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Journal Articles

Proliferation resistance and safeguardability of very high temperature reactor

Shiba, Tomooki; Tomikawa, Hirofumi; Hori, Masato

Proceedings of IAEA Symposium on International Safeguards; Building Future Safeguards Capabilities (Internet), 6 Pages, 2018/11

Journal Articles

A Simple method to create gamma-ray-source spectrum for passive gamma technique

Shiba, Tomooki; Maeda, Shigetaka; Sagara, Hiroshi*; Ishimi, Akihiro; Tomikawa, Hirofumi

Energy Procedia, 131, p.250 - 257, 2017/12

 Times Cited Count:0 Percentile:0.03

In the present paper, the $$gamma$$ ray source data was developed for the debris composition based on "best estimates", and the subsequent photon transportation calculation was performed to evaluate the leakage $$gamma$$ ray spectra according to the fuel debris. Since the creation of the line spectrum source requires a great deal, we have developed the relatively simple but accurate enough method to build up $$gamma$$ ray source, coupling of baseline spectra evaluated by ORIGEN2 code and several line spectra of interest. One of the advantages of the method is taking bremsstrahlung X rays into consideration by utilizing the bremsstrahlung libraries of ORIGEN2. The new $$gamma$$ ray source was used to calculate the detector response of HPGe detector and the results was compared as a benchmark with experimental measurement results of irradiated fuel pins. As the result, the simulated $$gamma$$ ray spectrum shape agreed well with the shape of $$gamma$$ ray spectrum obtained by the experiment.

Journal Articles

Characterization study of four candidate technologies for nuclear material quantification in fuel debris at Fukushima Daiichi Nuclear Power Station

Nagatani, Taketeru; Komeda, Masao; Shiba, Tomooki; Nauchi, Yasushi*; Maeda, Makoto; Sagara, Hiroshi*; Kosuge, Yoshihiro*; Kureta, Masatoshi; Tomikawa, Hirofumi; Okumura, Keisuke; et al.

Energy Procedia, 131, p.258 - 263, 2017/12

 Times Cited Count:3 Percentile:92.06

Journal Articles

Characterization study of four candidate technologies for nuclear material quantification in fuel debris at Fukushima Daiichi Nuclear Power Station, 3; Numerical simulation of passive gamma technique

Shiba, Tomooki; Sagara, Hiroshi*; Tomikawa, Hirofumi

Proceedings of International Nuclear Fuel Cycle Conference (GLOBAL 2017) (USB Flash Drive), 3 Pages, 2017/09

Since the removal of fuel debris from the Fukushima Daiichi Nuclear Power Plant is planned to commence in 2021, measurement technologies for quantification of the nuclear material in fuel debris will be required for appropriate nuclear material management. In this paper, an outline of a passive gamma technique as one of the measurement technologies is briefly described, and the results of phase 1 and 2 of the so-called common set of simulation models for fuel debris and canisters are reported. The newly developed coupling method is applied to produce a gamma ray source for simulation. As the result of phase 1, it is revealed that the variation in the composition of fuel debris does not affect the gamma ray leakage behavior from canisters. According to the result of phase 2, the primary peak of Eu-154 at 1.27 MeV is clearly observable, although the debris is centrally located in canister. In addition, rotational scanning is effective for correcting the deviation in detection efficiency due to debris located off-center in canisters.

Journal Articles

Applicability evaluation of candidate technologies for nuclear material quantification in fuel debris at Fukushima Daiichi Nuclear Power Station; Passive gamma technique

Shiba, Tomooki; Tomikawa, Hirofumi; Sagara, Hiroshi*; Ishimi, Akihiro

57th Annual Meeting of the Institute of Nuclear Materials Management (INMM 2016), Vol.1, p.365 - 374, 2017/02

Fission products (FPs) such as Ce and Eu seem to be very low volatile even in high temperature environment in the severe accident of nuclear reactors. They are supposed to chemically coexist with nuclear fuel. In our passive gamma ray spectroscopy, gamma rays from such FPs are measured and their amount and burnup are estimated. Then we multiply the mass ratio of the FPs and nuclear materials, and we obtain the mass of nuclear material of interest. According to hypothetical fuel debris and canister models, we performed simulation of leakage gamma rays from canister of debris. gamma ray source spectra were derived from the composition of the hypothetical fuel debris and the photon transport calculation was carried out. In addition, we conducted experiments of gamma ray measurement from intact spent fuels irradiated in the Experimental Fast Reactor Joyo in order to validate the prediction performance of the simulation by the comparison of the experiments and simulation.

