Monte Carlo N-Particle eXtended (MCNPX) simulation for passive neutron measurement of fuel debris at Fukushima Daiichi Nuclear Power Plants

Nagatani, Taketeru; Nakajima, Shinji; Kosuge, Yoshihiro*; Shiromo, Hideo; Asano, Takashi

Proceedings of INMM 55th Annual Meeting (Internet), 10 Pages, 2014/07

Meltdown of the reactor cores of Units 1-3 occurred at Fukushima Daiichi Nuclear Power Plants (1F). Fuel debris at 1F contains minor actinides and fission products and neutron absorber. These materials make it difficult to quantify fertile nuclear materials in fuel debris by the conventional passive neutron technique. We consider that DDSI and PNAR which focused on fissile material are promising techniques to quantify the nuclear materials in the fuel debris. A concept of application of these techniques to fuel debris measurement was investigated and presented at the last INMM annual meeting. In order to evaluate the applicability of these techniques to fuel debris measurement, we investigated the neutron behavior in the fuel debris by using MCNPX simulation code. Because property of fuel debris is not clear, source term data used were prepared by referring TMI data. This paper provides results of MCNPX simulation for fuel debris measurement at 1F with passive neutron techniques.

Developments of a LaBr scintillation detector system for neutron resonance densitometry (NRD)

Koizumi, Mitsuo; Tsuchiya, Harufumi; Kitatani, Fumito; Harada, Hideo; Takamine, Jun; Kureta, Masatoshi; Seya, Michio; Kimura, Atsushi; Iimura, Hideki; Becker, B.*; et al.

Proceedings of INMM 55th Annual Meeting (Internet), 7 Pages, 2014/07

Progress and future prospects of nuclear forensics technology development project at JAEA

Kimura, Yoshiki; Shinohara, Nobuo; Sato, Kaneaki; Toda, Nobufumi; Shinoda, Yoshiharu; Funatake, Yoshio; Watahiki, Masaru; Kuno, Yusuke

Proceedings of INMM 55th Annual Meeting (Internet), 7 Pages, 2014/07

In 2010, the Japan Government issued the national statement at Nuclear Security Summit (Washington D.C., USA) to develop technologies related to measurement and detection of nuclear materials for nuclear forensics within three-year timeframe, and to share the products with the international community in order to contribute to strengthening the nuclear security system. In response to this statement, JAEA that possesses sufficient technical capabilities to fulfil this nuclear forensics mission has started a nuclear forensics technology development project since JFY 2011. This paper will present the progress of the development project during JFY 2011 to 2013. This project includes the developments of analytical technologies such as isotope and impurity measurements, morphology analysis, age determination technique, and the prototype of national nuclear forensics library (NNFL). Some future prospects of this project will be also presented in this paper.

Quantitative comparison study on nuclear nonproliferation for plutonium in spent fuel direct disposal and recycle use

Kuno, Yusuke; Hara, Daisuke*

Proceedings of INMM 55th Annual Meeting (Internet), 9 Pages, 2014/07

Comparison study of material-oriented Proliferation Resistance (PR) for plutonium in spent fuels resulting from both cases of direct disposal and recycle use is quantitatively made. The extended the figure-of-merit (FOM) described in term of time was used, where dose of actual spent fuels and their chemical/physical properties, and material quantity are additionally considered to the original FOM. This case study on spent fuels from LWR, once/twice recycles with MOX-LWR and Fast Reactor showed significant differences on FOM (attractiveness) among them.

