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Journal Articles

Prototype fast breeder reactor "Monju" start of unloading operation of the fuel assembly from the core

Koga, Kazuhiro*; Suzuki, Kazunori*; Takagi, Tsuyohiko; Hamano, Tomoharu

FAPIG, (196), p.8 - 15, 2020/01

The prototype fast breeder reactor Monju has already started (from June 2017) the unloading operation period (about 5.5 years: until the end of 2022) of the fuel assembly, which is the first stage of decommission. Among them, the first "Processing of fuel assembly" operation (86 in total) was conducted from August 2018 to January 2019 as the first handling of the fuel assembly. Fuji Electric provided technical support, such as dispatching technicians throughout the period, in cooperation with Japan Atomic Energy Agency for the "Processing of fuel assembly" operation, and contributed to the completion of the operation while experiencing various troubles. This manuscript introduces the contents of the first "Processing of fuel assembly" operation and the overview of the trouble status. This manuscript is a sequel to FAPIG No.194 "Prototype Fast Breeder Reactor Monju Decommissioning and Unloading Operation of the Fuel Assembly from the Core", please refer to it.

Journal Articles

Irradiation induced reactivity in Monju zero power operation

Takano, Kazuya; Maruyama, Shuhei; Hazama, Taira; Usami, Shin

Proceedings of Reactor Physics Paving the Way Towards More Efficient Systems (PHYSOR 2018) (USB Flash Drive), p.1725 - 1735, 2018/04

Irradiation dependence of the core excess reactivity was investigated for the Monju system startup tests at zero-power carried out in 2010. The excess reactivity basically decreases with the $$beta$$ decay of $$^{241}$$Pu in zero-power operation. However, the excess reactivity little changed in the two month period of the startup tests, which suggests a positive reactivity insertion during the period. The investigated irradiation dependence shows that the positive reactivity increases with reactor operation and mostly saturates by the fission-dose attained during the Monju zero-power operation in a month ($$sim$$10$$^{17}$$ fissions/cm$$^{3}$$). The saturated positive reactivity is equivalent to approximately 47% of the initially accumulated self-irradiation damage recovery assuming the defects were recovered by the fission-fragment irradiation in the reactor operation.

JAEA Reports

Verification of alternative dew point hygrometer for CV-LRT in Monju

Ichikawa, Shoichi; Chiba, Yusuke; Ono, Fumiyasu; Hatori, Masakazu; Kobayashi, Takanori; Uekura, Ryoichi; Hashiri, Nobuo*; Inuzuka, Taisuke*; Kitano, Hiroshi*; Abe, Hisashi*

JAEA-Research 2016-021, 32 Pages, 2017/02

JAEA-Research-2016-021.pdf:5.0MB

In order to reduce the influence on a plant schedule of the MONJU by the maintenance of dew point hygrometers, The JAEA examined a capacitance type dew point hygrometer as an alternative dew point hygrometer for a lithium-chloride type dew point hygrometer which had been used at the CV-LRT in the MONJU. As a result of comparing a capacitance type dew point hygrometer with a lithium-chloride type dew point hygrometer at the CV-LRT (Atmosphere: nitrogen, Testing time: 24 hours), there weren't significant difference between a capacitance type dew point hygrometer and a lithium-chloride type dew point hygrometer. As a result of comparing a capacitance dew point hygrometer with a high-mirror-surface type dew point hygrometer for long term verification (Atmosphere: air, Testing time: 24 months), the JAEA confirmed that a capacitance type dew point hygrometer satisfied the instrument specification ($$pm$$2.04$$^{circ}$$C) required by the JEAC4203-2008.

JAEA Reports

Annual technical report of the prototype fast breeder reactor Monju; 2013

Fast Breeder Reactor Research and Development Center, Tsuruga Head Office

JAEA-Review 2014-030, 138 Pages, 2014/08

JAEA-Review-2014-030.pdf:71.69MB

The prototype fast breeder reactor Monju has accumulated technical achievements in order to establish the fast breeder reactor cycle technology in Japan using the operation and maintenance experience, etc. This annual report summarizes the primary achievements and the data related to the plant management in Monju during fiscal 2013.

