The relevance of IAEA tests to severe accidents in nuclear fuel cycle transport

Abstract

The design and performance standards for packages used for the transport of nuclear fuel cycle materials are defined in the IAEA Regulations for the Safe Transport of Radioactive Materials, TS-R-1, in order to ensure safety under both normal and accident conditions of transport. The underlying philosophy is that safety is vested principally in the package and the design and performance criteria are related to the potential hazard. Type B packages are high-duty packages which are used for the transport of the more radioactive materials, notably spent fuel and vitrified high-level waste (VHLW). Tests are specified in the IAEA regulations to ensure the integrity of these packages in potential transport accidents involving impacts, fires or immersion in water. The mechanical tests for Type B packages include drop tests onto an unyielding surface without giving rise to a significant release of radioactivity. The objects which could impact upon a package in real-life transport accidents, such as concrete roads, bridge abutments and piers, will yield to some extent and absorb some of the energy of the moving package. Impact tests onto an unyielding surface are therefore relevant to impacts onto real-life objects at much higher speeds. The thermal test specifies that Type B packages must be able to withstand a fully engulfing fire of 800°C for 30 min without significant release of radioactivity, and this has to be demonstrated, for example, by analytical studies backed up by experimental tests. The regulations also specify immersion tests for Type B packages of 15 m for 8 h without significant release of radioactivity; and in addition for spent fuel and VHLW packages, 200 m for 1 h without rupture of the containment. There is a large body of evidence to show that the current IAEA Type B test requirements are severe and cover all the situations which can be realistically envisaged in the transport of spent fuel, VHLW and other fuel cycle materials. Any proposals for more severe tests, which have little technical justification, should therefore be treated with caution since this could result in a loss of public confidence in the current regulations, and the ratcheting up of design requirements which could not be justified on quantitative safety grounds.     

Limiting Activities and Activity Concentrations in the Transport of Radioactive Materials

Abstract

The activity limits for Type A packages are determined by a set of criteria and hypothetical exposure scenarios known as the Q system. This system was first used to calculate activity limits for Type A packages for inclusion in the 19.85 IAEA regulations and the methodology has been described in the explanatory material for the regulations, IAEA Safety Series No 7. The new IAEA Basic Safety Standards incorporate revised dose coefficients for intakes of radionuclides. For the latest IAEA Transport Regulations, the Q system has been updated to take into account these more recent dosimetric data, and more comprehensive nuclear data. The updated Q system is described and some of the consequent changes in activity limits for Type A packages are illustrated. Member States of the European Union are subject to a Basic Safety Standards Directive, which contains radionuclide specific Exemption Values. The derivation of these values together With their application to transport is discussed.     

Penetration behavior of water solution containing radioactive species into dried concrete/mortar and epoxy resin materials

Penetration behavior of radionuclides such as ¹³⁷Cs into dried concrete material, dried mortar material and epoxy paint for a few dozen days was observed using a solution containing fission products extracted from irradiated fuels to obtain fundamental information on the radionuclide penetration rate and depth. Hardly any radionuclides could penetrate into the epoxy paint. The radionuclide solution penetrated into concrete and mortar materials to a depth of a few millimeters for a few dozen days. The penetration behavior observed near the surface of concrete and mortar materials was similar to the diffusion of nuclides in media such as water-saturated concrete, bentonite and cement materials.     

Behaviour of a Package Dropped Onto Yielding and Unyielding Targets

Abstract

IAEA transport regulations require the 9 m drop test for type B packages. The target used in this drop test must be unyielding. However, the real target that a transport package might encounter at an accident during transport is a yielding target, such as concrete, asphalt, or soil. To compare the impact acceleration between a real target and an unyielding target, analyses of the drop test onto a real target and an unyielding target were performed by using a LS-DYNA-3D computer code. A road surface is usually concrete or asphalt, and such surfaces are very hard; but there are soil, sand, etc. under these materials, so the impact caused by a drop accident is relatively small. It becomes clear that the drop height onto a road, corresponding to the 9 m drop height required by IAEA regulations is about 50 m, and the impact velocity is about 110 km.s^?1     

Demonstration of structural performance of IP-2 packages by advanced analytical simulation and full-scale drop test

