Differential pressure rise event for filters of HTTR primary helium gas circulators, 1; Investigation of differential pressure rise event

Nemoto, Takahiro; Arakawa, Ryoki; Kawakami, Satoru; Nagasumi, Satoru; Yokoyama, Keisuke; Watanabe, Masashi; Onishi, Takashi; Kawamoto, Taiki; Furusawa, Takayuki; Inoi, Hiroyuki; et al.

JAEA-Technology 2023-005, 33 Pages, 2023/05

JAEA-Technology-2023-005.pdf:5.25MB

During shut down of the HTTR (High Temperature engineering Test Reactor) RS-14 cycle, an increasing trend of filter differential pressure for the helium gas circulator was observed. In order to investigate this phenomenon, the blower of the primary helium purification system was disassembled and inspected. As a result, it is clear that the silicon oil mist entered into the primary coolant due to the deterioration of the charcoal filter performance. The replacement and further investigation of the filter are planning to prevent the reoccurrence of the same phenomenon in the future.

Thick target neutron yields from 100- and 230-MeV/nucleon helium ions bombarding water, PMMA, and iron

Tsai, P.-E.; Heilbronn, L. H.*; Lai, B.-L.*; Iwata, Yoshiyuki*; Murakami, Takeshi*; Sheu, R.-J.*

Nuclear Instruments and Methods in Physics Research B, 449, p.62 - 70, 2019/06

https://doi.org/10.1016/j.nimb.2019.04.030

The secondary neutrons produced from 100- and 230-MeV/nucleon He ions, respectively, stopping in the thick iron, PMMA and water targets are measured by the time of flight method combined with the pulse shape discrimination of liquid scintillators. The experimental data show that the secondary neutrons were contributed from breakup of projectiles, emission from overlap regions of projectile nuclei and target nuclei, and evaporation of projectiles and target nuclei. The measured double-differential thick target neutron yields, angular distributions, and total neutron yields per ion, were benchmarked by the PHITS, FLUKA, and MCNP model calculations. The default models in these codes agree the experimental data well at intermediate-to-large angles in the low-to-intermediate energy range. However, the physics models implemented in PHITS need further improvement for some particular nuclear interaction mechanisms, and this work can be an importance reference for future model development.

An Evaluation of the long-term stagnancy of porewater in the neogene sedimentary rocks in northern Japan

Nakata, Kotaro*; Hasegawa, Takuma*; Oyama, Takahiro*; Ishii, Eiichi; Miyakawa, Kazuya; Sasamoto, Hiroshi

Geofluids, 2018, p.7823195_1 - 7823195_21, 2018/01

https://doi.org/10.1155/2018/7823195

A groundwater scenario is one of the scenario for safety assessment of geological disposal of high-level radioactive waste. In the safety assessment for groundwater scenario, the slow groundwater flow for a long-term should be an important factor. In the present study, study on stability of groundwater in the Koetoi and Wakkanai formations of Neogene marine based sedimentary rock at the Horonobe area, Hokkaido was performed by investigating the isotopes of chlorine and helium, and the stable isotopes of water. As the results, the stability of groundwater in deeper part of the Wakkanai formation was suggested due to no direct evidence of meteoric water intrusion during the uplift since ca. 1 Ma. Contrary, the groundwater both in the Koetoi formation and the upper Wakkanai formation would be unstable because the meteoric water intrusion was suggested by paleohydrogeological condition and the results of groundwater dating. Likely the Horonobe area, the accurate dating of groundwater would be difficult due to the complex effects of upward and mixing water derived from diagenesis in the thick sediment formation. However, a comparative procedure using both the results of groundwater dating and paleohydrogeological information would be useful for general evaluation of groundwater flow conditions for the long-term (i.e., check the possibility for long-term stability of groundwater).

