A Study for a fire gas behavior by using a vertical shaft model (Contract research)

Abe, Hironobu; Hatakeyama, Nobuya; Yamazaki, Masanao; Okuzono, Akihiko*; Sakai, Tetsuo*; Inoue, Masahiro*

JAEA-Research 2009-019, 192 Pages, 2020/02

JAEA-Research-2009-019.pdf:8.07MB

Construction of the underground facility is on going at the Horonobe Underground Research Center, a division of the Japan Atomic Energy Agency. The facility is consisted of three shafts and horizontal drifts at the completion of construction and it is excavated in geological environment with methane gas, so it is important to secure the workers and visitors security in case of fire in the underground. However, it is known that the fire gas such as methane shows a complicated behavior by drift effect and so on and very difficult to predict its behavior, even if under enforced ventilation. In order to construct new prediction method of the fire gas behavior, the model scaled experiments were conducted by using the basic model which consists of shafts and drifts. As a results, fundamental data of the fire gas behavior was grasped and complicated behavior of the fire gas such as three-dimensional backflow and main flow inversion phenomena at the underground structure were ascertained. A new fire gas behavior analysis system has been designed and a prototype system has been programmed which is able to simulate the phenomena noted above. Coupling analysis method is adapted to the system, which consists of mainly one-dimensional ventilation network analysis and simplified computational fluid dynamics program named M-CFD. To minimize calculation time, M-CFD was designed as two-dimensional calculation with simulators multi area analysis system. Using the prototype system, several experimented models representing typical behavior of fire gas have been simulated for model scaled experiments. The system qualitatively reappeared the phenomena such as back flow or main flow inversion, and most of calculations completed in expected time. This indicates appropriateness of the prototype system, but some upgrade such as heat conductivity analysis in the wall rock mass transfer calculation, user friendly interface system and others will be required.

Development of a laser chipping technique combined with water jet for retrieval of fuel debris at Fukushima Daiichi Nuclear Power Station

Yamada, Tomonori; Takebe, Toshihiko*; Ishizuka, Ippei*; Daido, Hiroyuki*; Hanari, Toshihide; Shibata, Takuya; Omori, Shinya*; Kurosawa, Koichi*; Sasaki, Go*; Nakada, Masahiro*; et al.

Journal of Nuclear Science and Technology, 56(12), p.1171 - 1179, 2019/12

https://doi.org/10.1080/00223131.2019.1647890

We describe a new chipping technique combined with a water-jet technique as one of the candidate techniques for the retrieval of fuel debris and support structures as part of the decommissioning of the Fukushima Daiichi Nuclear Power Station. We performed proof-of-principle experiments to demonstrate the removal capability of metal parts, where we focused on the observation of removal processes from a metallic sample using a 5.5-kW continuous wave fiber laser combined with continuous and pulsed water jets.

Demonstration of laser processing technique combined with water jet technique for retrieval of fuel debris at Fukushima Daiichi Nuclear Power Station

Hanari, Toshihide; Takebe, Toshihiko*; Yamada, Tomonori; Daido, Hiroyuki; Ishizuka, Ippei*; Omori, Shinya*; Kurosawa, Koichi*; Sasaki, Go*; Nakada, Masahiro*; Sakai, Hideaki*

Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 3 Pages, 2017/04

In decommissioning of Fukushima Daiichi Nuclear Power Station, a retrieval process of fuel debris in the Primary Containment Vessel by a remote operation is one of the key issues. In this process, prevention of spreading radioactive materials is one of the important considerations. Furthermore, an applicable technique to the process requires keeping of reasonable processing-efficiency. We propose to use the combined technique including a laser light and a water jet as a retrieval technique of the fuel debris. The laser processing technique combined with a repetitive pulsed water jet could perform an efficient retrieval processing. Our experimental result encourages us to promote further development of the technique towards a real application at Fukushima Daiichi Nuclear Power Station.

Using LiF crystals for high-performance neutron imaging with micron-scale resolution

Faenov, A.*; Matsubayashi, Masahito; Pikuz, T.*; Fukuda, Yuji; Kando, Masaki; Yasuda, Ryo; Iikura, Hiroshi; Nojima, Takehiro; Sakai, Takuro; Shiozawa, Masahiro*; et al.

High Power Laser Science and Engineering, 3, p.e27_1 - e27_9, 2015/10

https://doi.org/10.1017/hpl.2015.28

Evaluation of protection factors of a breath-responsive-powered air-purifying respirator

Nakagawa, Masahiro; Nojima, Shun; Fujii, Katsutoshi; Shishido, Nobuhito; Sakai, Toshiya; Umehara, Takashi; Shimizu, Isamu

Hoken Butsuri, 47(3), p.189 - 193, 2012/10

https://doi.org/10.5453/jhps.47.189

It is essential to wear an air-purifying respirator in the radiation works in a contaminated atmosphere. A breath-responsive-powered air-purifying respirator (BR-PAPR) has been recently developed. However, no research has yet been conducted to determine the protection factor (PF) of the BR-PAPR in actual workplaces. In this study, the PFs of the BR-PAPR were measured by a man-test apparatus and compared with those of a non-powered full face mask. The PFs were measured under three different situations; normal wearing condition, clogging the filter and leaving a gap between the face and the mask. Under these situations, it was found that the PFs of the BR-PAPR are higher than those of the non-powered full face mask. PFs greater than 4000 were obtained for 95% of the subjects who wear the BR-PAPR, and PFs over 6667, the upper limit of the man-test apparatus, were obtained for 49% of them. The questionnaire survey was conducted for workers. The results showed that the workers feel a reduced burden when they wear the BR-PAPR. The results of this study showed high protection performance and operation efficiency of the BR-PAPR.