Development and demonstration of a Pu NDA system using ZnS/BO ceramic scintillator detectors

Nakamura, Hironobu; Ozu, Akira; Kobayashi, Nozomi*; Mukai, Yasunobu; Sakasai, Kaoru; Nakamura, Tatsuya; Soyama, Kazuhiko; Kureta, Masatoshi; Kurita, Tsutomu; Seya, Michio

Proceedings of INMM 55th Annual Meeting (Internet), 9 Pages, 2014/07

To establish an alternative technique of He-3 neutron detector that is used for nuclear material accountancy and safeguards, we have started an R&D project to develop a new type of neutron detector (Pu NDA system) using ZnS/BO ceramic scintillator with support of Japanese government. The design of the alternative system (ASAS: Alternative Sample Assay System) is basically referenced from INVS (INVentory Sample assay system) which is passive neutron assay system of plutonium and has total 18 He-3 tubes (about 42% of counting efficiency), and the small amount of Pu in the MOX powder or Pu nitrate solution in a vial can be measured. In order to establish the technology and performance after the fabrication of the new detector progresses, we are planning to conduct demonstration activity in the early 2015 experimentally. The demonstration activity implements the confirmation of reproducibility about sample positioning, optimization of detector parameters, counting statistical uncertainty, stability (temperature and -ray change) check and figure of merit (FOM) using check source and actual MOX powder. In addition to that, performance comparison between current INVS and the ASAS are also conducted. In this paper, we present some analytical study results using a Monte-Carlo simulation code (MCNP), entire ASAS design and demonstration plan to prove technology and performance.

Design and implementation of B+He integrated continuous monitor (BHCM) to holdup monitoring in glove boxes

Mukai, Yasunobu; LaFleur, A. M.*; Nakamura, Hironobu; Menlove, H. O.*; Swinhoe, M. T.*; Marlow, J. B.*; Kurita, Tsutomu

Proceedings of INMM 55th Annual Meeting (Internet), 8 Pages, 2014/07

In order to improve the safeguards and nuclear material accountancy of holdup measurements and establish an alternative technology for He shortage, we have designed the B + He Integrated Continuous Monitor (BHCM) and implemented the measurements to continuously monitor the holup in gloveboxes at Plutonium Conversion Developoment Facility. In this paper, we present the outline of BHCM, the comparison between MCNP simulations and the measured results in preliminaly test and a demonstration of process monitoring ability during operation to see the relation between Totals trend and operational status by using B detection tubes.

Improvement of INVS measurement uncertainty for Pu and U-Pu nitrate solution

Makino, Risa; Swinhoe, M. T.*; Suzuki, Yoshimasa; Mukai, Yasunobu; Menlove, H. O.*; Marlow, J. B.*; Nakamura, Hironobu

Proceedings of INMM 55th Annual Meeting (Internet), 9 Pages, 2014/07

The Inventory Verification Sample systems (INVS) is a non-destructive assay (NDA) system for small inventory samples to quantify the Pu amount in Pu and U-Pu nitrate solutions and MOX powder with 31.3% counting efficiency (for Cf). It has been used for IAEA safeguards measurement for many years at the Plutonium Conversion Development Facility (PCDF) for the samples taken at the time of Random Interim Inspection (RII) and Physical Inventory Verification (PIV), and is currently used as partial defects verification equipment with uncertainty about 35% accuracy for solution samples. The INVS is a inline detector therefore it is very convenient to use since it can be used for a sample inside the glove box without bag-out. If the measurement uncertainty can be improved (to 1%), it is expected that the usage can be extended to the operator's own measurements in MC&A to reduce effort and the number of destructive analyses (DA). In order to improve the measurement uncertainty, we have performed multiplicity measurements using a variety of solution samples (concentration, acidity and volume) to determine the Pu amount and uncertainty, although the multiplicity analysis is challenging. To control the measurement quality, a few MOX ceramic fuel pellets with known Pu amount are used. The results are evaluated by three kinds of methods (calibration curve, known- and multiplicity) to determine the best measurement method. In the range of concentration of typical samples, we could confirm good correlations between measured doubles and Pu effective mass in the three methods. Especially, the conventional calibration curve method showed a good performance with short measurement time and small uncertainty when the calibration standards were a good match to the unknown samples. In this paper, we present the INVS system design and measurement results with uncertainty using solution samples and comparison results among the three calibration methods.