Neutron and gamma ray attenuation of asphalt; Comparison with paraffin and water
- KAAU, Jeddah (Saudi Arabia)
Asphalt is a low cost, readily available, easy-to-cast material which is rich in hydrogen and carbon, elements most effective for fast-neutron shielding. Unlike paraffin, the material can easily be mixed with boron containing compounds, an, element of high absorption cross-section for slow neutrons. The {sup 241}Am-Be neutron and gamma attenuation characteristic of asphalt were studied. The source is having wide applications in industry and geophysics field work. Comparisons were made with paraffin and water. The source activity was 1.11 x 1,011 Bq (3 Ci) with a neutron emission rate of 6.6 x 106 n s{sup -1} and a tolerance of +10%. The neutron dose-equivalent rate at 1 m was 66 mSv h{sup -1}, while the associated gamma ray exposure was {approximately}1.9 mC kg{sup -1} h{sup -1} of the bare source. A neutron remmeter was used for the neutron dose-equivalent rate measurements, which produces an energy response that approximates human body dose equivalent over a wide range of neutron energy. An air filled ionization chamber was used for the exposure rate measurements. The slow neutrons were measured by a BF{sub 3} gas filled detector. The shielding materials were confined in an aluminum cylinder of 1 mm wall thickness where the source was kept in the middle. The neutron dose rate, the gamma ray exposure rate, and the slow neutron count rate were measured at different shield radii and at different distances from its outer surface. The neutron doses of asphalt at the surface of cylindrical shields of 8, 12, 16, 20, and 24 cm radii in mSv h{sup -1} were 0.85, 0.4, 0.25, 0.13, and 0.06, respectively, while the gamma ray exposure mC kg{sup -1} h{sup -1} were 7, 4.4 2.5, 1.3, and 0.88, respectively. The neutron dose rate attenuation of asphalt was very close to that of water, but slightly lower than that of paraffin, while the gamma ray attenuation was close to that of water but higher than that of paraffin.
- OSTI ID:
- 394007
- Report Number(s):
- CONF-9607135-; ISSN 0017-9078; TRN: 96:028688
- Journal Information:
- Health Physics, Vol. 70, Issue Suppl.6; Conference: 41. Annual Meeting of the Health Physics Society, Seattle, WA (United States), 21-25 Jul 1996; Other Information: PBD: Jun 1996
- Country of Publication:
- United States
- Language:
- English
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