244Cm is a very important nuclide due to the high specific heat release and it may become reasonable to recycle the spent nuclear fuel to extract this isotope. In this work, the dynamics of 244Cm isotope production for the fuel assembly of the WWER-1200 reactor with an enrichment of 4.95% and burnup up to 70 MW · day/kg was calculated using Serpent Monte Carlo code. A similar calculations was performed for MOX-based fuel assembly with the same irradiation characteristics. It has been shown that production of 244Cm in high burnup uranium dioxide fuel, and especially in MOX fuel, reaches a high value, which can cause problems during spent fuel management. The main problems associated with the curium relates to the residual heat and neutron activity.

Current work is aimed at the analysis of the fission products decay influence during fuel reloading, when calculating the accumulated fission products activity for the VVER-1200 reactor fuel campaign. The Bateman problem solution based technique was used for calculations, within the framework of the two fissile nuclides approximation. The fission products producing process for the VVER-1200 reactor stationary campaign is considered, taking into account the reactor shutdown periods for refueling and without taking them into account (instant reload approximation). It was shown, that the instant reload approximation for fission products activity calculations gives the similar accurate result, as calculations with taking into account the shutdown periods. The results can be used to significantly simplify the calculations of fission product activity accumulation in nuclear power reactors.

Analytic methods for nuclear reactor physics problems are still of current interest. They allow the physical interpretation to be obtained for studied processes within simple mathematical apparatus. This work proposes a new approach of neutron and neutronbreeding medium interaction process description based on birth-and-death model. This approach was named the physical birth-and-death model. The equations for the main kinetic characteristic are presented and reactivity values are estimated for two subcritical nuclear assemblies: MASURCA and KUCA.

Results are presented from calculating the neutron radiation of spent nuclear fuel (SNF) from stationary campaigns of VVER-1000 and VVER-1200 reactors due to spontaneous fission and (α, n) reactions. An analytical dependence is obtained for the average number of neutrons produced in spent nuclear fuel per α-particle on the particle’s energy. The neutron radiation of VVER-1200 spent nuclear fuel is several times higher than that of a VVER-1000 reactor, due primarily to the increased number of 244Cm isotopes produced in high-burnup fuel.

The average magnitudes of random values and their dispersions are for many processes known in science and engineering estimated by choosing the appropriate probabilistic processes. The instantaneous intensities of a process are then simulated. At the same time, mathematical expectations of random values and their dispersions can often be exactly or approximately presented in the form of analytical functions of translational intensities. This is a rather common approach, so it is evident that it can also be used in describing processes that occur during the interaction between neutrons and neutron-multiplying media in power reactors of various types. In this work, the above problem is solved for a thermal nuclear reactor.

The experiment-calculated method for separation of total alpha-activities of plutonium isotopes A(Pu-239+Pu-240) on partial activities A(Pu-239) and A(Pu-240) in emergency fallout of Chernobyl accident origin is developed.

Two calculation methods of the total content of Sr-90 and fuel particles of the Chernobyl radionuclide fallout in soil of the 30-km zone of the Chernobyl NPP in Ukraine on the basis of direct and inverse density of soil contamination ratios of Cs-137 and Sr-90 axe presented. It had been determined that the total content of fuel radionuclides in fallouts estimated by both methods differed about two times. Calculation disparity of content of fuel particles is the consequence of arithmetic average and harmonic average inequality. It was shown that the estimation of the total content of fuel particles in emergency fallout of about 1.5% was obtained due to harmonic means.

The possibility of determining the total α activity A(239,240Pu) of 239Pu + 240Pu according to the γ radiation of 103Ru and 106Ru is examined. The statistical properties of the experimental ratios of the activities ρ = A(106Ru)/A(103Ru) are investigated. The distribution of the experimental ratios is similar to the theoretical ratios for fuel and close to a Gaussian distribution with average value 〈p〉 = 0.22 and standard deviation Δ ∼ 0.06. This ratio is used to obtain a relation for estimating A(239,240Pu) from the γ activity A(103Ru). A theoretical analysis is made of the experimental data for the southern raions of Gomel oblast. It is shown that given a good statistical sample of measurements of the γ activity of 103Ru it is possible to estimate the average value of the γ activity A(239,240Pu) and with probability 0.95 the interval of the possible values of this activity.