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and additive in the most conservative concentration distributionOkuno, Hiroshi; Sato, Shohei; Sakai, Tomohiro*; Uchiyama, Gunzo
Journal of Nuclear Science and Technology, 45(11), p.1108 - 1115, 2008/11
Times Cited Count：2 Percentile：16.95(Nuclear Science & Technology)For nuclear criticality safety evaluation of blenders at the mixed uranium-plutonium oxide (MOX) fuel plant, non-uniformity distributions of powders in three chemical components, i.e., MOX, uranium-dioxide (UO) and zinc-stearate, which is a fuel additive, should be taken into account. The model blender considered in this article contained a mixture of 33 wt% PuO-enriched MOX, depleted UO and zinc-stearate in a shape of an upside-down truncated cone, which was surrounded by 30 cm-thick polyethylene. For a limitation of the number of calculation cases, the fissile plutonium mass of the mixture was fixed to 98 kg, and the total concentration of MOX and UO was fixed to 4.0 g/cm
. The most conservative fuel distribution in the aspect of nuclear criticality safety under these constraints was calculated with a two-dimensional optimum fuel distribution code OPT-TWO, so that the importance distribution of MOX and that of zinc-stearate should be individually flattened by conserving the mass of each component. The OPT-TWO calculation was followed by criticality calculation performed with the MCNP code to obtain the neutron multiplication factor of the fuel in the optimum fuel distribution. The most conservative fuel distribution obtained in this research was typically depicted as a shell of zinc-stearate embedded into the central MOX region surrounded by the peripheral UO region. An increase in the neutron multiplication factor was found 25% at most; non-uniformity of plutonium enrichment concentration and that of zinc-stearate concentration contributed to it in almost equal and independent ways.
Sato, Shohei; Sakai, Tomohiro*; Okuno, Hiroshi
JAEA-Data/Code 2007-017, 40 Pages, 2007/08
JAEA-Data-Code-2007-017.pdf:4.8MB
OPT-TWO is a calculation code which calculates the optimum concentration distribution, i.e., the most conservative concentration distribution in the aspect of nuclear criticality safety, of MOX (mixed uranium and plutonium oxide) fuels in the two-dimensional system. To achieve the optimum concentration distribution, we apply the principle of flattened fuel importance distribution with which the fuel system has the highest reactivity. Based on this principle, OPT-TWO takes the following 3 calculation steps iteratively to achieve the optimum concentration distribution with flattened fuel importance: (1) the forward and adjoint neutron fluxes, and the neutron multiplication factor, with TWOTRAN code which is a two-dimensional neutron transport code based on the SN method, (2) the fuel importance, and (3) the quantity of the transferring fuel. In OPT-TWO, the components of MOX fuel are MOX powder, uranium dioxide powder and additive. This report describes the content of the calculation, the computational method, and the installation method of the OPT-TWO, and also describes the application method of the criticality calculation of OPT-TWO.
Okuno, Hiroshi; Sakai, Tomohiro*
Nuclear Technology, 140(3), p.255 - 265, 2002/12
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)In order to facilitate discussions based on quantitative analysis about the end effect, which is often talked about in connection to burnup credit in criticality safety evaluation of spent fuel, we introduced in this paper a burnup importance function. This function shows the burnup effect on the reactivity as a function of the fuel position; an explicit expression of this function was derived according to the perturbation theory. The burnup importance function was applied to the Phase IIA benchmark model that was adopted by the OECD/NEA Expert Group on Burnup Credit Criticality Safety. The function clearly displayed that burnup importance of the end regions increases (1) as burnup, (2) as cooling time, (3) in consideration of burnup profile, and (4) in consideration of fission products.
Okuno, Hiroshi; Tonoike, Kotaro; Sakai, Tomohiro*
Proceedings of International Conference on the New Frontiers of Nuclear Technology; Reactor Physics, Safety and High-Performance Computing (PHYSOR 2002) (CD-ROM), 8 Pages, 2002/10
As the burnup proceeds, reactivity of fuel assemblies for light water reactors decreases by depletion of fissile nuclides, especially in the axially central region. In order to describe the importance of the end regions to the reactivity change, a burnup importance function was introduced as a weighting function to a local burnup variation contributed to a reactivity decrease. The function was applied to the OECD/NEA/BUC Phase II-A model and a simplified Phase II-C model. The application to Phase II-A model clearly showed that burnup importance of the end regions increases as burnup and/or cooling time increases. Comparison of the burnup importance function for different initial enrichments was examined. The application result to the simplified Phase II-C model showed that the burnup importance function was helpful to find the most reactive fuel burnup distribution under the conditions that the average fuel burnup was kept constant and the variations in the fuel burnup were within the maximum and minimum measured values.
; Suyama, Kenya; *
Journal of Nuclear Science and Technology, 35(3), p.240 - 242, 1998/03
Times Cited Count：1 Percentile：15.05(Nuclear Science & Technology)no abstracts in English
; *
Nuclear Technology, 122(3), p.265 - 275, 1998/00
Times Cited Count：2 Percentile：24.46(Nuclear Science & Technology)no abstracts in English
; *
Proc. of PATRAM'98, 1, p.217 - 223, 1998/00
no abstracts in English
*; Komuro, Yuichi; Arakawa, Takuya*
JAERI-Data/Code 97-004, 46 Pages, 1997/03
JAERI-Data-Code-97-004.pdf:1.11MB
no abstracts in English
Okuno, Hiroshi; *
Criticality Safety Challenges in the Next Decade, 0, p.150 - 155, 1997/00
no abstracts in English
Komuro, Yuichi; *
JAERI-Data/Code 96-002, 73 Pages, 1996/02
JAERI-Data-Code-96-002.pdf:2.65MB
no abstracts in English
Okuno, Hiroshi; *
PHYSOR 96: Int. Conf. on the Physics of Reactors, 4, p.L74 - L82, 1996/00
no abstracts in English
Komuro, Yuichi; Naito, Yoshitaka; Kurosawa, Masayoshi; *; *
JAERI-M 94-018, 32 Pages, 1994/03
no abstracts in English
Komuro, Yuichi; Okuno, Hiroshi; Naito, Yoshitaka; *; Nagai, Masakatsu*; *; *; *
JAERI-M 93-190, 94 Pages, 1993/10
no abstracts in English
; Miyoshi, Yoshinori; *; *; *
Journal of Nuclear Science and Technology, 30(5), p.465 - 476, 1993/05
Times Cited Count：6 Percentile：55.97(Nuclear Science & Technology)no abstracts in English
; Miyoshi, Yoshinori; *; *; *
Nuclear Technology, 102, p.125 - 136, 1993/04
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)no abstracts in English
Okuno, Hiroshi; *; *
JAERI-M 92-192, 105 Pages, 1992/12
no abstracts in English
Komuro, Yuichi; Okuno, Hiroshi; Naito, Yoshitaka; *; *; *
JAERI-M 90-126, 125 Pages, 1990/08
no abstracts in English
*; ; *
JAERI-M 88-162, 74 Pages, 1988/08
no abstracts in English
*; Naito, Yoshitaka; Komuro, Yuichi
JAERI-M 88-160, 37 Pages, 1988/08
no abstracts in English
fuel rod on the criticality*; Naito, Yoshitaka; Komuro, Yuichi
JAERI-M 88-159, 18 Pages, 1988/08
no abstracts in English
