This paper presents the calculation results of the set of test problems for a research reactor with a tube-type low enriched uranium (LEU, 19.7 w/o, U-9%Mo) fuel and oxide high enriched uranium (HEU, 90 w/o) fuel, a light water moderator, and a beryllium reflector. The static cases and the depletion problem were examined. Calculations were performed using continuous energy Monte Carlo codes: MCNP (+MCREB for burnup calculation), MCU-PTR, and SERPENT 2. The impact of the cross-section libraries used for a particular problem on the calculated results was investigated.

No abstract

No abstract

No abstract

The special features in comparing the computational neutron-physical characteristics with experiment and the applications of the computational data in operating a research reactor are examined. Specifically, the interaction of the calculation with operational procedures, in particular, with the procedure for calibrating the working organs of the safety and control system, is examined.The basic rated neutron-physical characteristics for operating a research reactor are determined by two methods: experimentally and computationally. The present paper compares the results obtained by these methods. An attempt is made to formulate the requirements for a computational simulation and for experimental procedures which will make it possible to use these two methods together effectively.Computational Model of IRT. The Moscow Engineering-Physics Institute has developed and employs the computer program TIGRIS for computational support of the operation of IRT [1]. This program is used to calculate the neutronphysical characteristics of the stationary state of the core, taking account of fuel burnup, 135 Xe accumulation, and poisoning of beryllium (formation of 6 Li and 3 He in the beryllium reflector).In spite of the possibilities of the computational technology and the existence of high-precision computer programs, at the present time engineering programs (as a rule, small-group diffusion models) are, once again, used for certain problems. Specifically, this concerns the operational computations: determination of the intergral reactivity characteristics (reactivity excess, effectiveness of the working organs of the safety and control system), and the fuel burnup of research reactors. The uncertainties in the initial data and the errors in the experimental data, with which the computational results are compared, can result in a discrepancy which is much greater than the computational error of the high-precision computer programs. In addition, IRT has certain features which make it difficult to use the high-precision programs: there are no loads which are comprised completely of fresh fuel and there is no typical load at the start of a run. The core-averaged fuel burnup at the start of a run ranges from 20 to 40%. Consequently, it is impossible to rule out an error due to the uncertainty in the burnup which is due to the error in the measurement of the thermal power. We also note that fuel assemblies operate for approximately 5 yr. Consequently, to calculate the burnup of a specific fuel assembly using high-precision programs it is important to simulate at least a 5-yr history of reactor operation. For the same reasons, it is impossible to prescribe uniquely all initial data and perform high-precision calculation of the present state of a reactor without having any information on burnup, obtained previously using engineering programs.The TIGRIS program has been verified by comparing with the operational experimental data on IRT at the Moscow Engineering-Physics Institute. Essentially, the integrated characteristics of the reac...