Sei-Hun Yun

ITER storage and delivery system R&D in Korea

Korea is supposed to develop the ITER tritium storage and delivery system (SDS), which is one of the main components of the ITER tritium plant. For successful procurement, there are several ongoing R&D activities in the detailed design phase. Investigation of design parameters of the storage and delivery beds has been performed. Small and large-scale mock-ups of ZrCo beds are used to test the capability of desirable rapid delivery and recovery performance and to establish the pertinent procedure of in-bed calorimetry. An experimental apparatus is prepared to develop the integration and verification technologies for the unit processes of the tritium SDS. The performance test of a tritium-compatible metal bellows pump is examined, and the results show a reasonable agreement with the catalog data of the pump. A tritium storage and delivery bed simulator has been developed to simulate various bed operation scenarios under normal and abnormal conditions. A prototype of the SDS simulator is fabricated, and the bed operation scenario generation program to be applied to this simulator is developed. The design requirement of the tritium loading station (TLS) calorimeter is prepared based on a benchmarking mock-up calorimeter, namely, Korea Electric Power Research Institute Tritium Laboratory (KEPTL) calorimeter. Documents for the procurement of the TLS calorimeter will be developed through the experience on the KEPTL calorimeter operation.

R&D Activities on the Tritium Storage and Delivery System in Korea

Abstract R&D activities on the tritium storage and delivery system include the development of getter beds to increase tritium recovery and delivery performance, the investigation of tritium reaction characteristics with ZrCo metal-hydride, in-bed calorimetry as tritium measurement techniques, and the development of process design technologies for the storage and delivery system such as pump performance test and bed simulator. The current status of the R&D activities on these subjects is addressed in this paper.

INITIAL TEST RESULTS OF A FAST HEAT TRANSFER RESPONSE ZrCo HYDRIDE BED

Abstract We are developing an innovative ZrCo hydride bed design, which is characterized by a large cylindrical filter, very thin cylindrical metal hydride powder packed layer, and large relative heating area per unit weight of ZrCo powder for ITER fuel cycle application. To validate this design concept, two ZrCo bed models each loaded with 127 g of ZrCo were tested by using H2 gas. In the first model, ZrCo powder was packed into the 3 mm gap between the filter cylinder and the vessel, and mold heater elements were attached to the outer surface of the vessel. The second model consisted of a layer of ZrCo powder packing (7 mm thickness), coiled cable heaters attached independently to the outer surface of the primary vessel and the inner surface of the filter cylinder. This paper presents detailed design features of the ZrCo bed models, and test results of the beds performances, i.e., temperature transient of the ZrCo packed bed during fast heating, hydriding rate up to 90-99% recovery, and 90-98% delivery fraction.

Safety Analysis of a Hydrogen Isotopes Process

A nuclear fusion fuel cycle plant is composed of various subsystems such as a hydrogen isotope storage and delivery system, a tokamak exhaust processing system, and a hydrogen isotope separation system. Korea shares in the construction of the International Thermonuclear Experimental Reactor fuel cycle plant with the EU, Japan and US, and is responsible for the development and supply of the storage and delivery system. We thus present details on the hydrogen isotope process safety. The main safety analysis procedure is to use a hazard and operability study. Nine segments were studied how the plant might deviate from its design purpose. We present a detailed description of the process, examine every part of it to determine how deviations from the design intent can occur and decide whether these deviations can give rise to hazards. We determine possible causes and note protective systems, evaluate the consequences of the deviation, and recommend actions to achieve our safety goal.

A Study of the Consecutive Absorption/Desorption Cycles of ZrCo–H 2 System

Consecutive absorption/desorption cycles of the ZrCo-H2 system were studied to simulate the real International Thermonuclear Experimental Reactor (ITER) hydrogen getter system. A ZrCo getter was used in this paper instead of the depleted uranium (DU) getter material, which has been recently considered as the hydrogen getter in ITER. In a cyclic pressure-composition isotherm (PCI) measurement, the high-pressure Sievert apparatus seems impractical to describe the equilibrium state of the ZrCo-H2 system in detail, especially for the desorption stage. This high-pressure PCI apparatus, however, shows cause and effect well, from the previous getter state to the following state in presenting hydriding/dehydriding performance. In case of the ZrCo-H2 system or in case of the DU-H2 system having multiple getter bed battery, a similar affection by previous getter status might be related and a similar aspect could be shown to consider further ITER design; for example, a need for control logic from PCI measurements using a high-pressure Sievert apparatus.

Hydriding Performances and Modeling of a Small-Scale ZrCo Bed

Abstract Korea has been developing nuclear fusion fuel storage and delivery system (SDS) technologies including a basic scientific study on hydrogen storage. To develop nuclear fusion technology, it will be necessary to store and supply hydrogen isotopes needed for Tokamak operation. SDS is used for storing hydrogen isotopes as a metal hydride form. We designed and fabricated a small-scale getter bed of zirconium cobalt (ZrCo). The rapid hydriding of tritium is very important not only for safety reasons but also for the economic design and operation of the SDS. The effect of the initial absorption temperatures on the hydriding of ZrCo was measured and analyzed. The experimental results of the hydrogen pressure of hydriding (ZrCoH2.8) at various cooling temperatures are in agreement with the calculated values using numerical modeling equations. The effect of a helium blanket on hydriding was measured and analyzed. The experimental results of the hydriding with 0 %, 4%, and 8% of helium concentration are in agreement with the calculated values based on numerical modeling equations.