Development of active control technology for impurities in coolant helium using High Temperature Engineering Test Reactor (HTTR)

Hamamoto, Shimpei; Nemoto, Takahiro; Sekita, Kenji; Saito, Kenji

JAEA-Technology 2015-048, 62 Pages, 2016/03

JAEA-Technology-2015-048.pdf:2.58MB

The decarburization may take place depending on the chemical impurity composition in helium gas used as the primary coolant in High-Temperature Gas-cooled Reactors, and will significantly reduce the strength of the alloy. The ability to remove impurities by a helium purification system was designed according to the predicted generation rate of impurities so as to make the coolant become the carburizing atmosphere. It has been confirmed that the coolant becomes the carburizing atmosphere during the operation period of the High Temperature engineering Test Reactor (HTTR). However, it is necessary to consider changes of generation rates of impurities since lifetime of commercial reactor is longer than the life of the HTTR. To avoid the influence of the change of generation rate, the control of removal efficiency of impurity in the helium purification system was considered in this study. To reform the decarburizing into the carburizing atmosphere, it is effective to increase the H and CO concentration in the coolant helium. By controlling the efficiency of the Cooper Oxide Trap (CuOT), it is possible to increase the H and CO concentrations. Therefore, an experiment was carried out by injecting the gas mixture of H and CO into the existing purification system of HTTR to investigate the dependencies of temperature and impurity concentration on the removal efficiency of CuOT. The experimental results are described as the following, (1) By adjusting the temperature of helium at the CuOT within a range from 110C to 50C, it is possible to reduce the removal efficiency of H sufficiently. (2) Temperature change of helium gas in the CuOT is sufficiently reduced by the cooler located at the downstream of the CuOT, which does not affect the primary cooling system of HTTR. As the results, the applicability of removal efficiency control of CuOT was verified to improve the decarburizing atmosphere for the actual HTGR system.

A Gas-based neutron imaging detector with individual read-outs

Nakamura, Tatsuya; Tanaka, Hiroki; Yamagishi, Hideshi; Soyama, Kazuhiko; Aizawa, Kazuya; Ochi, Atsuhiko*; Tanimori, Toru*

Nuclear Instruments and Methods in Physics Research A, 573(1-2), p.187 - 190, 2007/04

https://doi.org/10.1016/j.nima.2006.10.238

We have been developing a neutron imaging gas detector with a high spatial resolution and with a high temporal response for the neutron scattering instruments at the pulsed neutron source in the Japan proton accelerator research complex. The gas detector system with individual read-outs was developed to meet the requirements for the instruments for neutron reflectometry or for small angle neutron scattering. The performances of the prototype detector using a multi-wire (MW) or micro-strip (MS) detector head were evaluated using a collimated neutron beam, and we confirmed the MS detector exhibiting a spatial resolution of 1.5 mm and a pulse-pair resolution of about 100 ns with a gas pressure of 6 atm helium with a mixture of 30% CF. The performances for the MS detector were also evaluated up to the total gas pressure of 8 atm.

Helium chemistry in high-temperature gas-cooled reactors; Chemistry control for avoiding Hastelloy XR corrosion in the HTTR-IS system

Sakaba, Nariaki; Hirayama, Yoshiaki*

Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 6 Pages, 2005/10

The high-temperature gas-cooled reactor (HTGR) is capable of producing a massive quantity of hydrogen with no carbon dioxide emission during its production by a thermo chemical IS (Iodine-Sulphur) process. The HTTR (High Temperature Engineering Test Reactor), which is the first high-temperature gas-cooled reactor in Japan, will be connected to some heat utilization system in the near future. The thermo chemical IS process is one of the progressive candidates. The metallic material of the heat transfer tube of the intermediate heat exchanger (IHX) and liner in the concentric hot gas duct in the HTTR-IS system, which allows usage in high-temperature conditions, is the nickel-based high-temperature alloy Hastelloy XR. Since the coolant helium contains small amounts of impurities, it is necessary to control the chemical composition in order to minimize corrosion of the Hastelloy XR. Major corrosion phenomena of the Hastelloy XR are carburization, decarburization, oxidation, and carbon deposition depending upon the particular gas composition and its temperature. The carburization and decarburization phenomena can be restricted by controlling the carbon activity and oxygen partial pressure. This paper describes the effect of each coolant impurity for the carburization and decarburization. Also a chemical composition limit was evaluated to avoid the Hastelloy XR corrosion.

