Activation of electrical machinery. Supplement 1. [Preliminary evaluation; not applicable to ground tests]
Description: The following analysis of the induced radioactivity in SNAP-50/SPUR electrical machinery having a high cobalt content is submitted. Induced radioactivity in the flight vehicle will contribute negligibly to allowable radiation levels. This is especially so due to the low neutron to gamma ratio of assumed radiation damage tolerances to semiconductors. A calculation to estimate the order of magnitude of induced radioactivity in cobalt is attached. The calculation is based on a best guess of the neutron spectrum directly behind a lithium hydride shield. The resulting low cobalt activity and associated dose rate of about 1 mr/hr at 10 ft from a generator or a motor is insignificant. Although the evaluation indicates insignificant levels of induced radioactivity, this conclusion is not applicable to a ground test. Neutron moderation and scattering from a containment vessel and biological shield would greatly perturb the neutron environment behind the flight shield. Posttest handling of all components within the vacuum test chamber will undoubtedly be a problem. Notwithstanding the importance of limiting induced radioactivity, other considerations such as economy, cooling and vacuum requirements will largely dictate the final facility design. In summary, an activation analysis involves the overall facility design and will not be readily resolved. For a 10,000 hr. test the Co/sup 60/ activity may range from 100 curies per lb of cobalt where no shielding is provided to 10/sup -3/ curies per lb of cobalt where the equivalent of a flight shield is provided.
Date: November 15, 1963
Creator: Smolen, J.R.
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