Report on NRL measurements as a participant in the INDI. Final report

Technical Report · Thu May 01 04:00:00 EDT 1975

OSTI ID:7365168

Attix, F H; Theus, R B; Gorbics, S G; Rogers, C C

NRL was invited to participate in the International Neutron Dosimetry Intercomparison (INDI) which took place during 1973 at the Raiological Research Accelerator Facility of Brookhaven National Laboratory, under the sponsorship of the International Commission on Radiation Units and Measurements. The source was a D-T generator of 15.5-MeV neutrons. Measurements were made only along the extended axis of the deutron beam; at 30 cm in free space, and at depths of 5, 10, and 20 cm in a 30 cm cubic water phantom positioned with its input face 20 cm from the neutron source. A 1-cc tissue-equivalent (TE) ion chamber was used with TE gas or air flowing through it to measure the total n+gamma dose in tissue, with appropriate corrections. Thermoluminescent dosimeters were employed to measure the gamma-ray dose component, assuming that the n/gamma sensitivity ratio measured in the NRL neutron beam (approx. 15 MeV average energy) was appropriate to the free-space measurement for the INDI. The gamma-ray dose component at 30 cm from the target is negligible in free space, probably not exceeding a few tenths of a percent of the total dose there. Within the phantom it is necessary to make a correction to the (n/gamma) sensitivities of the TLD's to account for the degradation of neutron energy with depth. The neutron spectrum at 5 cm, 10 cm, and 20 cm depth has been estimated by Herling through Monte Carlo calculations. (GRA)

• Research Organization: Naval Research Lab., Washington, D.C. (USA)
• OSTI ID: 7365168
• Report Number(s): AD-A-012339; NRL-MR-3051
• Country of Publication: United States
• Language: English

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