Том 123, № 4 (2018)

The current status of the nuclear database used for engineering calculations in the field of nuclear energy is reported. It is shown that the nuclear database and its attendant computational methods, stabilization, and transmission to the next generation of specialists who will have to solve the problems of the future development of nuclear power must be improved and updated.

An accident with ‘rupture of steam line’ as the initial event was studied for a reactor facility with VVER-1000. A computational analysis was performed of different flow scenarios of an accident with singular and multiple failures of the safety systems. The realization probability and the consequences were evaluated for each accident sequence. The consequences of the accidents are ranked and the most instructive combinations of failures of systems and blockings are determined from the standpoint of risk. The presented method is based on multivariate calculations and an integrated combination of deterministic and probabilistic approaches to safety validation.

The dependence of dimensional changes occurring in the structural parts made of E-635 zirconium alloy on the metallurgical and operational factors as a result of thermal creep, radiation growth, and radiation creep was studied. Tests close to operating conditions showed high resistance to radiation growth and thermal and radiation creep of the structural parts of VVER-1000 fuel assemblies made of E-635 zirconium alloy. Parts with greater resistance to creep without irradiation also possess high resistance to creep in the presence of irradiation. However, in-reactor creep can be almost 10 times greater than creep with no irradiation.

Thermodynamic calculations of the interaction of gaseous uranium hexafluoride and ammonia were performed. Possible mechanisms for the recovery of uranium hexafluoride are examined. It is shown that the uranium in this system will be recovered mainly due to the ammonia proper and not the formed atomic hydrogen as previously believed. The calculations showed that the calorimetric, theoretical, and actual temperature of the interaction reaction of uranium hexafluoride and ammonia is numerically equal to ~0 K, i.e., uranium hexafluoride and ammonia react at any temperature. In application to the Kedr apparatus, it is concluded that the reactor walls must be cooled substantially or a cooling gas must be introduced into the reaction zone in amounts sufficient to compensate the heat of reaction in order to avoid an unpredictable rate of the flame process.

The production of diluent for high-enrichment uranium in a cascade from waste uranium hexafluoride with unknown ²³⁴U content is examined. To secure high-quality diluent and reduce separative work consumption, it is proposed that the diluent be produced in two stages with sorting and extraction of the best intermediate produced in terms of ²³⁴U concentration after the first stage. The worst intermediate products are best used at the second stage to obtain low-enrichment uranium hexafluoride satisfying ASTM C 996-15 specifications. In addition, the obtained new wastes can be used in a third stage to produce diluent with low ²³⁴U concentration.

Computational and design studies of the arrangement of an autonomous power unit with a nuclear reaction in a sparsely populated location characterized by weak soil are presented. A variant of a possible arrangement of the reactor taking account of the requirements of the facility is shown. The radioactive emission around the reactor and the distribution of heat emission in the soil, for picking and determining the number of cooling elements, are calculated. A technical solution that provides for the installation of a nuclear reactor in soft ground is proposed.

The dependence of the spectral power of radiation in the transmission window of air near wavelength 2 mm on the altitude of stratospheric nuclear explosions is investigated. One of the rotational transition lines of nitrogen oxide NO is studied. Calculations of the time dependence of the nitrogen oxide concentration were performed by the method of mathematical modeling of plasma. It is shown that a large amount of nitrogen oxide is formed by explosion γ-rays in the partial-ionization region ahead of the shock wave front; the nitrogen oxide concentration reaches a quasistationary level and remains almost constant for hundreds of microseconds. The quasistationariness is maintained by secondary γ-rays arising in inelastic scattering of explosion neutrons. Estimates of the spectral power of radiation near wavelength 2 mm are obtained. It is shown that at altitude 45 km above the ground the spectral power of the radiation is 10⁵ times greater than for ground-level explosions.