Journal Articles

Characterization study of four candidate technologies for nuclear material quantification in fuel debris at Fukushima Daiichi Nuclear Power Station (Interim report)

Nagatani, Taketeru; Komeda, Masao; Shiba, Tomooki; Maeda, Makoto; Nauchi, Yasushi*; Sagara, Hiroshi*; Kosuge, Yoshihiro*; Kureta, Masatoshi; Tomikawa, Hirofumi; Okumura, Keisuke; et al.

Proceedings of INMM 57th Annual Meeting (Internet), 10 Pages, 2016/07

Journal Articles

Passive gamma spectrometry of low-volatile FPs for accountancy of special nuclear material in molten core material of Fukushima Daiichi Nuclear Power Plant; Evaluation of detector response from various hypothetical fuel canister

Shiba, Tomooki; Sagara, Hiroshi*; Tomikawa, Hirofumi

56th Annual Meeting of the Institute of Nuclear Materials Management (INMM 2015), Vol.3, p.1735 - 1741, 2016/00

In response to the accident at Fukushima Daiichi Nuclear Power Station, passive gamma spectrometry is being researched and developed as one of the candidates of a mass measurement method for the special nuclear materials in molten core material. Among Fission Products (FPs) accompanied in molten core materials, some of them are very low-volatile and emit high-energy gamma rays, which enable us to derive the mass of those FPs by passive gamma spectrometry. Using the mass ratio of the FPs and nuclear materials, this technique provides the mass estimation of nuclear materials. This technique is relatively simple and was applied to the analysis of nuclear materials in the clean-up process of damaged Three Mile Island unit-2 (TMI-2) reactor. In this paper, we show the characteristics of leakage gamma rays from removed fuel canisters simulated by MCNP. Different detector responses to gamma rays from fuel debris are also evaluated supposing NaI, LaBr$$_{3}$$ and HPGe.

Journal Articles

Effect of radial zoning of $$^{241}$$Am content on homogenization of denatured Pu with broad range of neutron energy based on U irradiation test in the experimental fast reactor Joyo

Shiba, Tomooki*; Sagara, Hiroshi*; Onishi, Takashi; Koyama, Shinichi; Maeda, Shigetaka; Han, C. Y.*; Saito, Masaki*

Annals of Nuclear Energy, 51, p.74 - 80, 2013/01

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

The design consideration of DU-Am oxide fuel pin was performed for Pu denaturing in the framework of the protected plutonium production based on the irradiation analyses of the depleted U (DU) samples irradiated in the environment of broad range of neutron energy in the experimental fast reactor Joyo. From the results of irradiation analyses of DU, it was confirmed that there is a strong dependence of transmutation behavior of DU on the resonance neutron ratio even in a fast reactor. Also, it was confirmed that there is a strong effect of sample material form and shape on generated Pu nuclide inventory especially near the reflector area ($$>$$20% resonance neutron ratio), because of the intensive self-shielding of $$^{238}$$U, though less is expected for $$^{241}$$Am. Sensitivity study of hypothetical DU-Am oxide fuel pellet irradiation on neutron energy and burn-up was performed to evaluate significant gradient of radial $$^{238}$$Pu isotopic composition profile (e.g., from 12 to 18% distribution in 3% Am doping, in 30% resonance neutron ratio and in 4.0$$times$$10$$^{22}$$ [n/cm$$^{2}$$] of neutron fluence inside a large pellet with softened neutron spectrum), and vulnerability of the fuel pellet surface in terms of Pu denaturing was revealed. Design consideration of radial zoning of $$^{241}$$Am content was introduced to flatten the radial distribution of isotopic composition of Pu. The results of radial zoning of $$^{241}$$Am (4% and 3% of Am in the outer and inner zone of DU-Am oxide fuel pellet) in hypothetical irradiation neutronics analysis showed the radial profile of produced Pu is over 15 at.% of $$^{238}$$Pu isotopic composition in any zone and meets the criteria of Kimura et al. based on decay heat of Pu to impede utilization to fission explosive devices.

