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Journal Articles

Development of in situ stress estimation method based on the measured convergence and geological observations

Kamemura, Katsumi*; Aoyagi, Kazuhei; Nago, Makito*; Sugawara, Kentaro*

Dai-45-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.43 - 48, 2018/01

In situ stress state is very important for the design of deep underground facility of high-level radioactive waste disposal repository. This study establishes a practical and effective method for estimating in situ stress state based on the measured convergence and detailed geological observations during gallery excavation. The convergence was measured in various directions of the loop gallery at 350m depth of the Horonobe URL; this allows determination of the stress state corresponding to the rock mass behavior in 120m $$times$$ 200m area. In situ stress state estimated by the back analysis considering existing faults and fractures showed a good agreement with that of estimated from hydraulic fracturing method.

Journal Articles

A Power spectrum approach to tally convergence in Monte Carlo criticality calculation

Ueki, Taro

Journal of Nuclear Science and Technology, 54(12), p.1310 - 1320, 2017/12

AA2017-0413.pdf:1.05MB

 Times Cited Count:6 Percentile:65.17(Nuclear Science & Technology)

In Monte Carlo criticality calculation, confidence interval estimation is based on the central limit theorem (CLT) for a series of tallies. A fundamental assertion resulting from CLT is the convergence in distribution (CID) of the interpolated standardized time series (ISTS) of tallies. In this work, the spectral analysis of ISTS has been conducted in order to assess the convergence of tallies in terms of CID. Numerical results indicate that the power spectrum of ISTS is equal to the theoretically predicted power spectrum of Brownian motion for effective neutron multiplication factor; on the other hand, the power spectrum of ISTS for local power fluctuates wildly while maintaining the spectral form of fractional Brownian motion. The latter result is the evidence of a case where a series of tallies is away from CID, while the spectral form supports normality assumption on the sample mean.

Journal Articles

Estimation of rock mass stress state based on the convergence measurement result during tunnel excavation

Kamemura, Katsumi*; Aoyagi, Kazuhei; Nago, Makito*; Sugawara, Kentaro*; Matsubara, Makoto*

Dai-14-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (Internet), 6 Pages, 2017/01

In the design of deep underground structures such as high-level radioactive waste disposal repositories, the estimation of rock mass stress state is important as well as the estimation of mechanical characteristics of rock mass. This study establishes a practical and effective method for estimating in situ stress based on the convergence measurement results obtained during gallery construction of URL. The convergence was measured in various directions of the URL loop gallery at 350 m depth, and this will allow determination of the stress state over a large area using a back analysis method. In order to improve the accuracy of initial stress estimation, the relationship between convergence measurement results and geological situation of existing fractures were studied. The analysis results show good agreement with the in situ stress state results reported in previous studies and confirm the applicability of the proposed method.

Journal Articles

Estimation of rock mass stress state based on convergence measurement during gallery excavation

Aoyagi, Kazuhei; Nago, Makito*; Kamemura, Katsumi*; Sugawara, Kentaro*

Proceedings of 9th Asian Rock Mechanics Symposium (ARMS-9) (USB Flash Drive), 10 Pages, 2016/10

Journal Articles

Design and verification of support system for underground excavations under anisotropic stress conditions

Motoshima, Takayuki*; Fujita, Tomo; Aoyagi, Kazuhei; Shirase, Mitsuyasu*; Nago, Makito*

Proceedings of 7th International Symposium on In-situ Rock Stress (RS 2016) (Internet), 9 Pages, 2016/05

Journal Articles

Estimation of initial stress based on the convergence measurement result during tunnel excavation

Kamemura, Katsumi*; Fujita, Tomo; Aoyagi, Kazuhei; Nago, Makito*; Shirase, Mitsuyasu*; Sugawara, Kentaro*

Dai-44-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.109 - 114, 2016/01

How to estimate the initial stress state as well as a mechanical characteristic of rock mass is important in the design of deep underground structures. Some stress measurement methods using borehole, which methodology and evaluation method have been discussed in detail, are carried out if necessary. However, obtained results are often varying widely, so the evaluation of initial stress is difficult. Here, the initial stress state corresponding to the rock mass behavior of about 120m$$times$$200m area is evaluated using the convergence measurement results during tunnel excavation in 350m depth. Analysed result corresponded to that of other method, so the validity of the proposed method was shown.

Journal Articles

Influence of multidimensionality on convergence of sampling in protein simulation

Metsugi. Shoichi

Journal of the Physical Society of Japan, 74(6), p.1865 - 1870, 2005/06

 Times Cited Count:0 Percentile:0.01(Physics, Multidisciplinary)

We study the problem of convergence of sampling in protein simulation originating in the multidimensionality of protein's conformational space. Since several important physical quantities are given by second moments of dynamical variables, we attempt to obtain the time of simulation necessary for their sufficient convergence. We perform a molecular dynamics simulation of a protein and the subsequent principal component (PC) analysis as a function of simulation time T. As T increases, PC vectors with smaller amplitude of variations are identified and their amplitudes are equilibrated before identifying and equilibrating vectors with larger amplitude of variations. This sequential identification and equilibration mechanism makes protein simulation a useful method although it has an intrinsic multidimensional nature.