Two new types of IP-2 (Industrial Package Type 2) to transport low and intermediate level radioactive waste (LILW) steel drums from nuclear power plants to a disposal facility have been developed in accordance with the IAEA and Korean regulations for radioactive materials. According to the regulations, both packages must preserve their structural performance after they are subjected to 0.9 m free drop tests, which are prescribed as normal conditions.In this study, an advanced analytical simulation and an evaluation process using the finite element (FE) method have been developed for the design assessment of the newly developed IP-2s. Then, analytical simulations for the various drop orientations were performed to evaluate the structural performance of the packages and demonstrate their compliance with the regulatory requirements. Also, full-scale drop tests were carried out to verify the numerical tools and modeling methodology used in the analyses and to confirm the performance of the IP-2s. In addition, parametric studies are carried out to investigate the sensitivity of the analytical variables, such as the material model and modeling methodology.In addition, this paper intends to provide basic guidance on the analytical simulation and evaluation process specifically for Korean types of transport packages, because numerous transport packages must now be developed for the various kinds of LILW that have accumulated in temporary storage facilities in Korea.     

Computer Modelling of the Impact Performance of Containers for the Transport of Radioactive Materials

Abstract

ABA Technology is an acknowledged world expert in the structural dynamics area through its research programmes in support of nuclear power. Initially, the impact and blast response of metal and reinforced concrete structures relevant to nuclear power plants were studied. Since the mid 1980s these studies have been expanded to include containers for transporting radioactive materials. These programmes are continuing and new areas of interest are being addressed. Experimental transport performance studies are conducted using large gas guns and drop test facilities to achieve impact velocities at, and above, regulatory conditions. Instrumentation allows monitoring of transient pressures, accelerations, displacements, strains and loads. The data are used to predict full-scale structural response from scale models, and to verify calculation methods which range from PC-based mechanistic models to non-linear finite element codes on AEA Technology's CRAY-2 computer. Emphasis is placed on verifying procedures to predict margins to failure in containers. For many structures this involves identifying appropriate failure criteria and the requirement for including strain rate effects. Where necessary special developments of computer codes are made. To date three types of container have been studied: a cylindrical flask for spent fuel, and waste packages consisting of a ruggedised ISO container and a steel clad concrete container. The combination of experimental testing and analysis provides an optimum solution for design and assessment problems and the proven techniques are being transferred to many other applications in other industries.     

The First 40 FT Freight Container in Europe Qualified as an IP-2/IP-3 and Type a Package

Abstract

The first successful free fall drop test with a 40 ft ISO freight container in Europe (as far as we know also in the world) took place in Bremen (Germany) at the dry dock of the former Vulkan ship yard on 25 September 1998. This drop test was performed to qualify the ISO Boxcontainer as an IP-2/IP-3 and Type A package in accordance with IAEA Regulations Safety Series No 6 (1985 edition, as amended 1990) and the new IAEA Safety Standards Series No ST-1 (1996 Edition). The freight container has successfully passed the whole sequence of required tests to demonstrate compliance with Type A requirements (free drop test, stacking test, penetration test and, instead of the water spray test, the more stringent pressure and bubble test was performed) of the IAEA Regulations. This paper concentrates on the free fall drop test because this is the most difficult of the required Type A tests which needs to be passed. Further, the free fall drop test is required to qualify a freight container in accordance with the alternative requirements for industrial packages IP-2,3 (new ST-1, § 627), the requirements for industrial packages (new and old IAEA Regulations) and Type A requirements. Therefore, the freight container was qualified as IP-2,3 and Type A package performing a free fall drop test. The overall dimensions of the so called LONGFORCE® container are: length 12192 mm (40 ft); width 2438 mm (8 ft); height 2491 mm (8 ft 6 in). The 40 ft ISO freight container prototype was fully loaded with 28 t of steel plates together with shock absorbing material to simulate the load and load securing system. The total drop test weight was 35·6 t. In accordance with IAEA Regulations Safety Series No 6 and ST-1, the LONGFORCE® container was dropped onto an unyielding foundation in a position which suffered the maximum damage in respect of the package safety features. The package was dropped on its corner, door side down on the roof, with the centre of gravity over the impact area (slap-down drop). The container was lifted 12·6 m high (highest point) respectively 0·3 m (lowest point) under a drop angle of 70°. The combined mass of the concrete block and the steel plate (impact pad) was way above 100 times that of the container test specimen. The first impact resulted in an acceleration of about 100 g where the maximum was near the impact. The second impact, in general, yielded far higher acceleration values in the vertical direction of 160 up to 200 g. A third impact was recorded which turned out to be decisive, showing maximum acceleration readings in the range of about 200 up to 250 g. The container was inspected after the drop test and deformations of the container rear corner castings (area second impact) and a small weld crack in one of the corner castings welds was found. On the container floor one third of transverse support beams showed Sform distortion. The LONGFORCE container was leak tested prior to and after the drop test in compliance with the STM (STM stands for Safety Technology Management GmbH, owner of the container design and rights and sponsor of the drop test work) leak test procedure. The leak tests consisted of filling the container with pressurised air up to 5 kPa and recording a possible pressure drop over a determined test period. The container was considered leak tight prior to and after the drop test based on the permissible limits set in the leak test procedure. The free fall drop test is considered a full success qualifying the 40 ft LONGFORCE container as an IP-2/IP-3 Type A package in compliance with the IAEA SS No 6 and also with the new IAEA ST-1 regulations.     