Study on evaluation methodology for groundwater flow based on geochemical data; Case study for Horonobe area (Contract research)

Sakai, Ryutaro; Munakata, Masahiro; Kimura, Hideo

JAEA-Research 2011-054, 19 Pages, 2012/03

JAEA-Research-2011-054.pdf:2.07MB

In the safety assessment for a geological disposal of radioactive waste, it is important to establish validation methods for deep groundwater flow system to estimate radionuclide migration to human environment through groundwater flow. This study discussed the method which estimates groundwater mixing condition and groundwater flow process using principal component analysis (PCA) to groundwater chemistry and isotopic compositions, together with data of groundwater age and trace element in case of Horonobe area. The results show that hydrochemical system can be divided into two systems: (1) three deep groundwater mixing system at depths greater than 200 to 400 m, (2) mixing area of deep groundwater and surface water at depths less than 200 to 400 m. Groundwater in the deep aquifer is suggested to be discharged at surface through Omagari Fault.

Study on validation method of regional groundwater flow model; Case study for Horonobe area and Niigata basin (Contract research)

Sakai, Ryutaro; Munakata, Masahiro; Kimura, Hideo; Ooka, Masao*; Seguchi, Mariko*

JAEA-Research 2011-029, 24 Pages, 2011/11

JAEA-Research-2011-029.pdf:3.67MB

In the safety assessment for a geological disposal of radioactive waste, it is important to establish validation methods for regional groundwater flow system to estimate radionuclide migration to human environment through groundwater flow. It is necessary to validate the groundwater flow property and flow boundary, as multi-groundwater systems including the different groundwater origins are possible to exist at deep underground. This results show that mixing analysis based on hydrochemical data and spatial plotting with hydrochemical data and thermal data are applicable to validate groundwater flow pattern and groundwater flow boundary in case of Horonobe area. It also demonstrates that mixing analysis based on hydrochemical data and spatial plotting with hydrological and hydrochemical data are applicable to validate the groundwater flow property and groundwater flow boundary in case of Nagaoka area.

Evaluation of water distribution in a small operating fuel cell using neutron color image intensifier

Yasuda, Ryo; Nitto, Koichi*; Konagai, Chikara*; Shiozawa, Masahiro*; Takenaka, Nobuyuki*; Asano, Hitoshi*; Murakawa, Hideki*; Sugimoto, Katsumi*; Nojima, Takehiro; Hayashida, Hirotoshi; et al.

Nuclear Instruments and Methods in Physics Research A, 651(1), p.268 - 272, 2011/09

https://doi.org/10.1016/j.nima.2011.01.175

Neutron radiography is one of useful tools to visualize water behavior in fuel cells under operation. In order to observe the detailed information about the water distribution in MEA and GDL in fuel cells, a high spatial resolution and high sensitivity neutron imaging system are required. We developed an imaging system using the neutron color imaging intensifier and continuously observed water distribution in operating a fuel cell. By using the system, a small type fuel cell under operation was continuously observed at the TNRF in every 20 sec. In the results, the water area was appeared from GDL and MEA, and expanded to the channel of the cathode side. On the other hand, voltage was gradually reduced with the operation time, and steeply dropped. It is considered that voltage drop was caused by blockage of gas flow due to the piling up water in the channel of the cathode side.

Identified charged hadron production in collisions at = 200 and 62.4 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review C, 83(6), p.064903_1 - 064903_29, 2011/06

https://doi.org/10.1103/PhysRevC.83.064903

Transverse momentum distributions and yields for , and in collisions at = 200 and 62.4 GeV at midrapidity are measured by the PHENIX experiment at the RHIC. We present the inverse slope parameter, mean transverse momentum, and yield per unit rapidity at each energy, and compare them to other measurements at different collisions. We also present the scaling properties such as and scaling and discuss the mechanism of the particle production in collisions. The measured spectra are compared to next-to-leading order perturbative QCD calculations.

Azimuthal correlations of electrons from heavy-flavor decay with hadrons in and Au+Au collisions at = 200 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Aramaki, Y.*; et al.

Physical Review C, 83(4), p.044912_1 - 044912_16, 2011/04

https://doi.org/10.1103/PhysRevC.83.044912

Measurements of electrons from the decay of open-heavy-flavor mesons have shown that the yields are suppressed in Au+Au collisions compared to expectations from binary-scaled collisions. Here we extend these studies to two particle correlations where one particle is an electron from the decay of a heavy flavor meson and the other is a charged hadron from either the decay of the heavy meson or from jet fragmentation. These measurements provide more detailed information about the interaction between heavy quarks and the quark-gluon matter. We find the away-side-jet shape and yield to be modified in Au+Au collisions compared to collisions.