Key technologies for tritium storage bed development

Abstract ITER Storage and delivery system (SDS) is a complex assembly system. Lots of individual components including tens of storage beds, a few reactors, multiple transfer pumps, vessels, umpteen instruments & sensors which are interconnected with tubing and fittings in a confined glovebox system are to be installed in the given Tritium Plant area. The most important SDS getter bed will be utilized for absorbing and desorbing of hydrogen isotopes in accordance with the fusion fuel cycle scenario. This paper deals with R&D activities on SDS bed design, especially thermal hydraulic analysis in heat loss aspect, the real-time gas analysis in He-3 collection system, and introductory experimental plans using depleted uranium (DU) getter material for storage of hydrogen isotopes, especially of tritium.

ESTIMATION OF THERMOPHYSICAL PROPERTIES IN MASSIVE ZrCoHx SYSTEM

Abstract Thermophysical properties of the complex metal hydride system such as zirconium cobalt hydride, an intermetallic hydride compound, in a massive state were estimated by introducing a crystal lattice structure in a stepwise formation and applying a mixing rule for each property. Experimental data in rarity in metal hydride system was used to calculate and to correlate the consistency of the mixed thermal and physical properties of the complex atomic structure in a unit cell. As a result, the volume expansion of the ZrCoHx was greatly influenced by the hydrogen content and increased to a maximum range of 36% at ZrCoH3 system, but no meaning in the thermal expansion in engineering concept. In consideration of the heat capacity the temperature effect due to the hydrogen—an interstitial heat quantity—in the metal complex formation was mainly attributed, but not much for the hydrogen content (H/ZrCo ratio). In the temperature range between 200K and 600K the heat capacity of hydrogen atom was taken into account to reveal a sharp discrepancy in its non-hydriding property, especially in the lower temperature range. Atomic hydrogen was expected to behave from a gas to a solid property in heat capacity in the temperature ranges from 600K to 200K.

Hydrogen Brittleness on Welding Part for SDS Bottles

Abstract >> Tritium was attracted with high energy source in neutron fusion energy systems. A number of researchwas performed in tritium storage materials. The Korea was raised storage and delivery systems (SDS) of internationalthermonuclear experimental reactor (ITER) research. However, bottles of SDS would be important because of stability. The bottles have a welding zone, this zone will be vulnerable to hydrogen embrittlement. This zone havea high thermodynamic energy and heat deterioration. Therefore bottles were studied about hydrogen embrittlementto retain stability. The heat treatment of hydrogen was carried under pressure-composition-temperature (PCT) apparatus because of checking at real time. And then, mechanical properties were evaluated by tensile test andhardness test. In results of this study, hydrogen atmosphere condition is very important by tensile test and kineticstest. The samples were evaluated, that is more weak hydrogen pressure, increasing temperature and time. This results could be useful in SDS bottle designs.Key words : Hydrogen embrittlement(수소 취성 ), Hydrogenation(수소화), Tensile test(인장 시험 ), Hardness(경도),Tritium storage(삼중수소저장), SDS(저장 및 공급)

Rapid Cooling Performance Evaluation of a ZrCo bed for a Hydrogen Isotope Storage

Abstract >> The nuclear fuel cycle plant is composed of various subsystems such as a fuel storage and deliverysystem (SDS), a tokamak exhaust processing system, a hydrogen isotope separation system, and a tritium plantanalytical system. Korea is sharing in the construction of the International Thermonuclear Experimental Reactor(ITER) fuel cycle plant with the EU, Japan ,and the US, and is responsible for the development and supply ofthe SDS. Hydrogen isotopes are the main fuel for nuclear fusion reactors. Metal hydrides offer a safe and convenientmethod for hydrogen isotope storage. The storage of hydrogen isotopes is carried out by absorption and desorptionin a metal hydride bed. These reactions require heat removal and supply respectively. Accordingly, the rapid storageand delivery of hydrogen isotopes are enabled by a rapid cooling and heating of the metal hydride bed. In thisstudy, we designed and manufactured a vertical-type hydrogen isotope storage bed, which is used to enhance the cooling performance. We present the experimental details of the cooling performances of the bed using variouscooling parameters. We also present the modeling results to estimate the heat transport phenomena. We comparedthe cooling performance of the bed by testing different cooling modes, such as an isolation mode, a natural convection mode, and an outer jacket helium circulation mode. We found that helium circulation mode is the mosteffective which was confirmed in our model calculations. Thus we can expect a more efficient bed design byemploying a forced helium circulation method for new beds.Key words : Nuclear fusion energy(핵융합), Storage and delivery bed(수소저장용기), Hydrogen isotope(수소동위원소), Metal hydride(금속수소화물), Zirconium cobalt(지르코늄 코발트)