Journal Articles

Protected plutonium production at fast breeder reactor blanket; Chemical analysis of uranium-238 samples irradiated in experimental fast reactor Joyo

Onishi, Takashi; Koyama, Shinichi; Shiba, Tomooki*; Sagara, Hiroshi*; Saito, Masaki*

Progress in Nuclear Energy, 57, p.125 - 129, 2012/05

 Times Cited Count:1 Percentile:11.68(Nuclear Science & Technology)

In order to develop blanket fuel with high proliferation resistance in fast breeder reactor, chemical analysis of nine $$^{238}$$U samples irradiated in experimental fast reactor Joyo and Pu contents and Pu isotopic composition of the samples were measured. As results, dependence of Pu production behavior from $$^{238}$$U on neutron spectra was revealed.

Oral presentation

Blanket fuel with high proliferation resistance in fast breeder reactor, 8; Experimental analysis of irradiated Am sample in JOYO, 1

Onishi, Takashi; Sudo, Mitsuo; Koyama, Shinichi; Tanaka, Kenya; Sekioka, Ken*; Shiba, Tomooki*; Sagara, Hiroshi*; Saito, Masaki*

no journal, , 

In order to develop the high proliferation resistance fuel for fast breeder reactor, plutonium production/incineration behavior of americium samples irradiated in fast reactor "JOYO" was evaluated.

Oral presentation

Research for Am-based proliferation resistance

Shiba, Tomooki*; Sagara, Hiroshi*; Saito, Masaki*; Koyama, Shinichi; Maeda, Shigetaka

no journal, , 

In order to design for FBR blanket fuel with high proliferation resistance, transmutation behavior of Am-containing depleted uranium under fast neutron environment is evaluated by computer simulation as a parameter of the Am content. Produced plutonium having high proliferation resistance are reduced with decreasing neutron energy in the case of Joyo irradiation condition.

Oral presentation

Blanket fuel with high proliferation resistance in fast breeder reactor, 9; Experimental analysis of irradiated U sample in JOYO, 3

Onishi, Takashi; Sudo, Mitsuo; Koyama, Shinichi; Sekioka, Ken*; Shiba, Tomooki*; Sagara, Hiroshi*; Saito, Masaki*

no journal, , 

In order to develop blanket fuel with high proliferation resistance in fast breeder reactor, production and incineration behavior of Pu in U samples irradiated in fast experimental reactor JOYO were evaluated.

Oral presentation

Blanket fuel with high proliferation resistance in fast breeder reactor, 10; Theoretical analysis of irradiated samples in JOYO, 4

Shiba, Tomooki*; Sagara, Hiroshi*; Saito, Masaki*; Onishi, Takashi; Koyama, Shinichi; Maeda, Shigetaka

no journal, , 

In order to develop blanket fuel with high proliferation resistance in fast breeder reactor, production and incineration behavior of Pu in U samples irradiated in fast experimental reactor JOYO were evaluated by calculation. Results of sample irradiation loaded at different axial position were compared and dependence of transmutation behavior on neutron energy spectra were evaluated.

Oral presentation

Blanket fuel with high proliferation resistance in fast breeder reactor, 11; Prediction of P$$^{3}$$ mechanism inside pellet

Sagara, Hiroshi*; Shiba, Tomooki*; Saito, Masaki*; Onishi, Takashi; Koyama, Shinichi; Maeda, Shigetaka

no journal, , 

In order to develop blanket fuel with high proliferation resistance in fast breeder reactor, virtual irradiation behavior of Am-U pellets at different position in fast experimental reactor JOYO were analyzed. By detail calculation in pellets, rim effects in U-Am pellet irradiation were evaluated and feasibility of results of sample irradiation were investigated.

Oral presentation

Blanket fuel with high proliferation resistance in fast breeder reactor, 15; Prediction of irradiation behavior of DU-Am pellets

Shiba, Tomooki*; Sagara, Hiroshi*; Han, C. Y.*; Saito, Masaki*; Onishi, Takashi; Koyama, Shinichi; Maeda, Shigetaka

no journal, , 

The design consideration of hypothetical depleted U and Am (DU-Am) oxide fuel pin was performed to produce Pu with high proliferation resistance in fast breeder reactors. As a result, DU-Am oxide fuel pellet with large diameter under epithermal neutron spectrum is desirable for the production of denatured Pu.