Rice husk ash (RHA) as cement admixture for immobilization of liquid radioactive waste at different temperatures

Cementitious materials will initially act as a mechanical barrier preventing activated water flow through the waste for a long time, and thus will contribute to the retardation of dissolved radionuclides by the combination of physical and chemical interactions. Most chemical species in aqueous solutions will undergo some kind of (chemical) interactions with any solids of the cementations material. Therefore, it is of great importance to develop a quantitative understanding of the chemical processes involved and to strictly differentiate between physical and chemical aspects of radionuclide transport through such materials. A study is undertaken to determine the waste immobilization performance of (Cs⁺) wastes in cement-RHA mixtures. In addition to evaluating the effects of RHA on the leaching properties of cemented waste forms, the effect of addition of (RHA) on the strength of the cemented waste form is also investigated. However, RHA addition of 30% causes a significant increase in the hydraulic stability of cemented waste form. RHA enhances the strength; leaching and durability of cement may be through three primary actions which are the filler effect, the acceleration of ordinary Portland cement hydration and the pozzolanic reaction with calcium hydroxide (CH). The results were compared to control sample, and the viability of the RHA addition to concrete was verified. The use of these minerals results in ecological, economic and energy saving considerations.     

Transport of radioactive materials: the need for radiation protection programmes

Abstract

The increase in the use of radioactive materials worldwide requires that these materials be moved from production sites to the end user, or in the case of radioactive waste, from the waste generator to the repository. Tens of millions of packages containing radioactive material are consigned for transport each year throughout the world. The amount of radioactive material in these packages varies from negligible quantities in shipments of consumer products to very large quantities in shipments of irradiated nuclear fuel. Transport is the main way in which the radioactive materials being moved get into the public domain. The public is generally unaware of the lurking danger when transporting these hazardous goods. Thus radiation protection programmes are important to assure the public of the certainty of their safety during conveyance of these materials. Radioactive material is transported by land (road and rail), inland waterways, sea/ocean and air. These modes of transport are regulated by international 'modal' regulations. The international community has formulated controls to reduce the number of accidents and mitigate their consequences should they happen. When accidents involving the transport of radioactive material occur, it could result in injury, loss of life and pollution of the environment. In order to ensure the safety of people, property and the environment, national and international transport regulations have been developed. The appropriate authorities in each state utilise them to control the transport of radioactive material. Stringent measures are required in these regulations to ensure adequate containment, shielding and the prevention of criticality in all spheres of transport, i.e.routine, minor incidents and accident conditions. Despite the extensive application of these stringent safety controls, transport accidents involving packages containing radioactive material have occurred and will continue to occur. When a transport accident occurs, it is unlikely to result in a significant release of radioactive material, loss of shielding or loss of criticality control.     

Qualifying a 40 ft ISO Freight Container as a Type IP-2, IP-3 Package by Performing a Full Scale Drop Test

