV) and the levelized unit cost (LUC) of each solution were calculated, taking into consideration established scenarios and facility size. Wet storage was calculated to be the most expensive solution for a 1700 MTU facility, and metal cask storage marked the highest cost for a 5000 MTU facility. Sensitivity analyses on discount rate, metal cask price, operation and maintenance cost, and facility size revealed that the system price is the most decisive factor affecting competitiveness among the storage types.

Ageing management program for the Spanish low and intermediate level waste disposal and spent fuel and high-level waste centralised storage facilities

The generic design of the centralised spent fuel storage facility was approved by the Spanish Safety Authority in 2006. The planned operational life is 60 years, while the design service life is 100 years. Durability studies and surveillance of the behaviour have been considered from the initial design steps, taking into account the accessibility limitations and temperatures involved. The paper presents an overview of the ageing management program set in support of the Performance Assessment and Safety Review of El Cabril low and intermediate level waste (LILW) disposal facility. Based on the experience gained for LILW, ENRESA has developed a preliminary definition of the Ageing Management Plan for the Centralised Interim Storage Facility of spent Fuel and High Level Waste (HLW), which addresses the behaviour of spent fuel, its retrievability, the confinement system and the reinforced concrete structure. It includes tests plans and surveillance design considerations, based on the El Cabril LILW disposal facility.

ANALYSIS OF THE TRANSPORTATION LOGISTICS FOR SPENT NUCLEAR FUEL IN KOREA

As a part of the back-end fuel cycle, transportation of spent nuclear fuel (SNF) from nuclear power plants (NPPs) to a fuel storage facility is very important in establishing a nuclear fuel cycle. In Korea, the accumulated amount of SNF in the NPP pools is troublesome since the temporary storage facilities at these NPP pools are expected to be full of SNF within ten years. Therefore, Korea cannot help but plan for the construction of an interim storage facility to solve this problem in the near future. Especially, a decision on several factors, such as where the interim storage facility should be located, how many casks a transport ship can carry at a time and how many casks are initially required, affect the configuration of the transportation system. In order to analyze the various possible candidate scenarios, we assumed four cases for the interim storage facility location, three cases for the load capacity that a transport ship can carry and two cases for the total amount of casks used for transportation. First, this study considered the currently accumulated amount of SNF in Korea, and the amount of SNF generated from NPPs until all NPPs are shut down. Then, how much SNF per year must be transported from the NPPs to an interim storage facility was calculated during an assumed transportation period. Second, 24 candidate transportation scenarios were constructed by a combination of the decision factors. To construct viable yearly transportation schedules for the selected 24 scenarios, we created a spreadsheet program named TranScenario, which was developed by using MS EXCEL. TranScenario can help schedulers input shipping routes and allocate transportation casks. Also, TranScenario provides information on the cask distribution in the NPPs and in the interim storage facility automatically, by displaying it in real time according to the shipping routes, cask types and cask numbers that the user generates. Once a yearly transportation schedule is established, TranScenario provides some statistical information, such as the voyage time, the availability of the interim storage facility, the number of transported casks sent from the NPPs, and the number of transported casks received at the interim storage facility. By using this information, users can verify and validate a yearly transportation schedule. In this way, the 24 candidate scenarios could be constructed easily. Finally, these 24 scenarios were compared in terms of their operation cost.

Comparison of the transportation risks for the spent fuel in Korea for different transportation scenarios

According to the long term management strategy for spent fuels in Korea, they will be transported from the spent fuel pools in each nuclear power plant to the central interim storage facility (CISF) which is to start operation in 2016. At the start of the operation of the final repository (FR), by the year 2065, transport will then take place between the CISF and the FR. Therefore, we have to determine the safe and economical logistics for the transportation of these spent fuels by considering their transportation risks and costs. In this study, we developed four transportation scenarios for a maritime transportation by considering the type of transportation casks and transport means in order to suggest safe and economical transportation logistics for the spent fuels in Korea. And, we estimated and compared the transportation risks for these four transportation scenarios. Also, we estimated and compared the transportation risks resulting from accidents during the transportation of PWR and PHWR spent fuels by road trailers from the CISF and the FR. From the results of this study, we found that risks resulting from accidents during the transportation of the spent fuels have a very low radiological risk activity with a manageable safety and health consequences. The results of this study can be used as basic data for the development of safe and economical logistics for a transportation of the spent fuels in Korea by considering the transportation costs for the four scenarios which will be needed in the near future.

