Vol 120, No 6 (2016)

Information is presented on the status of next generation codes for a new technological platform for nuclear power based on fast reactors and fuel cycle closure. The composition of the system of next generation codes and information on the status of individual codes are presented. The approaches to verification and validation of the codes as well as the collective development of software are described.

The particularities of the formation of the potential biological danger of actinides and fission products in time and the influence of the migration factor on it are examined. The calculation of the dose characteristics of long-lived radionuclides took account of the effect of internal and external irradiation on humans. The internal irradiation dose was calculated taking account of the transfer of radionuclides from soil into food products. It was found that the actinides, ⁹⁰Sr and ¹³⁷C, make the main contribution to the biological danger for 500 years, and are followed by americium and ⁹⁹Tc from the fission products. The separation of 99% of the americium and technetium (which can be transmuted) from the irradiated fuel is optimal for satisfying the principle of radiation equivalence. The use of nitride fuel in fast reactors requires special attention to isolation of ¹⁴C from the environment. It was shown that taking account of the presence of agricultural lands in the action zone of enterprises in the pilot demonstration power complex softens the requirements of admissible carbon emission in the gas phase with absolute satisfaction of the safety requirements for the effect on the general public.

Computational studies of experimentally validated method of solid-phase oxidation of alkali metals in application to the decommissioning of the BR-10 research reactor are presented. Computational-theoretical studies were performed for the method where alkali metals are mixed with oxidizers (granulated slag from copper smelting operations) by pumping alkali metal along a down pipe beneath a layer slag into the reaction chamber.

Methods of calculating the temperature regime and stress-strain state of fuel elements in a sodium-cooled BN-600 are presented. Deformation effects and the local azimuthal temperature distribution of fuel elements with wire winding spacing in fuel assemblies are taken into account. The influence of radiation effects on the temperature regime and stress-state of the fuel elements is shown. The maximum stresses are observed in the section with maximum shape change. At run completion, as a result of nonuniform swelling of the cladding material, on the inner fiber of the cladding the compression stresses transform into tensile stresses and repeat the character of the temperature distribution along the cladding perimeter. The maximum inelastic accumulated strains (ε_c = 1.5%) occur at the point of greatest swelling and high tangential stress.

A three-dimensional code for calculating the dissemination of radioactive contamination in the presence of industrial buildings is being developed at IBRAE RAN. The irradiation dose near an object, including the dose from a radioactive cloud, is calculated on the basis of modeling. The calculation is conducted taking account of radiation screening by buildings. This work is devoted to the verification of the computational method. Calculations of two tests are presented: with and without a screening obstacle. It is concluded that the accuracy of the method, incorporated into the three-dimensional computational code, is adequate.

For known neutron value function, the equation of a nonstationary process in a reactor can be put into a form that is identical to the point-kinetic equation. On this basis, a method is proposed for simultaneously determining the reactivity and neutron value functionals directly from kinetic measurements; this makes it possible to correctly account for spatial effects theoretically. A transient process with strong deformation of the neutron flux in a planar reactor is examined. In neutron flux monitoring using a system of point detectors, the proposed procedure evaluates the reactivity to within 5%; according to the indications of individual detectors, the reactivity was found to be 0.8–6 times its true value.