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Journal Articles

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

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 950$$^{circ}$$C, 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.

Journal Articles

Development of observation techniques in reactor vessel of experimental fast reactor Joyo

Takamatsu, Misao; Imaizumi, Kazuyuki; Nagai, Akinori; Sekine, Takashi; Maeda, Yukimoto

Journal of Power and Energy Systems (Internet), 4(1), p.113 - 125, 2010/00

During the investigation of an incident that occurred with the experimental fast reactor Joyo, in-vessel observations using a standard Video Camera (VC) and a Radiation-Resistant Fiberscope (RRF) took place at (1) the top of the Sub-Assemblies (S/As) and the In-Vessel Storage rack (IVS), (2) the bottom face of the Upper Core Structure (UCS) under the condition with the level of sodium at -50 mm below the top of the S/As. A simple 6 m overhead view of each S/A, through the fuel handling or inspection holes etc, was photographed using a VC fixed to the rotating-plug with the acrylic panel for making observations of the top of S/As and IVS. About 650 photographs were required to create a composite photograph of the top of the entire S/As and IVS, and a resolution was estimated to be approximately 1 mm. In order to observe the bottom face of the UCS, a remote handling device equipped with RRFs (approximately 13 m long) was specifically developed for Joyo with a tip that could be bent into an L-shape and inserted into the 70 mm gap between the top of the S/As and the bottom of the UCS. A total of about 35,000 photographs were needed for the full investigation. Regarding the resolution, the sodium flow regulating grid of 0.8 mm in thickness could be discriminated, and the base of thermocouple sleeves 6 mm in diameter located 450 mm above the top of S/As were also clearly observed. In both types of observations, it was confirmed that lighting adjustments play a critical role. Particularly in narrow space observations, scattered lighting with automatic dimming controlled light source was available for achieving close observations of the in-vessel structures. In addition to the successful result of the incident investigation, these experiments provided valuable insights for use in further improving and verifying in-vessel observation techniques in sodium cooled fast reactors.

Journal Articles

Development of observation techniques in reactor vessel of experimental fast reactor Joyo

Takamatsu, Misao; Imaizumi, Kazuyuki; Nagai, Akinori; Sekine, Takashi; Maeda, Yukimoto

Proceedings of 17th International Conference on Nuclear Engineering (ICONE-17) (CD-ROM), 10 Pages, 2009/07

During the investigation of an incident in Joyo, in-vessel observations using a Video Camera (VC) and a Radiation-Resistant Fiberscope (RRF) took place at (1) the top of the Sub-Assemblies (S/As) and the In-Vessel Storage rack (IVS), (2) the bottom face of the Upper Core Structure (UCS). A simple 6 m overhead view of each S/A was photographed using a VC fixed to the rotating-plug for making observations of the top of S/As and IVS. A resolution was estimated to be approximately 1mm. In order to observe the bottom face of the UCS, a remote handling device equipped with RRFs was specifically developed for Joyo with a tip that can be bent into an L-shape and inserted into the 70 mm gap between the top of the S/As and the bottom of the UCS. The sodium flow regulating grid of 0.8mm in thickness could be discriminated. These experiments provided valuable insights for use in further improving and verifying in-vessel observation techniques in sodium cooled fast reactors.

Journal Articles

In-vessel visual inspection of experimental fast reactor Joyo

Itagaki, Wataru; Sekine, Takashi; Imaizumi, Kazuyuki; Maeda, Shigetaka; Ashida, Takashi; Takamatsu, Misao; Nagai, Akinori; Maeda, Yukimoto

Proceedings of 1st International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and their Applications (ANIMMA 2009) (USB Flash Drive), 7 Pages, 2009/06

no abstracts in English

Oral presentation

Preparation and evaluation of reference materials (LSD spikes), 2; Evaluation

Sumi, Mika; Takamatsu, Mai*; Ebisawa, Noriyuki; Abe, Katsuo; Kageyama, Tomio; Chiba, Masahiko; Nakazawa, Hiroaki; Suzuki, Toru; Katchi, Tomokazu*; Kushigeta, Yoshiyuki*; et al.

no journal, , 

Standard material which called Large Size Dried (LSD) spikes is required for Plutonium and Uranium measurement by Isotope Dilution Mass Spectrometry (IDMS). Collaboration work between JAEA and JNFL is performed to validate efficient use of standard material (primary) and to evaluate the effectivity of the Pu which separated and purified from MOX stored at JAEA. According to the presentation "Preparation and evaluation of reference materials (LSD spikes) (1) Preparation and testing", uncertainty of the actual sample measurements at Rokkasho Reprocessing plant are evaluated with GUM. Also, the effectivity of the half sized LSD spikes from generally used at JAEA and LSD spikes which prepared from Pu purified from MOX at JAEA are statistically evaluated and validated.