Neutron measurements around a TN85-type storage cask with high-active waste

Abstract Several types of casks have been deposited in the German interim storage facility for spent fuel assemblies and vitrified high-active waste (HAW) at Gorleben since 1995, most of them of the CASTOR® type. In 2008 a delivery of 11 TN85-type casks arrived. They belong to the Transnuclear/Areva cask family and, compared to the flasks of the German (GNS) CASTOR® type, they differ in the neutron shielding design. Generally, radiation exposure of personnel during transportation and storage of casks containing spent fuel and vitrified waste is caused by mixed photon/neutron fields. Frequently, especially at casks for vitrified waste from reprocessing, neutrons are the major component of radiation exposure. Spectrometric and dosimetric investigations were made around a cask of the TN85-type. Neutron fluence spectra and reference values of the ambient dose equivalent H*(10) were measured by means of a Bonner sphere spectrometer (BSS) at several locations on the cask surface and in its environment. Moreover, commercial area dosemeters, LB6411 neutron monitors and conventional AD 6-type photon dosemeters were used. In addition, the responses of two electronic personal dosemeters for mixed fields (EPD-N2, DMC 2000GN) and a TLD albedo dosemeter were investigated. The neutron spectra obtained from the BSS are presented and compared with former measurements at CASTOR® type casks. The relative responses of the LB6411 survey meter and the individual dosemeters are discussed. The LB6411 monitor indicates H*(10) around the TN85 cask with tolerable measuring uncertainties. The personal dosemeters provide acceptable results for photons but overestimate the neutron dose considerably.

Transport of large nuclear power plant components: experiences in mechanical design assessment

AbstractIn the course of decommissioning of power plants in Germany large nuclear components (steam generator, reactor pressure vessel) must be transported over public traffic routes to interim storage facilities, where they are dismantled or stored temporarily. Since it concerns surface contaminated objects or low specific activity materials, a safety evaluation considering the IAEA transport regulations mainly for industrial packages (type IP-2) is necessary. For these types of industrial packages the requirements from normal transport conditions are to be covered for the mechanical proof. For example, a free drop of the package from a defined height, in dependence of its mass, onto an unyielding target, and a stacking test are required. Since physical drop tests are impossible generally due to the singularity of such 'packages', a calculation has to be performed, preferably by a complex numerical analysis. The assessment of the loads takes place on the basis of local stress distributions, also with con...

Responsible Expansion of Nuclear Power Requires Global Cooperation on Spent-Fuel Management

gating climate change will remain wishful thinking unless some crucial requirements are satisfied. In addition to cost, safety, security, and peaceful use, there will have to be a sustainable solution for managing spent fuel and nuclear wastes—the so-called back end of the nuclear fuel cycle. Highly radioactive spent fuel containing fissile plutonium should not end up in numerous locations scattered around the globe as more and more nations, both large and small, expand or introduce nuclear power. A small number of safely constructed and well-secured storage and disposal facilities must be the goal. The key challenge in this regard is the siting and construction of deep geological repositories for long-lived radioactive wastes. These repositories are expensive; even the smallest state-of-the-art deep facilities for high-level radioactive wastes (HLW) or spent fuel will cost several billion dollars. Even the much admired and most advanced small Finnish repository will cost around $4.5 billion, and cost estimates in the several tens of billions have been published for large programs such as those in the United States and the United Kingdom. Many small nuclear programs or countries starting out in nuclear energy do not have the technical or financial resources to implement a national repository in a timely fashion. They will have to keep their spent fuel in interim storage facilities; this could result in numerous sites all around the world where hazardous materials will be stored for decades to hundreds of years. There must be a better way. One safer and more secure option would be for nuclear-fuel suppliers to take back the spent fuel under a fuel “leasing” arrangement, in which they would pro-

The temporary storage of municipal solid waste – Recommendations for a safe operation of interim storage facilities

Since 1st of June, 2005 it was stipulated that municipal solid waste (MSW) in Germany must be sufficiently pre-treated before final disposal. Thermal and high-performance mechanical-biological processes may be employed for this pre-treatment. Due to the current lack of sufficient operating capacity in the corresponding facilities, part of the waste stream must be held in interim storage until treated or until further utilisation becomes possible. In Germany, the following types of waste with different demands on storage conditions are of concern: These storage solutions have in common that considerable environmental problems can occur as a result of inadequate construction and process engineering. In addition, the temporary storage of waste is also of relevance for the situation of other European countries, which are under pressure to reduce the portion of biodegradable waste going to landfills in order to fulfil the provisions made by European legislation. This article deals with the different approaches for the interim storage of waste, related problems as well as with the demands and possibilities to minimize the environmental risks associated with these solutions.

