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JAEA Reports

Calculation of nuclear core parameters for HTTR; Report of summer holiday practical training 2021

Isogawa, Hiroki*; Naoi, Motomasa*; Yamasaki, Seiji*; Ho, H. Q.; Katayama, Kazunari*; Matsuura, Hideaki*; Fujimoto, Nozomu*; Ishitsuka, Etsuo

JAEA-Technology 2022-015, 18 Pages, 2022/07

JAEA-Technology-2022-015.pdf:1.37MB

As a summer holiday practical training 2021, the impact of 10 years long-term shutdown on critical control rod position of the HTTR and the delayed neutron fraction ( $_{rm eff}$ ) of the VHTRC-1 core were investigated using Monte-Carlo MVP code. As a result, a long-term shutdown of 10 years caused the critical control rods of the HTTR to withdraw about 4.00.8 cm compared to 3.9 cm in the experiment. The change in critical control rods position of the HTTR is due to the change of some fission products such as $^{241}$ Pu, $^{241}$ Am, $^{147}$ Pm, $^{147}$ Sm, $^{155}$ Gd. Regarding the $_{rm eff}$ calculation of the VHTRC-1 core, the $_{rm eff}$ value is underestimate of about 10% in comparison with the experiment value.

Journal Articles

Calculation of transient parameters of the integral kinetic model with delayed neutrons for space-dependent kinetic analysis of coupled reactors

Takezawa, Hiroki*; Tuya, D.; Obara, Toru*

Nuclear Science and Engineering, 195(11), p.1236 - 1246, 2021/11

https://doi.org/10.1080/00295639.2021.1920797

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

This study introduces new methodologies for integrating fission reactions induced by delayed neutrons into the Multi-Region Integral Kinetic (MIK) code by using a Monte Carlo neutron transport calculation. First, it was confirmed that it is feasible to solve the Integral Kinetic Model (IKM) with delayed neutrons by the forward Euler discretization method in terms of the number of time steps. This can be done with the help of the law of radioactive decay to reflect the delay in the emission of delayed neutrons in the discretized IKM. Second, a new Monte Carlo-based methodology was introduced for calculating the cumulative distribution functions of secondary fission induced by prompt and delayed neutrons. These functions are necessary for the discretized IKM. The results of preliminary verification using the Godiva reactor confirmed the applicability of the new Monte Carlo-based methodology.

Journal Articles

Evaluation of high-energy delayed gamma-ray spectra dependence on interrogation timing patterns

Rodriguez, D.; Bogucarska, T.*; Koizumi, Mitsuo; Lee, H.-J.; Pedersen, B.*; Rossi, F.; Takahashi, Tone; Varasano, G.*

Nuclear Instruments and Methods in Physics Research A, 997, p.165146_1 - 165146_13, 2021/05

https://doi.org/10.1016/j.nima.2021.165146

Times Cited Count：2 Percentile：32.77(Instruments & Instrumentation)

Journal Articles

Utilizing PUNITA experiments to evaluate fundamental delayed gamma-ray spectroscopy interrogation requirements for nuclear safeguards

Rodriguez, D.; Koizumi, Mitsuo; Rossi, F.; Seya, Michio; Takahashi, Tone; Bogucarska, T.*; Crochemore, J.-M.*; Pedersen, B.*; Takamine, Jun

Journal of Nuclear Science and Technology, 57(8), p.975 - 988, 2020/08

https://doi.org/10.1080/00223131.2020.1742812

Times Cited Count：4 Percentile：43.68(Nuclear Science & Technology)

Journal Articles

Model design of a compact delayed gamma-ray moderator system using $^{252}$ Cf for safeguards verification measurements

Rodriguez, D.; Rossi, F.; Takahashi, Tone; Seya, Michio; Koizumi, Mitsuo

Applied Radiation and Isotopes, 148, p.114 - 125, 2019/06

https://doi.org/10.1016/j.apradiso.2019.01.002

Times Cited Count：5 Percentile：47.59(Chemistry, Inorganic & Nuclear)

