Achievement of safety demonstration tests using HTTR; Loss of forced cooling test at 100% reactor power (30 MW)

Nagasumi, Satoru; Hasegawa, Toshinari; Nakagawa, Shigeaki; Kubo, Shinji; Iigaki, Kazuhiko; Shinohara, Masanori; Saikusa, Akio; Nojiri, Naoki; Saito, Kenji; Furusawa, Takayuki; et al.

JAEA-Research 2025-005, 23 Pages, 2025/07

JAEA-Research-2025-005.pdf:2.68MB

A safety demonstration test under abnormal operating conditions using the HTTR (High Temperature Engineering Test Reactor) was conducted to demonstrate safety features of the HTGRs (High Temperature Gas-cooled Reactors). Under a simulation of a control rod shutdown failure, all primary helium gas circulators were intentionally stopped during a steady-state operation at 100% reactor thermal power (30 MW), temporal changes of the reactor power and temperatures around the reactor pressure vessel (RPV) were obtained after the complete loss of forced heat removal from the reactor core. After the event (primary coolant flow stopped), the reactor power quickly decreased due to the negative reactivity feedback associated with the core temperature rise, and then the reactor power spontaneously shifted to a stable state of low power (about 1.2%) even after a recriticality. Heat dissipation from RPV surface to a surrounding vessel cooling system (water-cooled panels) ensured the amount of heat removal required to maintain the reactor temperature constant in the low power state. In this way, the transition from the event occurrence to the stable and safety state, i.e., inherent safety features of HTGRs, were demonstrated in the case of core forced cooling loss without active shutdown operations.

Investigation of deposits on filter element of primary gas circulators in HTTR

Hasegawa, Toshinari; Nagasumi, Satoru; Nemoto, Takahiro; Nakajima, Kunihiro; Yokoyama, Keisuke; Fujiwara, Yusuke; Arakawa, Ryoki; Iigaki, Kazuhiko; Inoi, Hiroyuki; Kawamoto, Taiki

Proceedings of 2024 International Congress on Advanced in Nuclear Power Plants (ICAPP 2024) (Internet), 10 Pages, 2024/06

The filter element of the primary gas circulators (PGC) in High Temperature engineering Test Reactor (HTTR) and its deposits were investigated by Scanning Electron Microscope (SEM) observation and Energy Dispersive X-ray spectroscopy (EDX) analysis to find the cause of the increase of the filter differential pressure during the operation in 2021. SEM observation showed that the clumpy deposits and fibrous deposits smaller than the filtration pore size and the rod-shaped deposits larger than the pore size were present on the filter element. EDX analysis showed that the clumpy deposits and fibrous deposits could include silicone oil in the primary helium purification system (PHPS) gas circulators and that the rod-shaped deposits were thermal insulators inside of the co-axial double pipes in the primary cooling system. It is considered that silicone oil leaked from the PHPS gas circulators due to deterioration in the absorption performance of the activated charcoal filter. Next, it could be vaporized and reach PGC's filter element after passing through the reactor core. Since those deposits including silicone oil were present over the entire surface of the filter element, the filter differential pressure could be increased due to a reduction in the pore size and a rise in its flow resistance. The thermal insulator was unrelated to filter clogging because it was present mainly in the lower part of the filter element. Therefore, silicone oil could increase the filter differential pressure, and the graphite powder, which is the cause of the previous issue was unrelated.

High temperature gas-cooled reactors

Takeda, Tetsuaki*; Inagaki, Yoshiyuki; Aihara, Jun; Aoki, Takeshi; Fujiwara, Yusuke; Fukaya, Yuji; Goto, Minoru; Ho, H. Q.; Iigaki, Kazuhiko; Imai, Yoshiyuki; et al.

High Temperature Gas-Cooled Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.5, 464 Pages, 2021/02

https://doi.org/10.1016/C2018-0-05383-9

As a general overview of the research and development of a High Temperature Gas-cooled Reactor (HTGR) in JAEA, this book describes the achievements by the High Temperature Engineering Test Reactor (HTTR) on the designs, key component technologies such as fuel, reactor internals, high temperature components, etc., and operational experience such as rise-to-power tests, high temperature operation at 950C, safety demonstration tests, etc. In addition, based on the knowledge of the HTTR, the development of designs and component technologies such as high performance fuel, helium gas turbine and hydrogen production by IS process for commercial HTGRs are described. These results are very useful for the future development of HTGRs. This book is published as one of a series of technical books on fossil fuel and nuclear energy systems by the Power Energy Systems Division of the Japan Society of Mechanical Engineers.

Proton-exchange mechanism of specific Cs adsorption lattice defect sites of Prussian blue filled with coordination and crystallization water molecules

Ishizaki, Manabu*; Akiba, Sae*; Otani, Asako*; Hoshi, Yuji*; Ono, Kenta*; Matsuba, Mayu*; Togashi, Takanari*; Kanaizuka, Katsuhiko*; Sakamoto, Masatomi*; Takahashi, Akira*; et al.