Tritium recovery from solid breeder blanket by water vapor addition to helium sweep gas

Kawamura, Yoshinori; Iwai, Yasunori; Nakamura, Hirofumi; Hayashi, Takumi; Yamanishi, Toshihiko; Nishi, Masataka

Fusion Science and Technology, 48(1), p.654 - 657, 2005/07

https://doi.org/10.13182/FST05-A1010

Adding some amount of hydrogen to the helium sweep gas is effective for tritium extraction from blanket, but it causes permeation of tritium to a cooling system. In the design study of a demonstration reactor in JAERI, tritium leakage has been estimated to be about 20% of bred tritium under typical sweep gas conditions. If these tritiums are recovered under the ITER-WDS condition, tritium leakage limitation has to be less than 0.3% of typical case. Water vapor addition to the sweep gas is effective not only for blanket tritium extraction but also for permeation prevention. The reaction rate of isotope exchange is larger than the case of H, and the equilibrium constant is also expected to be about 1.0. When the H/T ratio is 100, tritium inventory of breeder material is larger than the case of H addition. However it is not so large. In case of HO sweep, separation of tritiated water from helium seems to be easyer, but the process that changes HTO to HT is necessary.

Development of 2-d position-sensitive neutron detector with individual readout; Operation test and establishment of detection system by means of neutron beam

Tanaka, Hiroki; Yamagishi, Hideshi; Nakamura, Tatsuya; Soyama, Kazuhiko; Aizawa, Kazuya

JAERI-Research 2005-010, 16 Pages, 2005/04

JAERI-Research-2005-010.pdf:3.39MB

We have been developing the 2-d position-sensitive neutron detector with individual readout as next-generation-type detector system for neutron scattering experiments using intense pulsed neutron source. The detection system is designed to fulfill the specifications required for each neutron spectrometer, such as a count rate, efficiency, neutron/-ray ratio, a spatial resolution and a size, by using suitable detector heads. The fundamental and imaging performances of the developed system assembled with a Multi-wire proportional counter head were evaluated using a collimated neutron beam. The system worked stably for long hours at the gas pressure of 5 atm with a mixture of 30% CH (0.26 atm He)at gas gain of 450. The spatial resolutions were 1.4, 1.6 mm (FWHM) for a cathode- and a back strip- direction, respectively, considering a beam size. It was also confirmed that the spatial uniformity of the detection efficiency over the whole sensitive detection area was rather good, 8 % deviation from the average with the optimum discrimination level.

Overview of goals and performance of ITER and strategy for plasma-wall interaction investigation

Shimada, Michiya; Costley, A. E.*; Federici, G.*; Ioki, Kimihiro*; Kukushkin, A. S.*; Mukhovatov, V.*; Polevoi, A. R.*; Sugihara, Masayoshi

Journal of Nuclear Materials, 337-339, p.808 - 815, 2005/03

https://doi.org/10.1016/j.jnucmat.2004.09.063

ITER is an experimental fusion reactor for investigation and demonstration of burning plasmas, characterised of its heating dominated by alpha-particle heating. ITER is a major step from present devices and an indispensable step for fusion reactor development. ITER's success largely depends on the control of plasma-wall interactions(PWI), with power and particle fluxes and time scales one or two orders of magnitude larger than in present devices. The strategy for control of PWI includes the semi-closed divertor, strong fuelling and pumping, disruption and ELM control, replaceable plasma-facing materials and stepwise operation.

Operation of a capillary plate under high-pressure He for neutron detection

Nakamura, Tatsuya; Masaoka, Sei; Yamagishi, Hideshi; Tanaka, Hiroki; Soyama, Kazuhiko; Aizawa, Kazuya

Nuclear Instruments and Methods in Physics Research A, 539(1-2), p.363 - 371, 2005/02

https://doi.org/10.1016/j.nima.2004.10.024

We evaluated the neutron-detection performance of a capillary plate under high-pressure helium-3 in terms of the gas gain and the distribution of pulse heights, with the aim of using the device as a neutron detector and a gas preamplification device. The capillary plate exhibited a gas gain of more than 1000 up to a gas pressure of 6 atm with a 5% mixture of ethane, confirming an adequate gas gain as a neutron detector. It was also found that the rise times of the signal pulses were correlated with the range and the emission angle of the secondary particles, protons and tritons, thereby providing useful information for developing a system with position-sensitive readouts with a high spatial resolution and a low background.