Calculation of six-group importance weighted delayed neutron fractions and prompt neutron lifetime of MTR research reactors based on Monte Carlo method

• Kinetic parameters of a typical MTR research reactor are calculated based on MCNIC method.
• MCNIC method is applied to such a nuclear experimental facility of an existing MTR research reactor.
• The results are compared with 1/υ1/υ poisoning, k-ratio, perturbation, and ZPRN methods as standard techniques.
• The impact of cross section libraries on calculation of kinetic parameters in thermal systems is investigated.

The accurate estimation of effective delayed neutron fraction and prompt neutron lifetime are of major concerns in safety analysis of nuclear reactors. In this paper, Tehran Research Reactor (TRR) is taken as a case study of MTR research reactors and kinetic parameters of the facility are estimated utilizing Monte Carlo Neutron Importance Calculation (MCNIC) method. The results are compared with 1/υ1/υ poisoning, k-ratio, perturbation, and zero power reactor noise (ZPRN) methods. Taking perturbation results as reference information, the percent error in effective delayed neutron fraction calculated by MCNIC, k-ratio, and ZPRN methods are −3.7, −6.8, and 1.7 respectively. These results for ℓp parameter calculated by MCNIC, 1/υ poisoning, and ZPRN methods are 2.9, 5.7, and 6.4 respectively. A good agreement is seen among different methods of estimation. Note that error originated from cross section library is a different source of error which is also discussed in the text. As MCNIC method considers the problem in a more realistic manner, considering neutron importance in calculations, this method is more reliable than the other methods. A quantitative and qualitative discussion is given in the paper to indicate the advantages and disadvantages of each method for the case study in TRR.