Radiation shielding in the formation of the structural aspect of a spaceship with a nuclear power system

Abstract

A method for obtaining a prescribed radiation environment and the effect of this environment on the general design of a spaceship with a nuclear power system and the structural implementation of individual units are presented. The algorithm developed is of high priority because of the higher power and longer service life of the newly developed nuclear power systems. Their values under the existing restrictions on the mass and the admissible flux of ionizing radiation make it problematic to meet the necessary requirements by using conventional approaches, where shadow radiation shielding served as the main factor. The design algorithm examined is generally recommended and in each specific case it can be accompanied by an anlysis of the factors present at the design stage.A special feature of the formation of the radiation environment in a spaceship with a nuclear power system (NPS) is the absence of a surrounding medium which scatters ionizing radiation. On the one hand, this dictates the stringent rules for the design, and on the other hand it makes it possible to substantially decrease, by appropriate structural-design solutions, the mass/size characteristics of the spaceship. This result follows from recent investigations which included computationaldesign works studying the influence of various design solutions on the formation of the radiation environment onboard a spaceship. The importance of these studies was due to the substantial increase in the power of the nuclear reactor as compared with the first-generation space NPS Buk [1] and Topaz [2] and the increase of service life to 10 or more years. At the same time, modern spaceships contain various large objects (refrigerators-radiators, antennas, and others) and are equipped with radioelectronic apparatus which is highly sensitive to ionizing radiation. In this connection, the radiation shielding for second-generation NPS must give an attenuation factor 10-100 times higher than the value for the first-generation NPS.One of the main results of the work is the conclusion that the existing mass limitations make it impossible to meet the requirements for admissable fluxes of ionizing radiation by equipping the NPS with conventional, in the standard meaning of this word, radiation shielding. All means available to the developer must be used. This includes equipping the NPS with shadow radiation shielding, the overall design of the spaceship, the design of the bay containing radiation-sensitive apparatus, the arrangement of the apparatus in the bay, the use of appropriate materials in individual components of the structure, and other means. All this can, to one extent or another, allow achieving the goal stated and therefore these are means for radiation shielding. Their choice, optimization, and subsequent use will make it possible ultimately to achieve the required mass/size characteristics.