TRU oxide sample reactivity worths measured in the FCA-IX assemblies with systematically changed neutron energy spectra

Fukushima, Masahiro; Okajima, Shigeaki*; Mukaiyama, Takehiko*

Journal of Nuclear Science and Technology, 20 Pages, 2023/00

https://doi.org/10.1080/00223131.2023.2240872

A series of integral experiments was conducted to evaluate the fission and the capture cross- sections of transuranic (TRU) nuclides at the fast critical facility FCA of the Japan Atomic Energy Agency (JAEA). The experiments were carried out using seven uranium-fueled assemblies of the FCA. The neutron energy spectra of the core regions were adjusted so as to change from an intermediate neutron spectrum to a fast neutron spectrum on an assembly-by-assembly basis. The integral data measured with these experimental configurations provide some neutron energy characteristics: 1) fission rate ratios (FRRs) of Np, Pu, Pu, Am, Am, and Cm relative to Pu by using absolutely calibrated fission chambers, 2) small sample reactivity worths (SRWs) of Np, Pu, Pu, Am, and Am where oxide powders of around 15 to 20 grams were used, 3) criticalities, and 4) spectral indices such as fission rate ratios of U relative to U. In this paper, details of the SRW measurements are reported, and the latest Japanese Evaluated Nuclear Data Library JENDL-5 is tested by using the integral data obtained in systematically varied neutron energy spectra.

Systematic measurements and analyses for lead void reactivity worth in a plutonium core and two uranium cores with different enrichments

Fukushima, Masahiro; Goda, J.*; Oizumi, Akito; Bounds, J.*; Cutler, T.*; Grove, T.*; Hayes, D.*; Hutchinson, J.*; McKenzie, G.*; McSpaden, A.*; et al.

Nuclear Science and Engineering, 194(2), p.138 - 153, 2020/02

https://doi.org/10.1080/00295639.2019.1663089

To validate lead (Pb) nuclear cross sections, a series of integral experiments to measure lead void reactivity worth was conducted systematically in three fast spectra with different fuel compositions on the Comet critical assembly of the National Criticality Experiments Research Center. Previous experiments in a high-enriched uranium (HEU)/Pb and a low-enriched uranium (LEU)/Pb systems had been performed in 2016 and 2017, respectively. A follow-on experiment in a plutonium (Pu)/Pb system has been completed. The Pu/Pb system was constructed using lead plates and weapons grade plutonium plates that had been used in the Zero Power Physics Reactor (ZPPR) of Argonne National Laboratory until the 1990s. Furthermore, the HEU/Pb system was re-examined on the Comet critical assembly installed newly with a device that can guarantee the gap reproducibility with a higher accuracy and precision, and then the experimental data was re evaluated. Using the lead void reactivity worth measured in these three cores with different fuel compositions, the latest nuclear data libraries, JENDL 4.0 and ENDF/B VIII.0, were tested with the Monte Carlo calculation code MCNP version 6.1. As a result, the calculations by ENDF/B-VIII.0 were confirmed to agree with lead void reactivity worth measured in all the cores. It was furthermore found that the calculations by JENDL 4.0 overestimate by more than 20% for the Pu/Pb core while being in good agreements for the HEU/Pb and LEU/Pb cores.

A Simple and practical correction technique for reactivity worth of short-sized samples measured by critical-water-level method

Kitamura, Yasunori*; Fukushima, Masahiro

Nuclear Science and Engineering, 186(2), p.168 - 179, 2017/05

https://doi.org/10.1080/00295639.2016.1273017

An inconsistency between the reactivity worth of short-size samples measured by the critical-water-level (CWL) method and that conventionally analysed for validating the nuclear data and the nuclear calculation methods has been known. The present study investigated this inconsistency in terms of a simple theoretical framework and proposed a simple and practical technique for correcting the measured sample reactivity worth without making supplementary experiments. A series of Monte Carlo calculations that simulated typical sample reactivity worth measurement by the CWL method showed that this inconsistency is effectively reduced by the present correction technique.

Characteristic test of initial HTTR core

Nojiri, Naoki; Shimakawa, Satoshi; Fujimoto, Nozomu; Goto, Minoru

Nuclear Engineering and Design, 233(1-3), p.283 - 290, 2004/10

https://doi.org/10.1016/j.nucengdes.2004.08.015

This paper describes the results of core physics test in start-up and power-up of the HTTR. The tests were conducted in order to ensure performance and safety of the high temperature gas cooled reactor, and was carried out to measure the critical approach, the excess reactivity, the shutdown margin, the control rod worth, the reactivity coefficient, the neutron flux distribution and the power distribution. The expected core performance and the required reactor safety characteristics were verified from the results of measurements and calculations.

Preliminary analyses for HTTR's start-up physics tests by HTTR nuclear characteristics evaluation code system

Fujimoto, Nozomu; Nojiri, Naoki; Nakano, Masaaki*; Takeuchi, Mitsuo; Fujisaki, Shingo; Yamashita, Kiyonobu

JAERI-Tech 98-021, 66 Pages, 1998/06

JAERI-Tech-98-021.pdf:2.63MB

no abstracts in English

Measurement of reactivity worths of Sm,Cs,Gd,Nd,Rh,Eu,B and Er aqueous solution samples

Komuro, Yuichi; Suzaki, Takenori; *; Sakurai, Kiyoshi; Horiki, Oichiro*

JAERI-Research 97-088, 19 Pages, 1997/11

JAERI-Research-97-088.pdf:0.86MB

no abstracts in English

High temperature Doppler effect experiment for U at FCA, I; Reactivity worth measurement with a small heated sample up to 1500C

Okajima, Shigeaki; Oigawa, Hiroyuki; Mukaiyama, Takehiko; Ando, Masaki

Journal of Nuclear Science and Technology, 33(3), p.202 - 210, 1996/03

https://doi.org/10.3327/jnst.33.202

no abstracts in English

Doppler effect measurement up to 2,000C in the fast critical facility FCA

Okajima, Shigeaki; Oigawa, Hiroyuki; Ando, Masaki; Mukaiyama, Takehiko

Proc. of 9th Int. Symp. on Reactor Dosimetry, 0, p.172 - 179, 1996/00

no abstracts in English

Measurement of effective delayed neutron fraction of VHTRC-1 core

Akino, Fujiyoshi; Takeuchi, Motoyoshi; Ono, Toshihiko

Journal of Nuclear Science and Technology, 31(8), p.861 - 863, 1994/08

https://doi.org/10.3327/jnst.31.861

no abstracts in English

Neutronics properties of JMTR LEU core

Nagaoka, Yoshiharu; Saito, Minoru;

Transactions of the American Nuclear Society, 66, p.454 - 455, 1992/11

no abstracts in English