Oral presentation

Passive $$gamma$$ spectrometry of low-volatile FPs for accountancy of special nuclear material in molten core material of Fukushima Daiichi Nuclear Power Plant; Numerical simulation of leakage $$gamma$$-ray from molten core materials in hypothetical canister

Sagara, Hiroshi*; Shiba, Tomooki*; Tomikawa, Hirofumi; Ishimi, Akihiro; Hori, Keiichiro; Saito, Masaki*

no journal, , 

For the nuclear material accountancy of molten core material in Fukushima Daiichi Unit 1, 2 and 3 (1F1, 1F2 and 1F3), feasibility studies of variety of technologies are being performed. As one of the technologies, feasibility study of passive $$gamma$$ spectroscopy of low-volatile FPs for nuclear material accountancy in molten core material has been performed with reviewing TMI-2 experience, and the correlation of actinides and FPs inventory in core of 1F1, 1F2 and 1F3, considering the sensitivity of axial neutron spectrum, void, burnup, enrichment distribution unique to BWR fuel, and also leakage $$gamma$$-ray from molten core materials sphere model. In the present paper, numerical simulation of leakage $$gamma$$-ray from molten core materials in hypothetical canister is dealt for determination of radioactivity of low-volatile high-energy emission FPs, which could be utilized for nuclear material quantity estimation.

Oral presentation

Passive $$gamma$$ spectrometry of low-volatile FPs for accountancy of special nuclear material in molten core material of Fukushima Daiichi Nuclear Power Plant; Detectability of leakage $$gamma$$-ray and fundamental characteristics of U-Ce/Eu compound

Tomikawa, Hirofumi; Sagara, Hiroshi*; Shiba, Tomooki*; Ishimi, Akihiro; Osaka, Masahiko; Watahiki, Masaru; Kuno, Yusuke

no journal, , 

For nuclear material accountancy of molten core material in Fukushima Daiichi Nuclear Power Station units 1, 2 and 3 (1F1, 1F2 and 1F3), a variety of technologies are being evaluated from the viewpoint of applicability for in-situ measurement. For one of the technologies, a feasibility study of passive $$gamma$$ spectroscopy of low-volatile fission products (FPs) has been performed by reviewing TMI-2 experience, and studying the correlation of actinides and FPs inventory in the cores of 1F1, 1F2 and 1F3, considering the sensitivity of axial neutron spectrum, void, burnup, enrichment distribution unique to BWR fuel, and leakage $$gamma$$-ray from molten core materials sphere model. In this paper, numerical simulation of leakage $$gamma$$-ray from molten core materials in a hypothetical canister is dealt with for determination of radioactivity of low-volatile high-energy emission FPs, which could be utilized for special nuclear material (SNM) quantity estimation coupled with SNM/FPs ratio derived from core inventory calculations. This paper also presents the summary of survey results of high-temperature chemical stability of lanthanides coexisting with nuclear material in a certain atmospheres and temperatures simulating severe accident.

Oral presentation

Current status of accompanying FP passive $$gamma$$ measurement to special nuclear material quantification in fuel debris

Shiba, Tomooki; Sagara, Hiroshi*; Hiyama, Toru; Tomikawa, Hirofumi

no journal, , 

In response to the accident at Fukushima Daiichi Nuclear Power Station, passive $$gamma$$ spectrometry has been researched and developed as one of the candidates of a mass measurement method of the special nuclear materials in molten core material. Among Fission Products (FPs) accompanied in molten core materials, some of them are very low-volatile and emit high-energy $$gamma$$ rays which enable to derive the mass of those FPs by passive $$gamma$$ spectrometry. Using the mass ratio between the FPs and nuclear materials, this technique provides the mass estimation of nuclear materials. This technique is relatively simple and was applied to the analysis of nuclear materials in the clean-up process of damaged Three Mile Island unit-2 (TMI-2) reactor. In the poster, we show the outlines of the project, the analytical and experimental results conducted until now, and the future plan of the project.

Oral presentation

Characterization study of candidate technologies for nuclear material quantification in fuel debris at Fukushima Daiichi Nuclear Power Station, 1; General outline

Nagatani, Taketeru; Komeda, Masao; Shiba, Tomooki; Maeda, Makoto; Nauchi, Yasushi*; Sagara, Hiroshi*; Kureta, Masatoshi; Tomikawa, Hirofumi; Okumura, Keisuke; Heinberg, C.; et al.

no journal, , 

no abstracts in English

38 (Records 1-20 displayed on this page)