Dalton Transactions, 42(45), p.16049 - 16055, 2013/12

https://doi.org/10.1039/c3dt51637g

We have revealed the fundamental mechanism of specific Cs adsorption into Prussian blue (PB) in order to develop high-performance PB-based Cs adsorbents in the wake of the Fukushima nuclear accident. We compared two types of PB nanoparticles with formulae of Fe[Fe(CN)]3xHO (x = 10-15) (PB-1) and (NH)0.70Fe1.10[Fe(CN)]1.7HO (PB-2) with respect to the Cs adsorption ability. The synthesised PB-1, by a common stoichiometric aqueous reaction between 4Fe and 3[Fe(CN)], showed much more efficient Cs adsorption ability than did the commercially available PB-2.

Preparation of a film of copper hexacyanoferrate nanoparticles for electrochemical removal of cesium from radioactive wastewater

Chen, R.*; Tanaka, Hisashi*; Kawamoto, Toru*; Asai, Miyuki*; Fukushima, Chikako*; Kurihara, Masato*; Watanabe, Masayuki; Arisaka, Makoto; Nankawa, Takuya

Electrochemistry Communications, 25, p.23 - 25, 2012/11

https://doi.org/10.1016/j.elecom.2012.09.012

We first synthesized water-dispersed nanoparticle copper hexacyanoferrate (CuHCF) ink and then coated its nanoparticles on electrodes to electrochemically remove cesium from wastewater. Cesium uptake and elution can be controlled by switching the potentials between anodes and cathodes. Effective cesium removal can be adopted in a large pH range from 0.2 to 8.9, and in the presence of several diverse coexisting alkaline cations, suggesting that it can be taken as a promising technology for actual radioactive wastewater treatment. The prepared CuHCF nanoparticles can be simply and uniformly coated on electrodes by wet process like conventional printing methods, so any sizes or patterns are feasible at low cost, which indicated the potential as a promising sorption electrode of large size in the columns for sequential removal and recycle of Cs from wastewater.

Efficient electrochemical cesium recovery with copper hexacyanoferrate complex

Tanaka, Hisashi*; Asai, Miyuki*; Fukushima, Chikako*; Kawamoto, Toru*; Kurihara, Masato*; Arisaka, Makoto; Nankawa, Takuya; Watanabe, Masayuki

no journal, , 

Copper hexacyanoferrate complex could be repetitively adsorb cesium cation in terms of electrochemical reduction and oxidation. We demonstrated the adsorption performance of the thin membrane electrode which copper hexacyanoferrate complex was formed on a metal electrode and also attempted thickening of the copper hexacyanoferrate complex layer on the electrode. The copper hexacyanoferrate complex electrochemically adsorbed about 90% of Cs from the solution by 4 times repetition of the adsorption cycle. The electrochemical efficiency of the adsorption increased 50 times by thickening of the copper hexacyanoferrate complex layer on the electrode.

Study on tritium production for initial fusion reactor using high temperature gas cooled reactor; Improvement of the tritium containment performance by concentrating Li compound

Nakaya, Hiroyuki*; Matsuura, Hideaki*; Kawamoto, Yasuko*; Nagasumi, Satoru*; Katayama, Kazunari*; Goto, Minoru; Nakagawa, Shigeaki

no journal, , 

We proposed the used of High Temperature Gas-cooled Reactors (HTGR) as a tritium production device, which produces tritium by Li(n,)T reaction, for initial fusion reactors. Concentrating of Li suppresses undesirable leakage of produced tritium into reactor coolant. In this study, the effect of Li concentration difference on the amount of the tritium leakage and the tritium production efficiency was investigated.

Influence of coexisting ions to cesium adsorption electrode of nanoparticle copper hexacyanoferrate

Tanaka, Hisashi*; Chen, R.*; Asai, Miyuki*; Fukushima, Chikako*; Kawamoto, Toru*; Ishizaki, Manabu*; Kurihara, Masato*; Arisaka, Makoto; Nankawa, Takuya; Watanabe, Masayuki

no journal, , 

Hexacyanoferrate metal Complex (MHCF) is well-known as adsorption materials for Cesium ion. We have developed the effective processing method by making MHCF of nano particle ink. In this paper, we investigated the effect of the presence of other metal cations on electrochemical adsorption and desorption of cesium.

Compact Cs separation by electrochemical adsorption/desorption using copper hexacyanoferrate film in a column system

Chen, R.*; Tanaka, Hisashi*; Fukushima, Chikako*; Asai, Miyuki*; Kawamoto, Toru*; Kurihara, Masato*; Ishizaki, Manabu*; Arisaka, Makoto; Nankawa, Takuya; Watanabe, Masayuki

no journal, , 

Transition metal hexacyanoferrates (MHCFs) are preferred to be competitive ion exchangers over other materials due to their selectivity and high capacity. CuHCF has been much used as precipitants for alkali metal cations, especially cesium, to remove them from aqueous radioactive wastes. Instated of the conventional adsorption by using copper hexacyanoferrate powder, we developed and coated the CuHCF nanoparticles on the electrode substance, and then performed Cs removal in an electrochemical column System. The objective of this study was to develop a nanoparticle film of CuHCF for Cs removal and to suggest a promising column technology for sequential removal of actual radiocesium wastewater.