Safety Analysis of Dual Purpose Metal Cask Subjected to Impulsive Loads due to Aircraft Engine Crash

In Japan, the first Interim Storage Facility of spent nuclear fuel away from reactor site is being planned to start its commercial operation around 2010, in use of dual-purpose metal cask in the northern part of Main Japan Island. Business License Examination for safety design approval has started since March, 2007. To demonstrate the more scientific and rational performance of safety regulation activities on each phase for the first license procedure, CREPEI has executed demonstration tests with full scale casks, such as drop tests onto real targets without impact limiters(1) and seismic tests subjected to strong earthquake motions(2). Moreover, it is important to develop the knowledge for the inherent security of metal casks under extreme mechanical-impact conditions, especially for increasing interest since the terrorist attacks from 11th September 2001(3)-(6). This paper presents dynamic mechanical behavior of the metal cask lid closure system caused by direct aircraft engine crash and describes calculated results (especially, leak tightness based on relative dynamic displacements between metallic seals). Firstly, the local penetration damage of the interim storage facility building by a big passenger aircraft engine crash (diameter 2.7m, length 4.3m, weight 4.4ton, impact velocity 90m/s) has been examined. The reduced velocity is calculated by the local damage formula for concrete structure with its thickness of 70cm. The load vs. time function for this reduced velocity (60m/s) is estimated by the impact analysis using Finite Element code LS-DYNA with the full scale engine model onto a hypothetically rigid target. Secondly, as the most critical scenarios for the metal cask, two impact scenarios (horizontal impact hitting the cask and vertical impact onto the lid metallic seal system) are chosen. To consider the geometry of all bolts for two lids, the gasket reaction forces and the inner pressure of the cask cavity, the detailed three dimensional FEM models are developed and calculated. Main criteria for estimating the maximum leakage rate for the lid metallic seal system are no loss of the pre-stress of the lid bolts, no appearance of the plastic region between the metal seal flanges, and no large relative deformation of the lid seals. Finally, in both cases, the low leakage rate for the metal cask lid closure system under the impulsive loads due to aircraft engine crash will be proved thoroughly.

Construction of long term interim storage facility for nuclear reactor compartments of submarines: German support for utilisation of nuclear submarines in Russia

AbstractAt the world economic summit in Kananaskis, Canada, in June 2002, the G8 heads of state decided on a global partnership against the distribution of nuclear weapons and materials of mass destruction. Based on this framework, the German Federal Ministry of Economics and Technology (BMWi) established a project in October 2003 concerning the storage of decommissioned Russian nuclear submarines. The basis was a German–Russian agreement. On the German side, the project management of this 300 million euro project was assigned to Energiewerke Nord GmbH (EWN) and technical controlling to BAM Bundesanstalt fur Materialforschung und –prufung under respective BMWi contracts. On the Russian side, the Kurchatov Institute has the project management of the long term interim storage facility in Sayda Bay, while the Nerpa shipyard, which is about 25 km away from the storage facility, is dismantling the submarines and preparing the reactor compartments for long term interim storage.The aims of the project — design a...

Seismo-engineering parameters for sites of interim storages for spent nuclear fuel at German nuclear power plants

Within the scope of the licensing procedure for 12 interim storage facilities for spent nuclear fuel at nuclear power plants (NPP) and one for the dismantling of a NPP in Germany, site-specific expert reports were carried out to determine seismo-engineering design parameters. Our work was based on the German nuclear safety standard KTA 2201 part 1 “Design of Nuclear Power Plants against Seismic Events” which requires the derivation of the design earthquake in terms of (macroseismic) intensity. The intensity of the particular design earthquake was evaluated by the deterministic method stipulated in KTA 2201 part 1. According to the current state-of-the-art of science and technology supplementary to the deterministic approach, probabilistic evaluations were done setting a probability of exceedance for the occurrence of the design earthquake of 10 −5 year −1. Geological development and neotectonic conditions of the site surrounding areas were included in the evaluations. For 13 interim storage facility sites, soil-dependent design spectra and corresponding strong-motion duration values were determined. For sites with low seismic hazard site-specific design spectra from the literature were used. In the case of sites with higher seismic hazard (design earthquake⩾VII 1/2 MSK) strong-motion registrations representative for the site were selected from world wide data and subsequently evaluated to derive site-specific design spectra.

