Development of inspection and repair techniques for reactor vessel of experimental fast reactor "Joyo"; Replacement of upper core structure

Takamatsu, Misao; Kawahara, Hirotaka; Ito, Hiromichi; Ushiki, Hiroshi; Suzuki, Nobuhiro; Sasaki, Jun; Ota, Katsu; Okuda, Eiji; Kobayashi, Tetsuhiko; Nagai, Akinori; et al.

Nihon Genshiryoku Gakkai Wabun Rombunshi, 15(1), p.32 - 42, 2016/03

https://doi.org/10.3327/taesj.J15.003

In the experimental fast reactor Joyo, it was confirmed that the top of the irradiation test sub-assembly of "MARICO-2" (material testing rig with temperature control) had been broken and bent onto the in-vessel storage rack as an obstacle and had damaged the upper core structure (UCS). This paper describes the results of the in-vessel repair techniques for UCS replacement, which are developed in Joyo. UCS replacement was successfully completed in 2014. In-vessel repair techniques for sodium cooled fast reactors (SFRs) are important in confirming its safety and integrity. In order to secure the reliability of these techniques, it was necessary to demonstrate the performance under the actual reactor environment with high temperature, high radiation dose and remained sodium. The experience and knowledge gained in UCS replacement provides valuable insights into further improvements for In-vessel repair techniques in SFRs.

Inspection and repair techniques in the reactor vessel of the experimental fast reactor Joyo; Observation techniques development in a reactor vessel of the fast reactor, 2

Okuda, Eiji; Sasaki, Jun; Suzuki, Nobuhiro; Takamatsu, Misao; Nagai, Akinori

JAEA-Technology 2015-005, 36 Pages, 2015/03

JAEA-Technology-2015-005.pdf:44.42MB

In-Vessel Observations (IVO) techniques for Sodium cooled Fast Reactors (SFRs) are important in confirming its safety and integrity. In order to secure the reliability of IVO techniques, it was necessary to demonstrate the performance under the actual reactor environment with high temperature, high radiation dose and remained sodium. The IVO equipment for the Upper Core Structure (UCS) fitting area was specifically developed in the experimental fast reactor "Joyo". And the IVO was successfully completed as shown below. (1) Improvement of picture quality and resolution. The IVO of UCS fitting area with the gap of 5mm in minimum was achieved using the IVO equipment with video-scope under the actual reactor environment. The picture quality and resolution could be improved comparing with the radiation resistant fiberscope which was used in past IVO. (2) Prevention of video-scope hypofunction by high temperature / radiation dose. Since video-scope is inferior in thermal and radiation resistance, the IVO equipment was designed to be able to withdraw and insert video-scopes with cooling gas. This measure could achieve the observation in short radiation time with available temperature under the actual reactor environment. The IVO equipment for UCS fitting area provided useful information on UCS replacement. In addition, the experience provided valuable insights into further improvements for IVO techniques in SFRs.

Removal of cover gas boundary components on the rotating plug of the experimental fast reactor Joyo

Okuda, Eiji; Suzuki, Toshiaki; Fujinaka, Hideaki

JAEA-Technology 2013-038, 42 Pages, 2014/01

JAEA-Technology-2013-038.pdf:82.62MB

With the incident as an opportunity, repair techniques were developed in Joyo. The cover gas boundary components on rotating plug were removed as a preparation work for Joyo restoration work. The removed components are the door valve for fuel handling hole, hold-down shaft driving mechanism and door valve for inspection hole (A). Because these components were designed as the maintenance free. These components haven't been overhauled for more than 30 years since the construction of Joyo. Since the cover gas radioactivity was quite low due to the long time reactor shutdown, the new method was applied in this removal work. In order to prevent the contaminant of impurities in cover gas, the boundary was secured by temporary green house with slight negative pressure. Achievement of this work and accumulated experience will be able to provide valuable insights for further improving and verifying repair techniques in sodium cooled fast reactors.

An Estimation technique for compositions of bunsen reaction solutions on thermochemical water splitting is process

Kubo, Shinji; Nakajima, Hayato; Imai, Yoshiyuki; Kasahara, Seiji; Tanaka, Nobuyuki; Okuda, Hiroyuki; Miyashita, Reiko*; Onuki, Kaoru

Proceedings of 17th World Hydrogen Energy Conference (WHEC 2008) (CD-ROM), 4 Pages, 2008/06

A new technique was developed to estimate compositions of Bunsen reaction solution in liquid-liquid phase separation which was targeted on the two solutions in phase equilibrium. In this technique, just two densities measured in the two solution are employed to estimate compositions of two solutions consisting of HI, HSO, I, HO. The fundamental equations underlying this estimation is relations between densities and compositions. To formulate the relations, densities of simulated Bunsen reaction solutions were measured and regression expressions were formulated. Moreover, relational equations for both phases were set up from measured values by the regression procedure. Through estimations of both compositions from both densities, the calculated values are approximately consistent with titrated values. Because of easily and simply execution, this technique is useful for practical use, especially for plant operation and equipment design.

