Vol 122, No 6 (2017)

The possible reasons for nonstandard embrittlement and significant variance of the experimental data in the study of the impact of neutron irradiation on the properties of reactor vessel materials are analyzed. The authors assume on the basis of experimental data and analysis of foreign research that the fluence dependence of the degree of radiation embrittlement can be of nonmonotonic as well as cyclic. The observation of vibratory processes in the embrittlement kinetics of vessel steel attests periodic transformation of structure and change in the properties of the metal. It is expected that the defect structure formed as a result of neutron bombardment undergoes transformation once or periodically in the direction of losses as well as restoration of the initial properties. The mentioned data shape the search for methods of regulating the radiation resistance of materials.

The initial registration brought to light the characteristics and disposition of wastes that should be disposed of on-site (special radioactive wastes). The criteria for validating the classification of radwastes as special are presented. The established criteria for the origin of wastes and the location of an object and its sanitaryprotective zone do not permit classifying the radwastes of certain large objects as special even though their removal is unjustified both in terms of dose loads and the risk of potential radiation as well as in terms of financial cost. Criteria are proposed for storage sites for special radwastes for inclusion in the developed regulatory documents, regulating their safe operation and transfer to accommodation and storage sites.

The aim of the experiment was to elucidate the formation mechanism of color centers with optical absorption band in the region 660–680 nm, which are induced in KS-4V and KI quartz glasses under irradiation by ⁶⁰Co γ-rays at dose rate 2.5 Gy/sec and temperature 77, 273, and 310 K in the dose range 30–10⁵ Gy. The 665 nm band is induced efficiently in KI samples, which contain more metallic impurities (<10 ppm). It is shown that the 665 nm band induced in KS-4V after soaking at 300 K for 40 min diminishes by approximately 30% and almost vanishes after 3 h; it is thermally stable at <300 K and is completely annealed at ≥323 K. The accumulation kinetics of color centers of the 665 nm band in KS-4V at >4·10² Gy is caused by rupture of the M⁺O–Si≡ bond near aluminum ≡Al³⁺. In contrast to KS-4 and KI glasses, KU-1 glass is recommended for small windows in the ITR reactor for the visible part of the spectrum.

It is shown that together with the reduced cost of electricity it is also necessary to examine other efficiency criteria for investments in NPP – the internal profitability norm and the discounted payback time of investments – and their impact on the primary profitability criterion of an NPP project – the pure discounted income. The analytical interconnection of the pure discounted income, internal profitability norm of a project, and the discounted payback time of investments, which is obtained using an exponential discounting function for the expected cash flows, is shown. The requirements of the engineering and economic parameters of NPP that make NPP competitive on the world market are formulated from an analysis of the interrelation of investment efficiency criteria. The NPP investment risk evaluated by the Monte Carlo method with prescribed uncertainty of prediction of cash flows during construction and operation of NPP is presented.