Vladimir Novikov

Structure-Phase Changes and Corrosion Behavior of E110 and E635 Claddings of Fuels in Water Cooled Reactors

Data are discussed pertaining to influence of in-pile irradiation on microstructure, tensile and corrosion properties of E110 and E635 cladding samples taken along fuel rods that have operated for ~5 and 3 years in RBMK and VVER-1000 reactors, respectively. In the initial condition the E110 cladding structure was a recrystallized one while that of E635 was partially re-crystallized. Irradiation has lead to the almost full recrystallization of the E635 alloy cladding. The original structure basically comprising a-type dislocation transforms into the structure that features the high density of the a-type dislocation loops. No dislocations of the c-type were identified in the cladding samples of both the alloys. Changes in the composition of the β-Nb particles in the E110 alloy claddings and changes in Laves phase particle composition in the E635 claddings were revealed. The results on the in-pile corrosion of the E110 and E635 claddings are reviewed in comparison to the results of the autoclave tests. The interrelation is discussed between the irradiation hardening and irradiation induced corrosion of E110 and E635 claddings as attended by the evolution of the structure-phase condition of those alloys.

Reactivity accident of nuclear submarine near Vladivostok

After the collapse of the Soviet Union and consequently the termination of the Cold War and the disarmament agreements, many nuclear warheads are in a queue for dismantling. As a result, substantial number of nuclear submarines equipped with ballistic missiles will be also withdrawn from service. However, Russian nuclear submarines have suffered from reactivity accidents five times. In the paper, a reactivity accident on a nuclear submarine that happened at Chazhma Bay located between Vladivostok and Nakhodka on August 10, 1985, has been described. In addition, the characteristics of submarine nuclear reactors, procedures of refueling, and the possibility of a similar accident are given. Further, the radiological risk to Japan and neighboring countries has been assessed by using an atmospheric pollutant transport code, WSPEEDI, developed by Japan Atomic Energy Research Institute. The radiological risk has been evaluated for the Chazhma Bay accident and for a hypothetical reactivity accident of a retired submarine during defueling, assuming winter meteorological conditions. The analyses have shown that the radioactive material might be transported in the atmosphere to Japan in one to several days and might contaminate wide areas of Japan. Under the assumptions taken in the paper, however, the radiological dose to population in the area might be not significant.

Temperature dependences of the delayed hydride cracking rate of fuel claddings made of zirconium alloys of various compositions

The temperature dependences of the delayed hydride cracking (DHC) rate of Zr-1Nb and Zr-0.8Nb-0.8Sn-0.3Fe alloy claddings are studied in the range 127–300°C in comparison with the data obtained for Zr-2.5Nb and Zircaloy-4 alloys earlier. The samples are in the state of cold deformation and stress relief at 400°C for 24 h and in the state of preliminary hydrogen saturation to a hydrogen concentration of 0.02 wt %. As the strength of a zirconium alloy decreases and its ductility increases, the DHC rate and its high-temperature limit for a linear Arrhenius equation decreases, and the fractographic patterns of the fracture surfaces are different.