Study of ageing effect of long-term storage fuel in prototype fast breeder reactor Monju

Kato, Yuko; Umebayashi, Eiji; Okimoto, Yutaka; Okuda, Eiichi; Takayama, Koichi; Ozawa, Takayuki; Maeda, Seiichiro; Matsuzaki, Masaaki; Yoshida, Eiichi; Maeda, Koji; et al.

JAEA-Research 2007-019, 56 Pages, 2007/03

JAEA-Research-2007-019.pdf:6.79MB

In order to resume the System Startup Test (SST) of Monju, replacement fuel have to be loaded in exchange for some of initial fuel now loaded in the core to compensate core reactivity lost by decay of Pu-241 in them. The replacement fuel were being stored either in sodium in an ex-vessel storage tank or in air in a storage rack for about 10 years since their fabrication. The initial fuel were irradiated during the SST which was suspended in the end of 1995 and then stayed being loaded in the sodium-circulated core. As this long-term storage and loading may deteriorate mechanical integrity of the assemblies, a study has been made thoroughly on its thermal-hydraulic, structural and material effects on them that might be caused by irradiation in the core, sodium and mechanical environment. The study has shown that the mechanical integrity of them is well maintained even with this long-term storage and loading.

Optimization of the process parameters of an electrochemical cell in the IS process

Nomura, Mikihiro*; Okuda, Hiroyuki; Kasahara, Seiji; Nakao, Shinichi*

Chemical Engineering Science, 60(24), p.7160 - 7167, 2005/12

https://doi.org/10.1016/j.ces.2005.07.011

The Bunsen reaction (SO+I+2HO=HSO+2HI) in the water-splitting IS process was examined using an electrochemical cell with a cation exchange membrane. The optimal molalities of anolyte and catholyte were evaluated by total thermal efficiency. The I/HI ratio had little effect on the required total voltage; the I/HI ratio can be reduced to 0.5 without decreasing the efficiency. HI and HSO molality greatly affected the efficiency. Membrane resistances are very important parameters affecting the efficiency. The total thermal efficiency increased by 3.0% by increasing the operating temperature from 313K to 363K.

Application of membrane systems to the IS process

Onuki, Kaoru; Kasahara, Seiji; Tanaka, Nobuyuki; Okuda, Hiroyuki; Yoshida, Mitsunori; Hodotsuka, Masatoshi; Iwatsuki, Jin; Imai, Yoshiyuki; Noguchi, Hiroki; Terada, Atsuhiko; et al.

no journal, , 

Development of efficient HI processing scheme is important for attaining high thermal efficiency of hydrogen production by IS process. We are studying an application of electro-electrodialysis to pre-concentrate the HIx solution before distillation, which is supplied from the Bunsen reaction section. So far, feasibility of the pre-concentration was experimentally verified and also, by flowsheet analysis, the importance was clarified of improving the performance of membrane and electrode catalyst.

R&D on thermochemical water-splitting iodine-sulfur process for hydrogen production

Onuki, Kaoru; Kubo, Shinji; Terada, Atsuhiko; Sakaba, Nariaki; Iwatsuki, Jin; Okuda, Hiroyuki; Kasahara, Seiji; Tanaka, Nobuyuki; Imai, Yoshiyuki; Noguchi, Hiroki; et al.

no journal, , 

Japan Atomic Energy Agency has been conducting R&D on thermochemical water-splitting process for hydrogen production. "Closed-cycle" operation features the thermochemical processes, with which all the reactants except water are cyclically used in the component chemical reactions. The closed-cycle operation of pure-thermochemical Iodine-Sulfur process was demonstrated for one week using a glass-made apparatus with hydrogen production rate of about 30NL/h. "Corrosion" is another big technical issue. Based on preliminary corrosion tests in the typical process environments, sulfuric acid decomposer for vaporizing concentrated sulfuric acid at 300-500C and at 2MPa using the sensible heat of high temperature helium gas was designed featuring a heat exchanger made of silicon carbide. Test-fabrication of the ceramic heat exchanger was performed with the capacity equivalent to the hydrogen production rate of 30Nm/h.

Restoration for damaged components in reactor vessel of the experimental fast reactor Joyo

Okuda, Eiji; Ito, Chikara; Takamatsu, Misao; Ashida, Takashi; Ito, Hideaki; Nagai, Akinori

no journal, , 

In the experimental fast reactor Joyo, it was confirmed that the top of the irradiation test Sub-Assembly (S/A) of "MARICO-2" (material testing rig with temperature control) had bent onto the in-vessel storage rack (IVS) as an obstacle and had damaged the Upper Core Structure (UCS). This incident necessitates the replacement of the UCS and the retrieval of MARICO-2 S/A for Joyo re-start. Along with four stages involving jack-up and retrieval of the existing damaged UCS (ed-UCS), retrieval of the MARICO-2 S/A, and installation of the new UCS (n-UCS) in the restoration work plan, current conditions at Joyo are being carefully investigated, and the results are applied to the designs of special handling equipment, which is being manufactured and scheduled for operation in 2014.

Inspection and repair techniques in reactor vessel of sodium cooled fast reactor, 9-6; Development of in-vessel observation techniques for UCS replacement

Sasaki, Jun; Okuda, Eiji; Suzuki, Nobuhiro; Ota, Katsu; Owada, Ryohei; Takamatsu, Misao

no journal, , 

no abstracts in English