Journal Articles

Sensitivity and uncertainty analysis of $beta_{rm eff}$ for MYRRHA using a Monte Carlo technique

Iwamoto, Hiroki; Stankovskiy, A.*; Fiorito, L.*; Van den Eynde, G.*

EPJ Nuclear Sciences & Technologies (Internet), 4, p.42_1 - 42_7, 2018/11

https://doi.org/10.1051/epjn/2018023

This paper presents a nuclear data sensitivity and uncertainty analysis of the effective delayed neutron fraction $beta_{rm eff}$ for critical and subcritical cores of the MYRRHA reactor using the continuous-energy Monte Carlo transport code MCNP. The $beta_{rm eff}$ sensitivities are calculated by the modified -ratio method proposed by Chiba. Comparing the $beta_{rm eff}$ sensitivities obtained with different scaling factors introduced by Chiba shows that a value of is the most suitable for the uncertainty quantification of $beta_{rm eff}$ . Using the calculated $beta_{rm eff}$ sensitivities and the JENDL-4.0u covariance data, the $beta_{rm eff}$ uncertainties for the critical and subcritical cores are determined to be 2.2 0.2% and 2.0 0.2%, respectively, which are dominated by delayed neutron yield of $^{239}$ Pu and $^{238}$ U.

Journal Articles

Delayed gamma-ray spectroscopy, 2; Design study of moderator for a practical system

Rossi, F.; Rodriguez, D.; Takahashi, Tone; Seya, Michio; Koizumi, Mitsuo

Nihon Kaku Busshitsu Kanri Gakkai Dai-39-Kai Nenji Taikai Rombunshu (CD-ROM), 3 Pages, 2018/11

This paper (presentation) reports on the design study for seeking compactness of moderator (and reflector) structure for the Delayed Gamma-ray Spectroscopy Non Destructive Assay system to be applied for verification of fissile isotopic (Pu-239, Pu-241 and U-235) composition ratio in High Radioactive Nuclear Material sample such as dissolved solution of reprocessing facility. We first investigated advantages and disadvantages of using different compact neutron sources as DT and DD neutron generators. This led us to the conclusion of using DD sources to achieve a compact (and practical) NDA system. Based on MCNP simulations, with the use of a DD neutron generator, a preliminary optimization study was performed and will be shown here.

Journal Articles

Assessment of human body surface and internal dose estimations in criticality accidents based on experimental and computational simulations

Sono, Hiroki; Ono, Akio*; Kojima, Takuji; Takahashi, Fumiaki; Yamane, Yoshihiro*

Journal of Nuclear Science and Technology, 43(3), p.276 - 284, 2006/03

https://doi.org/10.3327/jnst.43.276

Times Cited Count：1 Percentile：9.91(Nuclear Science & Technology)

For a study on the applicability of a personal dosimetry method to criticality accident dosimetry, an assessment of the human body surface and internal dose estimations was performed by experimental and computational simulations. The experimental simulation was carried out in a criticality accident situation at the TRACY facility. The neutron and -ray absorbed doses in muscle tissue were separately estimated by a dosimeter set of an alanine dosimeter and a thermoluminescence dosimeter made of enriched lithium tetra borate with a phantom. The computational simulation was conducted with a Monte Carlo code taking account of dose components of neutrons, prompt -rays and delayed -rays. The computational simulation was ascertained to be valid by comparison between the calculated dose distributions in the phantom and the measured ones. The assessment based on the experimental and computational simulations confirmed that the personal dosimetry using the dosimeter set provided a first estimation of the body surface and internal doses with precision.

