Authors & Affiliations
Kizub P.A., Mitenkova E.F.
Nuclear Safety Institute of the Russian Academy of Sciences, Moscow, Russia
Mitenkova E.F. – Cand. Sci. (Phys.-Math.), Head of the Neutronic Calculations Laboratory, Nuclear Safety Institute of Russian Academy of Sciences.
The stability and correctness of neutron source have a special significance in criticality calculations using Monte Carlo methods. In such calculations the correctness of local calculated characteristics, such as neutron reaction rates, directly depends from the steady-state neutron source.
The fission rate and neutron source distributions are considered for systems with dominance ratio close to one, such as loosely coupled systems. For Pin-cell Array with Irradiated Fuel (OECD/NEA benchmark) the stable asymmetric neutron source distributions are obtained. For this system the possibility of obtaining a symmetric distribution is demonstrated using weight windows in MCNP5 code.
For loosely coupled systems is shown that in calculations even with large statistics when providing sustainable neutron source it is still possible obtain incorrect effective neutron multiplication factor. The lowered multiplication factor is obtained for different initial neutron source distributions with 100000 neutrons per generation for non symmetric loosely coupled systems with unequal enrichment in symmetric zones. In these calculations the neutron source distribution remains persistent but is not correct.
The calculations have been performed using the TDMCC and MCNP5 codes.
Monte Carlo calculations, loosely coupled systems, neutron source, effective neutron multiplication factor, fission rate, weight windows method
1. Whitesides G.E. A Difficulty in Computing the k-effective of the World. Transactions of the American Nuclear Society, 1971, vol. 14, pp. 680.
2. Brown F.B."K-effective of the World" and Other Concerns for Monte Carlo Eigenvalue Calculations. Progress in Nuclear Science and Technology, 2011, vol. 2, pp. 738–742.
3. Kizub P.A., Mitenkova E.F. Istochnik neytronov deleniya v raschetakh metodom Monte-Karlo dlya slabosvyazannykh sistem [Neutron source for loosely-coupled systems in Monte-Carlo criticality calculation]. Preprint IBRAE-IBRAE-2015-02 - PreprintNSI RAS -IBRAE-2015-02. Moscow, 2015.
4. Dufek J. Accelerated Monte Carlo Eigenvalue Calculations. Proc. XIII Meeting on Reactor Physics Calculations in the Nordic Countries. Sweden, 2007.
5. Blomquist R., Nouri A., Amirshaw M. et al. OECD/NEA source convergence benchmark program: overview and summary of results. Proc. 7th Int. Conf. on Nuclear Criticality Safety. Tokai, Japan, 2003, vol. 1, pp. 278-282.
6. Lee M.J., Joo H.G., Lee D. et al. Investigation of CMFD Accelerated Monte Carlo Eigenvalue Calculation with Simplified Low Dimensional Multigroup Formulation. Proc. PHYSOR-2010. Pittsburgh, USA, 2010.
7. Blomquist R., Amirshaw M., Hanlon D. et al. Source Convergence in Criticality Safety Analysis, Phase I: Results of Four Test Problems. OECD NEA, 2006, no. 5431.
8. Mitenkova E.F., Koltashev D.A., Kizub P.A. Raspredelenie skorosti reaktsii deleniya v slabosvyazannoy sisteme dlya testovoy modeli "shakhmatnaya doska" [The Distribution of Fission Reaction Rate in a Weakly Coupled System for Testing the Checkerboard Model]. Atomnaya energiya – Atomic Energy, 2014, vol. 116, no. 6, pp. 345-349.
9. Kizub P.A., Mitenkova E.F. Osobennosti raspredeleniya skorosti deleniya v slabosvyazannykh sistemakh v raschetakh metodom Monte-Karlo [Features of the velocity distribution division in loosely coupled systems in calculations Monte Carlo]. Voprosy Atomnoy Nauki i Tekhniki. Seriya: Yaderno-reaktornye konstanty – Problems of Atomic Science and Technology. Series: Nuclear and Reactor Constans, 2015, no. 1, pp. 41-46. Available at: http://vant.ippe.ru/year2015/1/993-5.html (accessed 15.02.2017).
10. Kizub P.A., Mitenkova E.F. Istochniki deleniya v raschetakh metodom Monte-Karlo na kritichnost' slabosvyazannykh sistem [Sources division in the calculation of the Monte Carlo method on criticality of loosely coupled systems]. Voprosy Atomnoy Nauki i Tekhniki. Seriya: Yaderno-reaktornye konstanty – Problems of Atomic Science and Technology. Series: Nuclear and Reactor Constans, 2016 (in Russian, unpublished).
11. X-5 Monte Carlo Team. MCNP - A General Monte Carlo N-Particle Transport Code, version 5, April 2003.
12. Programma: TDMCC (Time-Dependent Monte Carlo Code) [Program: TDMCC (Time-Dependent Monte Carlo Code)]. Certificate of state. Registration ?2010614412. "RFNC VNIIEF".
13. Mitenkova E.F., Semenova T.V. Ispol'zovanie programmy TDMCC dlya resheniya zadach s dominantnym otnosheniem, blizkim k edinitse [Using TDMCC program for solving problems with a dominant attitude, close to unity]. VANT. Series: matematicheskoe modelirovanie fizicheskih processov- PAST. Series: mathematical modeling of physical processes, 2015, no. 4, pp. 3-14.
14. Ueki T., Brown F.B. Informatics Approach to Stationary Diagnostics of the Monte Carlo Fission Sources Distribution. Transactions of the American Nuclear Society, 2003, vol. 89, pp. 458.
15. Brown F.B. On the use of Shannon Entropy of the fission distribution for assessing convergence of Monte Carlo criticality calculations. Proc. PHYSOR-2006. Vancouver, BC, Canada, 2006.