Abstract

The first successful worldwide free fall drop test with a 40 ft ISO freight container took place in Bremen (Germany) at the dry dock of the former Vulkan shipyard on 25 September 1998. This drop test had to be performed to qualify the ISO Boxcontainer as a Type IP-2, IP-3 package in accordance with the new IAEA Safety Standards Series No ST-1 (1996 Edition). Dynamic impact requirements will become mandatory for freight containers to be qualified as Type IP-2,3 packages in compliance with IAEA ST-1 paragraph §627 ‘Alternative Requirements for IP-2,3 Packages’ (comes into force in January 2001). STM has fulfilled the dynamic impact requirements in performing a full scale drop test. The 40 ft ISO freight container prototype (L × W × H = 12192mm × 2438 mm × 2491 mm) was fully loaded with 28 t of steel plates together with shock absorbing material to simulate the load and load securing system. The total drop test weight was 35.6 t. In accordance with the new IAEA Safety Standards Series No ST-1 requirements, the so-called LONGFORCE® container was dropped onto an unyielding foundation in a position which produced the maximum damage in respect of the package safety features. The package was dropped on its comer, door side down on the roof, with the centre of gravity over the impact area (slap-down drop). The container was lifted 12.6 m high (highest point) and 0.3 m (lowest point) under a drop angle of 70°. The combined mass of the concrete block and the steel plate was more than 100 times that of the container test specimen. The first impact resulted in an acceleration of about loog where the maximum was just before the impact. The second impact, however, turned out to be decisive showing maximum acceleration readings in the range of 250g. The container has been inspected after the drop test and deformations of the container rear comer castings (area of second impact) and a small weld crack in one of the comer casting welds was found. On the container floor one third of transverse profiles showed S-form distortion. The LONGFORCE container was leak tested prior to and after the drop test in compliance with the STM leak test procedure. The leak tests consisted of filling the container with pressurised air up to 5 kPa and recording a possible pressure drop over a determined test period. The container was considered leak tight prior to and after the drop test based on the permissible limits set in the leak lest procedure. The free fall drop test is considered a full success qualifying the 40 ft LONGFORCE container as Type IP-2, Ip-3 package in compliance with the new IAEA Safety Standards Series No ST-1 requirements.     

Drop test program with half scale model CASTOR® HAW/TB2

Abstract

Federal Institute for Materials Research and Testing (BAM) is the competent authority for mechanical and thermal safety assessment of transport packages for spent fuel and high level waste in Germany. In context with package design approval of the new German high level waste cask CASTOR® HAW28M, BAM performed several drop tests with a half scale model of the CASTOR® HAW/TB2. The cask is manufactured by Gesellschaft für Nuklear Service mbH and was tested under accident transport conditions on the 200 tons BAM drop test facility at the BAM Test Site Technical Safety. For this comprehensive test program, the test specimen CASTOR® HAW/TB2 was instrumented at 21 measurement planes with altogether 23 piezo resistive accelerometers, five temperature sensors and 131 triaxial strain gauges in the container interior and exterior respectively. The strains of four representative lid bolts were recorded by four uniaxial strain gauges per each bolt. Helium leakage rate measurements were performed before and after each test in the above noted testing sequence. The paper presents some experimental results of the half scale CASTOR® HAW/TB2 prototype (14?500 kg) and measurement data logging. It illustrates the extensive instrumentation and analyses that are used by BAM for evaluating the cask performance to the mechanical tests required by regulations. Although some of the quantitative deceleration, velocity and strain values cannot be shown because of confidentially issues, they are provided qualitatively to illustrate the types of measurements and methodologies used at BAM.     

Waste Package and Shipment Aspects in Relation to Transport and Disposal Requirements

Abstract

In the management of radioactive waste, different processes have to be considered such as conditioning, interim storage and final disposal together with transport as the linking process. Attention should be paid to all the relevant steps within these processes, in particular to derive appropriate waste package requirements for a safe waste management system as well as to obtain a consistent regulatory framework. Radioactive waste arising from research and development centres, nuclear power plant operation, decommissioning, the nuclear fuel cycle industry, and applications of radioisotopes in medicine, industry and research, has finally to be shipped to a final disposal site. Therefore waste packages are subject to both the regulatory requirements of transport and the requirements of disposal. Resulting consequences for waste package limitations will be discussed, in particular for low and intermediate level waste taking into account LSA/SCO regulations for transport and waste acceptance criteria for disposal in Germany. Some aspects of different package concepts, like the use of non-reusable or reusable packages, will be considered as well as the application of LSAISCO regulations and further development of LSA/SCO criteria.     