SCALE analysis of CLAB decay heat measurements for LWR spent fuel assemblies

A set of decay heat measurements for spent fuel assemblies recently carried out at the Swedish central interim storage facility for spent fuel, CLAB, was analyzed with the SCALE code system. The measurements include a variety of light water reactor assemblies that cover a large burnup range – up to 51 GWd/MTU – and a cooling time domain of interest to spent fuel storage and transportation applications. The results of the analysis show a good agreement between measured and predicted decay heat, with the calculated decay heat in general within the range of the uncertainty of the measured value. The effect of various assembly data on the calculated decay heat is analyzed and discussed. Uncertainties that may arise from various approaches and assumptions in the computational model are identified and examined.

Development of monitoring technique for the confirmation of spent fuel integrity during storage

A method is developed to monitor integrity of spent fuels stored in a canister that is sealed by weld. To achieve the monitoring, Kr-85 gas was newly adopted as a kind of probe. In the case of a fuel rod defect, Kr-85 gas of the fuel rod is leaked in the canister. By detection of gamma ray (514 keV) emitted from Kr-85 outside of the canister, defected rods can be detected without unsealing the canister. The monitoring technique was developed using small-scaled mock-up experiments and simulated calculation. The result showed that Kr-85 gas leakage of about 10 11 Bq is detectable under the noise gamma rays by using the detection system with collimator, which is about 10% of Kr-85 inventory in a fuel rod. Therefore, this monitoring technique is considered as an inspection method prior to transportation of spent fuel from an interim storage facility to a reprocessing plant.

A study on operation time periods of spent fuel interim storage facilities in South Korea

The saturation of South Korea's at-reactor (AR) spent fuel storage pools has created a necessity for additional spent fuel storage capacity. Because the South Korean government has a plan to increase the number of nuclear power plants to 27 units by 2015, the increase of spent nuclear fuel generation will be accelerated. Because there is no clear national plan for spent nuclear fuel permanent disposal, the Korea Hydraulic Nuclear Power Company is planning to construct a spent fuel interim storage facility with 11,000 tHM capacity for Pressure Water Reactor (PWR). This study estimates the operation time periods of interim storage facilities with regard to the re-racking plan of spent fuel storage pools and construction of new nuclear power plants. To do this, the amount of spent fuel generation was estimated through a nuclear power supply plan until the year 2015. After 2015 year, the amount of spent fuel generation was estimated by using three scenarios that this study assumes according to variation of number of nuclear power plants: the “discontinue scenario”, the “maintenance scenario”, and the “increase scenario”. In the case of the “increase scenario”, projections of the share of nuclear power were estimated using the MESSAGE-V method. It is estimated that an interim storage facility will be needed by 2016, and for all scenarios, it is estimated that interim spent storage facilities will be saturated by 2041 with current burnup and by 2049 with extended burnup. In order to get a more meaningful result, it is recommended that a study on the practical storage facility capacity with respect to the risk assessment, public acceptance and further research should follow.

The Sliding and Overturning Analysis of a Free-Standing Cask under Earthquake

A freestanding spent fuel interim storage facility is possible to be selected to house the spent fuel for ChinShan nuclear power station in a period of 5 to 50 years. The design specifications of the storage facility should provide adequate safety assurance under the event of a major earthquake. ANSYS/LS-DYNA computer code is employed in this study to simulate the dynamic behavior of the cask under extremely seismic loading, the criterion which is used to judge whether freestanding cask will slide or overturn is thus established. A cylindrical cask is used as an object which subjected to safety shutdown earthquake of support pad of ChinShan nuclear power station. The cylindrical cask will slide but will not overturn is obtained under maximum earthquake loading.

ICONE15-10405 Development of Borated Aluminum Alloy with Stability at High Temperatures

Some spent fuels generated in nuclear power plants are ongoing plan to be stored in interim storage facilities by metal casks for about 50 years in Japan, until nuclear fuel reprocessing plants can accept these spent fuels. A stainless steel and aluminum alloy containing neutron-absorbing materials is used as a basket that is a component of a partition plate for the spent fuel in the metal cask. We have developed a high-performance borated aluminum alloy. This material has not only high heat conductivity, but also high strength at high temperatures. This strengthening is caused by stable precipitation at high temperatures, created by the addition of boron as a neutron absorber, and of Mn and Cr in the matrix of alloy A6082 to forcibly create the precipitation. The yield strength of the developed alloy is 74 MPa at 523 K and heat conductivity is 185W/m・K. An accelerated test based on the Larson-Miller parameter indicates that this material retains high strength for 50 years at 523 K. The developed alloy is stronger than traditional B-Al specified ASME code case. These results indicate the developed alloy is stable to heat aging and useable for the components of metal casks.