Oral presentation

The Findings from the survey of crush zones at the fast breeder prototype reactor Monju site

Ishimaru, Tsuneari; Shimada, Koji; Sueoka, Shigeru; Yasue, Kenichi; Niwa, Masakazu; Umeda, Koji

no journal, , 

The Nuclear Regulation Authority (NRA) instructed to develop a further additional research plan regarding the crushed zones on the Monju site against the JAEA on September 25, 2013. The JAEA developed a research plan in response to this instruction, and, the stripping investigation with expansion of the area, the additional detailed geographical and geological surveys in the mountains/terrace boundary, and the marine seismic surveys in the coastal waters, were conducted. And, the JAEA was submitted to the NRA "Compilation Report" on March 28, 2014. From the investigation results so far, no clear evidence was observed to support that the on-site crushed zones are active faults. And, in the sea and land vicinity of the site, other than to the Shiraki-Nyu active fault, structure associated with the active fault is not recognized. From the plastic deformation of the biotite which is observed in the latest shear plane, the on-site crushed zones are considered to be a geological structure of the pre-Quaternary, which is formed in the deep underground environment of the several kilometers.

Oral presentation

Activity evaluation of fracture zone in granitic rock; Case study on the survey of fracture zones at the fast breeder prototype reactor "Monju" site

Ishimaru, Tsuneari; Shimada, Koji; Sueoka, Shigeru; Yasue, Kenichi; Niwa, Masakazu; Umeda, Koji

no journal, , 

In JAEA, geological investigation of fracture zones has been carried out at the Monju site based on the instruction received from the Nuclear Regulation Authority. Results of the investigation, it has shown that no clear evidence was observed to indicate that on-site fracture zones are active faults. In the activity evaluation of the on-site fracture zones, we examined cross-cutting relationships of fractures in detail, and we estimated that these fracture zones are older small-scale geological structure which was formed under the high-temperature environment of the deep part before exposure of the granitic body from the microscopic observation of the plastic deformation of biotite grains in the fracture zones and the deformation twins in the calcite veins along the fracture zones. This investigation of fracture zones is considered one of good examples shown that it is possible to evaluated activity of fracture zones in granite.

Oral presentation

An Example of activity evaluation of minor crush zone including subparallel clay veins in granite near the Monju site

Shimada, Koji; Ishimaru, Tsuneari; Sueoka, Shigeru; Terusawa, Shuji; Yasue, Kenichi; Niwa, Masakazu; Umeda, Koji

no journal, , 

Diverse situation of outcropping crush zones around important building constructions need upgrading of activity evaluation method without the use of overlying sediments. The method using the cross-cutting relations among geologic features in basement rocks is promising. However, minor crush zones without cross-cutting relation are frequently observed. An activity evaluation of such minor crush zone was carried out in one outcrop. The confirmation of an extension of the crush zone, age estimation of young overlying sediments, comparison of sense of shear of clay vein, comparison of outcrop morphology with another crush zone, and clay grain-size measurement of the near active fault and the crush zone are carried out. The results suggest that the crush zone is not an active fault or a weak zone which slips accompanied with the active zone.

Oral presentation

A Method to assess the activity of crush zones alternative to the application of overlying sediments

Shimada, Koji; Sueoka, Shigeru; Ishimaru, Tsuneari

no journal, , 

The application of overlying sediments is one of the methods defining relative age based on the principle of cross-cutting relations. This principle is one of the geological principles indicating relative age of deformation features such as faulting or tectono-metamorphic textures. The application of overlying sediments and relative age determination of deformation features are also based on the principle of cross-cut relations. We present a method utilize relative deformation age by means of the cross-cut relations, temperature gauges shown by structures, and thermal history of geological body alternative to the application of overlying sediments. Research area is located near the FBR Monju. Data suggest that the activity of crush zones precede basaltic dyke formation under higher temperature environment. This research method is potential alternative, though case study is needed towards overcoming the unsuitable outcropping situation to grasp basic geological data.

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