C. RADIATION DOSE LIMITS The radiation dose in Figures 4, 5 and 6 is point dose at the center of the spherical aluminum shell with 4tt steradian solid angle reception. This can be considered tissue equivalent dose to the skin by dividing by 2 for 2tt steradian reception. Proper shielding of the occupational environment must be achieved in order to be consistent with the radiation protection guides and constraints. Table 9 shows the allowable radiation dose limits for manned spaceflight in Skylab, Shuttle and space station/base programs (Ref. 11) and may be used as preliminary radiation protection guides and constraints for the SPS system. 1. May be allowed for two consecutive quarters followed by 6 months of restriction from further exposure to maintain yearly limit. 2. These dose and dose-rate limits are applicable only where the possibility of oligospermia and temporary infertility are to be avoided. For most manned spaceflights, the allowable exposure accumulation to the Germinal Epithelium (3 cm) will be the subject of a risk/gain decision for the particular program, mission, and individuals concerned. Table 9. Radiation Exposure Limits and Exposure Rate Constraints for Unit Reference Risk (Ref. 11) Biological Dose Through Specified Thickness, (REM) Bone Skin Eye 2 Testes Exposure Period (5 cm) (0.1 cm) (3 mm) (3 mm) 1-year avg. daily rate 0.2 0.6 0.3 0.3 30-day maximum 25 75 37 13 Quarterly maximum^ 35 105 52 18 Yearly maximum 75 225 112 38 Career limit 400 1200 600 200
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