Journal Articles

Kinetic parameter $beta_{rm eff}/ell$ measurement on low enriched uranyl nitrate solution with single unit cores (600, 280T, 800) of STACY

Tonoike, Kotaro; Miyoshi, Yoshinori; Kikuchi, Tsukasa*; Yamamoto, Toshihiro

Journal of Nuclear Science and Technology, 39(11), p.1227 - 1236, 2002/11

https://doi.org/10.3327/jnst.39.1227

Times Cited Count：21 Percentile：77.24(Nuclear Science & Technology)

Kinetic parameter $beta_{rm eff}/ell$ of low enriched uranyl nitrate solution was measured by the pulsed neutron source method in the STACY. This measurement was repeated systematically over several uranium concentrations from 193.7 gU/ to 432.1 gU/. Used core tanks were two cylindrical tanks whose diameters are 600 mm and 800 mm and one slab tank which has 280 mm thickness and 700 mm width. In this report, experimental data such as solution conditions, critical solution level for each solution condition, subcritical solution levels where measurements were conducted, measured decay time constants of prompt neutron and extrapolated $beta_{rm eff}/ell$ values are described as well as basic principle of the pulsed neutron source method. $beta_{rm eff}/ell$ values were evaluated also by computation with the diffusion code CITATION in SRAC and the nuclear data library JENDL 3.2. Both experimental and computational $beta_{rm eff}/ell$ values show good agreement.

Journal Articles

Adjustment of total delayed neutron yields of $^{235}$ U, $^{238}$ U and $^{239}$ Pu by using results of in-pile measurements of effective delayed neutron fraction

Sakurai, Takeshi; Okajima, Shigeaki

Proceedings of International Conference on the New Frontiers of Nuclear Technology; Reactor Physics, Safety and High-Performance Computing (PHYSOR 2002) (CD-ROM), 12 Pages, 2002/10

The cross section adjustment method was applied to total delayed neutron yields of $^{235}$ U, $^{238}$ U and $^{239}$ Pu of the JENDL-3.2 file by using experimental results of effective delayed neutron fraction $beta_{eff}$ at six cores built in two fast critical facilities of the MASURCA and FCA and a thermal critical facility of the TCA to improve these yields. The adjustment was carried out on the yields given at several incident neutron energy points in the file. Furthermore, to validate these adjusted delayed neutron yields, analyses were performed for the $beta_{eff}$ experiments at ZPR fast critical facility. These adjusted yields brought a reduction of uncertainty of calculated $beta_{eff}$ and an improvement in agreement of $beta_{eff}$ between experiment and calculation.

Journal Articles

Evaluation of Delayed Neutron Data for JENDL-3.3

Yoshida, Tadashi*; Okajima, Shigeaki; Sakurai, Takeshi; Nakajima, Ken; Yamane, Tsuyoshi; Katakura, Junichi; Tahara, Yoshihisa*; Zukeran, Atsushi*; Oyamatsu, Kazuhiro*; Osawa, Takaaki*; et al.

Journal of Nuclear Science and Technology, 39(Suppl.2), p.136 - 139, 2002/08

http://wwwndc.jaea.go.jp/nd2001/proc/pdf/1_0136.pdf

no abstracts in English

Journal Articles

Adjustment of total delayed neutron yields of $^{235}$ U, $^{238}$ U and $^{239}$ Pu in JENDL-3.2 using benchmark experiments on effective delayed neutron fraction $beta_{eff}$

Sakurai, Takeshi; Okajima, Shigeaki

Journal of Nuclear Science and Technology, 39(1), p.19 - 30, 2002/01

https://doi.org/10.3327/jnst.39.19

Times Cited Count：6 Percentile：39.3(Nuclear Science & Technology)

The cross section adjustment method was applied to total delayed neutron yields of $^{235}$ U, $^{238}$ U and $^{239}$ Pu of the JENDL-3.2 file by using experimental results of effective delayed neutron fraction $beta_{eff}$ at six cores built in two fast critical facilities of the MASURCA and FCA and a thermal critical facility of the TCA to improve these yields. The adjustment was carried out on the yields given at several incident neutron energy points in the file. After the adjustment, the yield of $^{238}$ U was almost uniformly decreased by about 3% below 7 MeV. The yield of $^{239}$ Pu was increased by 2.6% and that of $^{235}$ U was decreased by 0.9% at the thermal energy point, while the change of yield was less than 0.3% at the other energy points for these nuclides. By using these adjusted yields, the uncertainty of calculated $beta_{eff}$ was reduced and the agreement of $beta_{eff}$ between experiment and calculation was improved.

Journal Articles