• Nuclear Engineering and Technology
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• v.3 no.2
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• pp.65-75
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• 1971

The gamma-ray shielding effects of magnetite concretes have been measured using a broad beam Co-60 gamma-ray source. Mathematical formulae for a trans-mission ratio-to-shield thickness relation were derived from the attenuation curve obtained experimentally and are I (x) = I (ο) exp(-$\mu$X) exp(1.03$\times$10$^{-1}$ X-3.38$\times$10$^{-3}$ X$^2$＋5.29$\times$10$^{-5}$ X$^3$) when X< 20 cm, I (x) =I (ο) exp(-$\mu$X) exp(4.66$\times$10$^{-2}$ X＋2.12$\times$10$^{-1}$ ) when X＞20 cm. Here I (x) is radiation intensity after passing through a thickness X of absorber, I(o) is the initial radiation intensity, $\mu$ is the linear attenuation coefficient of magnetite concrete and is given by (0.0532$\rho$＋ 0.0083)$^{4)}$ $cm^{-1}$ / in accordance with an earlier study, and X is the thickness of absorber. In addition, a model shield which is a rectangular magnetite concrete box with walls of 8cm thickness walls and internal demensions of 40$\times$40$\times$40 cm was constructed and its shielding effect has been measured. The emergent radiation flux appears to be greater with this configuration than with a slab shield of equal thickness.

• Nuclear Engineering and Technology
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• v.8 no.3
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• pp.145-150
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• 1976

Alkali-treated red algae, Gracilaria sp. was irradiated with various doses of cobalt-60 gamma-rays and the yeild and properties of agar extracted from the seaweed were examined and compared with the quality of commercial agar powder after irradiation. Extraction yield of agar from irradiated seaweed was proportionally increased as the radiation dose was raised up to 2 Mrad whereas it tended to decrease slightly thereafter. Gelation ability, gelation point, gel hardness and specific viscosity of the agar were increased up to 1 Mrad and decreased at higher dose levels while its melting point, total nitrogen, crude ash and total sulfur decreased up to 1 Mrad level and remained unchanged thereafter. Irradiation of commercial agar powder caused remarkable decreases in the gelation ability, specific viscosity and gel hardness and slight decreases in the gelation point and melting point. The pattern of alterations in the properties of agar samples differed whether the polysaccharide was irradiated in free state or bound state in seaweed.