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Journal Articles

Development of the severe accident evaluation method on second coolant leakages from the PHTS in a loop-type sodium-cooled fast reactor

Yamada, Fumiaki; Imaizumi, Yuya; Nishimura, Masahiro; Fukano, Yoshitaka; Arikawa, Mitsuhiro*

Proceedings of 25th International Conference on Nuclear Engineering (ICONE-25) (CD-ROM), 10 Pages, 2017/07

The loss-of-reactor-level (LORL) is one of the loss-of-heat-removal-system (LOHRS) of beyond-DBA (BDBA) severe accident. An evaluation method for the LORL which is caused by the coolant leakage in two positions of the primary heat transport system (PHTS) was developed for prototype JSFR which is loop-type sodium-cooled fast reactor. The secondary leakage in cold standby which occurred in different loop from that of the first leakage in rated power operation can lead LORL by excessive declining of the sodium level. Therefore, the sodium level behavior in RV was studied in a representative accident sequence by considering the sodium pumping up into RV, siphon-breaking to stop pumping out from RV and maintain the sodium level, and calculation programs for the transient sodium level in RV. The representative sequence with lowest sodium level was selected by considering combinations of possible leakage positions. As a result of the evaluation considering the countermeasures above, it was revealed that the LOHRS can be prevented by maintaining the sodium level for the operation of decay heat removal system, even in the leakages in two positions of PHTS which corresponds to BDBA.

JAEA Reports

Research and development of a high-temperature helium-leak detection system, 1; Survey on leakage events and current leak detection technology (Joint research)

Sakaba, Nariaki; Nakazawa, Toshio; Kawasaki, Kozo; Urakami, Masao*; Saishu, Sadanori*

JAERI-Review 2002-041, 86 Pages, 2003/03

JAERI-Review-2002-041.pdf:3.21MB

In High Temperature Gas-cooled Reactors (HTGR), the detection of leakage of helium at an early stage is very important for the safety and stability of operations. Since helium is a colourless gas, it is generally difficult to identify the location and the amount of leakage when very little leakage has occurred. The purpose of this R&D is to develop a helium-leak detection system for the high temperature environment appropriate to the HTTR. This system can shorten the time of detection to several hours from about one week in the current detection time. In addition, it can also identify easily the leak location using the optical fibre network. As the first step in the development, this paper describes the result of surveying leakage events at nuclear facilities inside and outside Japan and current gas leakage detection technology to adapt optical fibre detection technology to HTGRs.

JAEA Reports

Research and development for a high-temperature helium-leak detection system, 3; Development of radiation sensors (Joint research)

Sakaba, Nariaki; Nakazawa, Toshio; Kawasaki, Kozo; Urakami, Masao*; Saishu, Sadanori*

JAERI-Research 2003-006, 65 Pages, 2003/03

JAERI-Research-2003-006.pdf:2.89MB

In the final third stage of the research and development for a high-temperature helium-leak detection system, the radiation sensor was developed in order to detect very small helium leakage. Applying the radiation sensor, we proposed not only the direct detection method which uses the detection of FP gas in helium, but also the active method which uses the difference in the radiation absorption between helium and air. From obtained data it was found that we can detect 0.2 cm$$^{3}$$/s leakage within 10 minutes by the active method.

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