Journal Articles

Development of fission source acceleration method for slow convergence in criticality analyses by using matrix eigenvector applicable to spent fuel transport cask with axial burnup profile

Kuroishi, Takeshi; Nomura, Yasushi

Journal of Nuclear Science and Technology, 40(6), p.433 - 440, 2003/06

 Times Cited Count:1 Percentile:11.39(Nuclear Science & Technology)

Effective source acceleration method is studied in criticality safety analysis for realistic spent fuel transport cask. Various axial burnup profiles based on in-core flux measurements are proposed in the OECD/NEA/BUC benchmark Phase II-C. In some cases, calculations by ordinary Monte Carlo method show very slow convergence of fission source distribution, and unacceptably large skipped cycles are needed. The matrix eigenvector calculation that has been developed and incorporated in the ordinary Monte Carlo calculation to improve the slow convergence is applied to the benchmark. The efficiency of this method depends on the precision of matrix elements. In a certain stage of insufficient convergence of fission source distribution, especially for this benchmark of very slow convergence, more acceleration procedure causes anomalous results because of large statistical fluctuations of matrix elements corresponding to low source levels. Therefore, we propose effective source acceleration method with less calculation time than increasing histories for the estimation of matrix elements.

JAEA Reports

Analysis of the applicability of acceleration methods for a triangular prism geometry nodal diffusion code

Fujimura, Toichiro*; Okumura, Keisuke

JAERI-Research 2002-024, 27 Pages, 2002/11

JAERI-Research-2002-024.pdf:1.04MB

A prototype version of a diffusion code has been developed to analyze the hexagonal core as reduced moderation reactor and the applicability of some acceleration methods have been investigated to accelerate the convergence of the iterative solution method. The hexagonal core is divided into regular triangular prisms in the three-dimensional code MOSRA-Prism and a polynomial expansion nodal method is applied to approximate the neutron flux distribution by a cubic polynomial. The multi-group diffusion equation is solved iteratively with ordinal inner and outer iterations and the effectiveness of acceleration methods is ascertained by applying an adaptive acceleration method and a neutron source extrapolation method, respectively. The formulation of the polynomial expansion nodal method is outlined in the report and the local and global effectiveness of the acceleration methods is discussed with various sample calculations. A new general expression of vacuum boundary condition, derived in the formulation is also described.

Journal Articles

New acceleration method of source convergence for loosely coupled multi unit system by using matrix K calculation

Kuroishi, Takeshi; Nomura, Yasushi

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

To accelerate the slow convergence of the fission source distribution, the matrix k calculation has been developed and incorporated in the ordinary Monte Carlo method. The acceleration can be performed by the fission source correction using the eigenvector of the fission matrix, if the coupling coefficients are approximately evaluated in the middle of Monte Carlo calculation. In this paper, we propose two effective applications of the matrix k, that is, the acceleration repetition method and the source generation method. The former simply repeats the matrix k calculation, and the result for the irradiated fuel pin cell shows enough effective to accelerate the fission source on the criticality estimation. However, in some cases of the loosely coupled multi unit system, the repetition of matrix k more than twice could not be carried out to get into convergence because of many units of low source level. The latter is newly devised here to apply to such cases. The checkerboard fuel storage rack is one of the typical cases, and the calculated results show the effectiveness of this method.

JAEA Reports

Journal Articles

Three-dimensional thermal stress numerical convergence analysis of a hot spot in a thin pipe using the boundary element method

Bains, R.S.*; Sugimoto, Jun

Engineering Analysis with Boundary Elements, 14, p.267 - 275, 1994/00

 Times Cited Count:4 Percentile:76.68(Engineering, Multidisciplinary)

no abstracts in English

Journal Articles

A Simulation procedure for multicomponent distillation columns incorporating plate efficiencies

*;

J.Chem.Eng.Jpn., 18(1), p.78 - 81, 1985/00

 Times Cited Count:5 Percentile:72.91(Engineering, Chemical)

no abstracts in English

Journal Articles

Effectiveness of an adaptive acceleration method for inner iterations in some neutron diffusion codes

; *

Nuclear Science and Engineering, 77, p.360 - 367, 1981/00

 Times Cited Count:2 Percentile:45.65(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Convergence of solutions of the MHD stability code ERATO

Tsunematsu, Toshihide; ; *; ;

Comput.Phys.Commun., 19(2), p.179 - 183, 1980/00

 Times Cited Count:8 Percentile:61.65(Computer Science, Interdisciplinary Applications)

no abstracts in English

Journal Articles

Application of coarse-mesh rebalance acceleration to Monte Carlo eigenvalue problems

; ; ; ; ; ; ;

Nuclear Science and Engineering, 59(4), p.326 - 336, 1976/04

 Times Cited Count:3

no abstracts in English

JAEA Reports

18 (Records 1-18 displayed on this page)
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