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Np using graphite thermal columnNakamura, Shoji; Endo, Shunsuke; Kimura, Atsushi; Shibahara, Yuji*
KURNS Progress Report 2020, P. 94, 2021/08
The present study selected Np among radioactive nuclides and aimed to converge a contradiction between reported thermal-neutron capture cross sections. Neutron irradiation was carried out using the graphite thermal column equipped with the Kyoto University Research Reactor. A solution equivalent to 950 Bq order of radioactivity was pipetted out of a Np standard solution and dropped onto a fiber filter, which was then dried with an infrared lamp to prepare a Np sample. The Np sample was quantified using 312-keV gamma ray emitted from 
Pa in a radiation equilibrium with Np. To monitor a thermal-neutron flux component at an irradiation position, the Np sample was irradiated together with several stable nuclides as neutron flux monitors: 
Sc, 
Co, 
Mo, 
Ta and 
Au. The reaction rate of Np was obtained from gamma-ray yields given by 
Np and Pa, and then the thermal-neutron capture cross section of Np was derived.
Mineo, Hideaki; Asakura, Toshihide; Hotoku, Shinobu; Ban, Yasutoshi; Morita, Yasuji
Proceedings of GLOBAL2003 Atoms for Prosperity; Updating Eisenhower's Global Vision for Nuclear Energy (CD-ROM), p.1250 - 1255, 2003/11
An advanced aqueous reprocessing process has been proposed for the next generation fuel cycle. Key technologies applied to the process are: removal of I-129, separation of Np and FP(Tc) separation by selective reduction of Np(VI) and high acid scrubbing of Tc within a single cycle process, MA separation by extraction chromatography and Cs/Sr separation. U separation just after dissolution was supposed to be effective to reduce the required capacity of the following extraction step. Among them Np reduction rate in TBP solution was measured, which was found to be lower than that in aqueous solution. Using an improved flow sheet spent fuel test, based on the Np reduction test, was carried out and about 90% of Np was separated before U and Pu partitioning step.
Np and 
AmNakagawa, Tsuneo; Iwamoto, Osamu; Hasegawa, Akira
JAERI-Research 2001-059, 84 Pages, 2002/01
JAERI-Research-2001-059.pdf:4.96MB
no abstracts in English
Nakagawa, Tsuneo; Takano, Hideki; Hasegawa, Akira
NEA/WPEC-8, p.1 - 116, 1999/00
no abstracts in English
*
PNC TJ9601 98-002, 115 Pages, 1998/03
In fuel cycles with recycled actinide, core characteristics are largely influenced by minor actinide (MA: Np, Am), Accurate nuclear data of MA such as fission cross section are required to estimate the effect of MA with high accuracy. In this study, fast neutron induced fission cross section of MA was measured using Dynamitron Accelerator in Tohoku University. New or improved techniques and tools with high precision and fast timing capability were developed for this study. Those are as follows: (1)Development of a sealed fission chamber,(2)Intensification of Li neutron target, (3)Improvement of time-resolution of Time-of-Right (TOF) electronic circuit, (4)Introduction of MA (Np237, Am241 and Am243) samples with large sample mass and (5)Introduction of a U235 sample with high purity. Using these improved tools and samples, fission cross section of Np237 was measured between 10 to 100 keV. On the other hand, averaged fission cross section for Maxwell distribution spectrum with kt=25.3 keV was measured for Am241 and Am243.
Np and Am in sedimentary geological formationTanaka, Tadao; Takebe, Shinichi; Ogawa, Hiromichi; Muraoka, Susumu
JAERI-Research 98-018, 20 Pages, 1998/03
JAERI-Research-98-018.pdf:0.94MB
no abstracts in English
Tanaka, Tadao; Muraoka, Susumu
JAERI-Research 98-017, 20 Pages, 1998/03
JAERI-Research-98-017.pdf:0.91MB
no abstracts in English
*
PNC TJ9604 97-001, 108 Pages, 1997/03
A lead slowing-down spectrometer was installed coupled to the 46 MeV electron linac at Research Reactor Institute, Kyoto university (KURRI). Characteristics of the Kyoto University Lead Slowing-down Spectrometer (KULS) were measured for (1)the relation between neutron slowing-down time t(
s) and energy E (keV) (E=190/t
in Bi hole and E=156/ in Pb hole), (2)energy resolutlon (
40 % in Bi and Pb holes), and (3)neutron energy spectrum by the neutron TOF method. The results obtained by the MCNP code were in general agreement with these experimental ones. The KULS has been applied to the fission cross section measurements of Am-241, Am-243 and Am-242m relative to that of U-235 from 0.1 eV to 10 keV, making use of the back-to-back type double fission chambers. For Am-241, Dabbs and ENDF/B-VI data are in good agreement with the present measurement. The JEND L-3.2 data are smaller by a factor of 2 between 10 and 200 eV. The ENDF/B-VI data for Am-243 are lower between 15 and 60 eV, and the JENDL-3.2 are lower in general above 100 eV. It has been found that the preliminary result for the Am-242m(n,f) reaction is close to the ENDF/B-VI and the JENDL-3.2 data. Thermal neutron cross sections for Am-241 and Am-243 have also been measured in a standard Maxwellian distribution spectrum field. Finally, aiming at the measurement of capture cross section for MA nuclides, the experimental investigation for Np-237 sample (2 mg) has been performed with the KULS. Due to the comparable background counts to the foreground ones, the capture events from the sample have scarecely been detected with an Ar-gas proportional counter.
*
PNC TJ9601 97-001, 51 Pages, 1997/03
In fuel cycles with recycled actinide, core characteristics are largely influenced by minor actinide (MA:Np, Am, Cm). Accurate nuclear data of MA such as fission cross section are required to estimate the effect of MA with high accuracy.In this study fast neutron induced fission cross section of MA is measured using Dynamitron Accelerator in Tohoku University. The experimental method and the samples, which were developed or introduced during the last year, were improved in this fiscal year: (1)Development of a sealed fission chamber, (2)Intensification of Li neutron target, (3)Improvement of time-resolution of Time-of-flight (TOF) electronic circuit, (4)Introduction of Np237 samples with large sample mass and (5)Introduction of a U235 sample with high purity. Using these improved tools and samples, the fission cross section ratio of NP237 relative to U235 was measured between 5 to 100keV, and the fission cross section of Np237 was deduced. On the other hand, samples of Am241 and Am243 were obtained from Japan Atomic Energy Research Institute (JAERI) after investigating fission cross section of two americium isotopes (Am241 and Am243) which are important for core physics calculation of fast reactors.