Oral presentation

Preparation and evaluation of reference materials (LSD spikes), 1; Preparation and testing

Katchi, Tomokazu*; Kushigeta, Yoshiyuki*; Murakami, Yoshiki*; Hishi, Tomoyuki*; Ai, Hironobu*; Takamatsu, Mai*; Ebisawa, Noriyuki; Sumi, Mika; Abe, Katsuo; Kageyama, Tomio; et al.

no journal, , 

Standard material which called Large Size Dried (LSD) spikes is required for Plutonium and Uranium measurement by Isotope Dilution Mass Spectrometry (IDMS). Collaboration work between JAEA and JNFL is performed to validate efficient use of standard material (primary) and to evaluate the effectivity of the Pu which separated and purified from MOX stored at JAEA. Preparation of the LSD spikes at JAEA and evaluation with actual samples with remote operation systems at JNFL will be presented.

Oral presentation

Preparation and evaluation of reference materials for accountancy analysis, 1; Preparation and evaluation method

Sumi, Mika; Abe, Katsuo; Kageyama, Tomio; Nakazawa, Hiroaki; Takamatsu, Mai*; Katchi, Tomokazu*; Murakami, Yoshiki*; Ai, Hironobu*

no journal, , 

Isotope dilution mass spectrometry method used for the accountancy analysis at nuclear fuel facilities requires the standard materials called LSD(Large Size Dried) spike. Generally, LSD spikes are prepared from certified reference materials which supplied from foreign countries. However, the difficulty of Pu reference material importation is increasing. It is important for safeguard to attain and continue highly reliable accountancy analysis and stable securing of LSD spike is essential. Therefore, under collaboration work between JAEA and JNFL, several types of LSD spike were prepared. Measurement experiments with actual samples were performed and those results were compared with the results obtained using LSD spike which supplied from foreign laboratory. This report presents preparation of LSD spikes, determination of value of plutonium which separated and purified from MOX and used as raw material, practical test and evaluation method of uncertainty based on ISO-GUM.

Oral presentation

Preparation and evaluation of reference materials for accountancy analysis, 2; Evaluation results

Sumi, Mika; Abe, Katsuo; Kageyama, Tomio; Nakazawa, Hiroaki; Takamatsu, Mai*; Katchi, Tomokazu*; Murakami, Yoshiki*; Ai, Hironobu*

no journal, , 

Destructive analysis for accountancy at nuclear fuel facilities should attain international target values for measurement uncertainties in safeguarding nuclear materials (ITVs).Since measurement uncertainties of isotope dilution mass spectrometry depend on uncertainties of standard materials (spikes) used, utilizing highly reliable standard material is essential. The LSD spikes prepared under collaboration work with JAEA and JNFL has different Pu/U ratio and smaller nuclear material in a spike compared with the LSD spikes used at safeguard laboratories, and the value of Pu which separated and purified from MOX and used as raw material for one of the LSD spike prepared at JAEA were measured at JAEA. Uncertainties of the prepared LSD spikes and the measurement results of actual samples with these LSD spikes were evaluated based on ISO-GUM and compared with ITVs.

Oral presentation

Preparation of plutonium standard material and future tasks

Sumi, Mika; Takamatsu, Mai*; Abe, Katsuo; Kageyama, Tomio; Nakazawa, Hiroaki

no journal, , 

All accountancy analyses at Plutonium Fuel Development Center (PFDC) are performed by isotope dilution mass spectrometry (IDMS) which well-characterized standard materials are required. Since there are no suppliers in Japan, all Pu CRMs are imported while difficulties of Pu transportation are increasing. It is required to secure reference materials for continuing reliable accountancy analysis. Recently, several examinations and tasting were performed at PFDC to save CRMs. Also, Pu was separated and purified from MOX powder (MOX-Pu) stored at PFDC and its potential as standard material has been evaluated. Make up value of MOX-Pu and prepared spikes will be validated by intercomparison including international laboratories.

Oral presentation

Restoration work for obstacle and upper core structure in reactor vessel of experimental fast reactor Joyo

Sekine, Takashi; Ashida, Takashi; Imaizumi, Kazuyuki; Takamatsu, Misao; Nagai, Akinori; Maeda, Yukimoto

no journal, , 

Restoration works for restart of the experimental fast reactor Joyo need to retrieve the bent irradiation test subassembly (MARICO-2) left in the in-vessel storage rack and replace the damaged upper core structure (UCS). In-vessel visual observations using radiation resistant fiberscopes and cameras were conducted to investigate the MARICO-2 and the MARICO-2 was temporarily lifted to confirm the condition. The in-vessel $$gamma$$ ray dose rate was measured to evaluate the activation of the UCS which will be reflected to optimize the shielding design of a UCS replacement cask and a MARICO-2 handling tool.

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