Metal Cask Research Articles

金属キャスク材料(JSME GLF1)の溶接後材料試験

金属キャスク材料(JSME GLF1)の溶接後材料試験

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.

REVIEW AND FUTURE ISSUES ON SPENT NUCLEAR FUEL STORAGE

The safety of metal cask and concrete cask storage technology has been verified by CRIEPI through several research programs on demonstrative testing for the interim storage of spent fuel. The results have been reflected in the safety requirements for dry casks issued by NISA/METI (Nuclear and Industrial Safety Agency, Ministry of Economy, Trade and Industry) of the Japanese government. On top of that, spent fuel integrity has been studied by the Japan Nuclear Energy Safety Organization (JNES). This paper reviews these research programs. Future issues include the long-term integrity of cask components and high burn-up spent fuel.

航空機エンジンの垂直衝突荷重に対する金属キャスクの密封性能評価

To confirm the sealing performance of a metal cask subjected to impact force due to commercial aircraft crash against a spent fuel storage facility, a vertical impact test was carried out. In this test, a simplified deformable missile was used by considering the rigidity of the actual aircraft engine and accelerated to the specified impact velocity (60 m/s) to hit the full-scale lid structure with the primary and secondary lids. Then, the leak rate, the inner pressure between the lids, and the displacement of the lids were measured. The leak rate of the secondary lid exceeded 1.0×10−3 Pa·m3/s upon impact. However, because no residual lid opening displacement occurred after loading, the leak rate recovered to less than 1.0×10−6 Pa·m3/s after 3 h from the impact test. In addition, to clarify the impact behaviour of the lid structure, the impact analysis using the LS-DYNA code was executed. It was found that the lid bolts maintained the good tightening force after impact loading, and the sealing performance of the full-scale metal cask would not be affected immediately by the vertical impact of the aircraft engine with a speed of 60 m/s.

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.

Numerical evaluation of sealing performance of metal cask subjected to aircraft crash

Numerical evaluation of sealing performance of metal cask subjected to aircraft crash

Topics of research and development on concrete cask storage of spent nuclear fuel

This paper addresses topics of research and development (R&D) being challenged for realization of concrete cask storage of spent nuclear fuel in Japan. Comparison between metal cask storage and concrete cask storage is addressed. Background of these R&D and current status of technology on spent fuel storage are described. Need and design concepts of concrete cask storage technology, tests and evaluation of integrity of spent fuel, materials, concrete casks under normal and accident conditions, monitoring technology, etc. are systematically arranged and introduced. Topical problems of these R&D are described.

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.

Preliminary numerical modeling on design of underground facilities for passive pre-cooling of used nuclear fuel by natural ventilation

The authors developed a computer program for predictive calculation of transient underground climate. One can compute simultaneously the variations of flow rates, temperatures and humidities of air flow in the airways along one circuit with time passage, by using the program. They made a one simple circuit model in which heat sources are placed along the drift. The heat sources represent the metal casks in which the used nuclear fuel sticks are put. They approximated a field data set of seasonal cyclic changes of air temperature and humidity at the inlet to the sine curves. Then, they adopted those as the input data. In this paper, the variations of flow rate, temperature and humidity distribution along the model airway with time lapsed since natural ventilation started.

Assessment of integrity of a dual-purpose metal cask after long-term interim storage: seal performance under transport conditions

AbstractSpent fuels generated in nuclear power plants (NPPs) must be stored until they can be reprocessed into new energy sources in Japan. The quantity of spent fuel stored at each NPP site is increasing, and early realisation of a method of interim storage is expected. Dual-purpose metal casks will be used which will not be reopened until they are delivered to a reprocessing plant, in order to minimize radiation exposure to personnel. The Japan Nuclear Energy Safety Organization (JNES) was established on 1 October 2003 with the mission of ensuring public safety from the potential hazards of nuclear energy. JNES have also been conducting a study of dry storage technology for interim storage. The study of verification of metal cask storage technology, the results of which from a storage and subsequent transport safety point of view are presented in this paper, was originally initiated with government funds in 1999 at the Nuclear Power Engineering Corporation, before being transferred to and conducted by J...

Japanese perspectives and research on packaging, transport and storage of spent fuel

The present paper gives an overview of Japanese experimental studies of dual-purpose metal casks. The studies included: cask drop without impact limiters, drop of a heavy weight onto a cask due to building collapse, burial of a cask in debris from building collapse, tipping over of a cask during an earthquake, long-term containment of metal gaskets and transportability of casks after long-term storage. Most of the studies employed full-scale casks for the experiments.

非線形破壊力学による金属キャスクの延性破壊評価手法

非線形破壊力学による金属キャスクの延性破壊評価手法

諸外国における使用済燃料中間貯蔵技術の動向

In the various countries, spent nuclear fuel generated from nuclear power stations will be either "reprocessed", "stored" or "disposed". In any case, it will be "intermediately stored". Therefore, many kinds of storage technologies have been developed and put into practice. In Japan, since it has been determined that "storage facilities away from reactor sites" would be operated by 2010, there has been growing tendency of practical use of storage technology. In this report, taking account of these situations, we investigated trends of spent fuel storage technologies and principal storage technologies that have been developed or put into practical use in the various countries (22 countries), which will be informative for technological development in Japan. The background, process of adoption, and progress of each storage technology (spent fuel storage pool, metal cask, silo, concrete cask and vault) were described. Besides, we classified those storage facilities in various countries from three points of view (location, storage form and safety function), and showed future direction of these storage technologies. Moreover, we mentioned the applicability of these storage technologies of the various countries to Japan.

INHIBITION OF GROWTH OF MICRO-ORGANISMS BY OXYGEN

During laboratory experiments on the effect of different gaseous atmospheres on the microflora of unpasteurized beer in metal casks, some anomalous results appeared when using pure oxygen. Investigation shows that oxygen tension at a sufficiently high level can inhibit and restrict the growth of a large number of micro-organisms capable of occurring in beer, and this effect is due to the oxygen and not to the pressure.

TIMBERS USED BY BREWERS

The essentials in timbers for vats and casks include impermeability to liquids, resistance to fungal attack, freedom from taint and minimal change in size on wetting and drying; of these, Impermeability is of outstanding importance, and reaches a high level in the white oaks. European and American sources of oak have recently been supplemented by supplies from Persia, though some samples from this source have proved unsound and cases have been known of beer-tainting following the growth of Stereum subpileatum; steam treatment of heads and staves should remove danger from this fungus. Laminated casks would probably be satisfactory if the laminations were thick enough; metal casks have advantages and disadvantages, as have also metal-lined wooden casks. In timbers of building construction, every precaution should be taken against favouring the development of dry-rot. Effective treatments are now available to combat wood-boring insects.