A Conceptual design study of space nuclear power plant SECTRA (II); Investigation of shielding structure

Nomura, Norio; Haga, Kazuo;

PNC TN9410 91-125, 75 Pages, 1991/04

PNC-TN9410-91-125.pdf:1.87MB

Within a framework of transportable reactor study, a conceptual design of power source to lunar base or space station is being performed. In the lunar base power plant SPECTRA-L, dose equivalent at the area around the reactor can be reduced till the natural back ground level by the shield of regolish. But, it is not easy to reduce the dose equivalent to an acceptable level the limit of dose equivalent from the reactor. Because shields abobe the reactor are only thin regolish whose thickness are 2m, and plant equipments such as boiler, condenser, alternator, and turbine. In case of SPECTRA for the space station, shield must be furnished from the beginning. In this report, shielding structure of SPECTRA is analyzed seeking for an optimum one. The analytical condition are as follows. (1)Thickness of shield is less than 1 m. (2)Weight is as light as possible. The finally obtained shielding structure is a layer by Beryllium, tungsten, lithium-hydrogen, and SUS304. These total thickness is 90cm. Using this shield, the dose equivalent rate at 25m apart point from the reactor, where life module will be located, is estimated to be 14.4Sv/h. This value is more than a proposed limit of dose equivalent from the reactor (40mSv/y : 4.6 Sv/h). But it is expected that the actual dose equivalent is less than the limit value owing to the plant equipment in the direction and the life module shield of cosmic ray.