A summary of recent package testing activities at Oak Ridge National Laboratory

Abstract

The history of testing of radioactive material packages at Oak Ridge National Laboratory (ORNL) dates back to the early 1960s, and includes the testing of hundreds of different packages of all shapes and sizes. This paper provides an overview of ORNL's new Packaging Research Facility at the National Transportation Research Center (NTRC), and describes recent package testing successes conducted at the NTRC from September 2002 to September 2003. This paper also provides an overview of the package testing capabilities available at NTRC. Between 2002 and 2003, ORNL conducted tests on the following packages: rackable can storage box (RCSB); ES-2100; DT-20; DPP-2; BRM shielded overpack; Fernald Silos IP-2 waste package; and RAJ II BWR fresh fuel package. Tests of the RCSB, a storage package for highly enriched uranium, involved two test specimens, dropped from 28 ft(8.4 m) in different orientations. The ES-2100 and DPP-2 involved four and six test units, respectively, subjected to the entire Type B normal conditions of transport and hypothetical accident conditions testing sequence, including thermal tests. A single DT-20 package was subjected to a subset of the Type B tests to confirm package performance. The BRM shielded overpack, weighing about 500 kg, was subject to the Type A package tests. Three Fernald Silos waste package test units — a large package weighing about 10,000 kg for shipping grouted waste removed from the Fernald site — were subjected to IP-2 tests. And finally, two RAJ II boiling water reactor fresh fuel test units were subjected to Type B 9 m drop and 1 m puncture tests.     

Modelling of radioactive material release from waste packages in case of a fire event

Assumed incidents in the operational phase of the planned German repository Konrad for radioactive waste with negligible heat production were investigated in order to assess their possible radiological consequences. Release fractions of the radioactive substances contained in waste packages were assessed from experimental data obtained under thermal impact. They are given for halogens, tritium, ‘4C and other radionuclides and are classified according to the waste form groups and waste container classes.     

Test Facilities for Radioactive Material Transport Packages (Ontario Hydro,Canada)

Abstract

The Ontario Hydro test facilities for Type A and Type B packages for the transport of radioactive materials are described.     

Test Facilities for Radioactive Material Transport Packages (Australia)

Abstract

Test facilities at the Australian Nuclear Science and Technology Organisation, for Type A and Type B packages for the transport of radioactive materials are very briefly described.     

Qualification Tests for a Type B(U) Package

Abstract

The primary objective for the safety of radioactive materials transport is to protect human health and the environment taking into consideration its potential risks and radiological consequences. Romania as a Member State of the International Atomic Energy Agency hasimplemented national regulations for the safe transport of radioactive materials in accordance with the Agency's recommendations as well as other international specialisedorganisations. The paper will describe the qualification tests performed for a Type B(U) package, intended to be used for the transport of the radioactive sources ²⁴¹Am and ¹³⁷Cs. For this kind of package the tests were performed for the first time inRomania and include: the water spray test, the 1.2 m free drop test, the stacking test, the penetration test, the 9 m free drop test, the thermal test and the submersion under a head of water of at least 15 m. The test facilities used for performing qualification tests for the Type B(U) package as well as experience and conclusions will be also presented.     

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

Abstract

In 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 consideration of radiation induced brittleness of the material and with consideration of recent scientific investigation results. Large nuclear components have typically been transported in an unpackaged manner, so that the external shell of the component provides the packaging wall. The investigation must consider the entire component including all penetration areas such as manholes or nozzles. According to the present IAEA regulations the drop position is to be examined, which causes the maximum damage to the package. In the case of a transport under special arrangement a drop only in an attitude representing the usual handling position (administratively controlled) is necessary. If dose rate values of the package are higher than maximum allowable values for a public transport, then it is necessary that additional shielding construction units are attached to the large component.     

Test Facilities For Radioactive Materials Transport Packages (Criepi,Japan)

Abstract

Facilities at the Central Research Institute of the Electric Power Institute, Japan, for testing Type A and Type B packages for the transport of radioactive materials, are described.     

The Swiss Concept—Container Design and the Transport of L/ILW to the Planned Final Repository

Abstract

The design of the Swiss final repository for short lived L/ILW is based on a Nagra container and package concept. The package handling operations have been restricted to a minimum through the design of special handling tools. e.g. a gripper for 9 drums. The routine transport weight by rail is 56 t, and for non-routine transport 80 t (maximum). The transport of drums and reprocessing waste will be in re-usable steel containers and that of decommissioning waste in dual purpose transport and disposal containers. Most of the containers have standardised dimensions and corner fittings which are based on the ISO dimensions. The modes of transport for the containers and packages within the repository include overhead cranes, an air cushion platform for precise manoeuvering in limited spaces and internal rail transport. The handling and transport will mostly be remotely controlled and monitored by video cameras from the control room. Hence, the exposure times of the operating personnel in the radiation environment is minimised.