Measurement of neutron emission rates in the Los Alamos graphite pile

Journal Article · Sat Jun 01 04:00:00 EDT 1996 · Health Physics

OSTI ID:393961

Clement, R S; Hsu, H H; Rodriguez, J F; Olsher, R H; Casson, W H ^[1]

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1. Los Alamos National Laboratory, NM (United States)

The Los Alamos Graphite Pile is used to measure the neutron emission rate of a variety of neutron sources against a secondary standard {sup 239}Pu/Be (Q{sub s} = 8.085 E+5 n s{sup -1}) neutron source in a reproducible geometry. The Graphite Pile is a National User Facility and is available to external customers for calibrating neutron sources. The cadmium-lined Pile has dimensions of 152.6 cm (L) x 152.6 cm (W) x 254.5 cm (H). Source-to-detector distances in the Pile can range from 21 cm (for weak source strengths) to 81 cm (for strong source strengths). Observations, benchmarked by Monte Carlo calculations, were made of relative count rates for several neutron sources at various source-to-detector distances. Results show that measurement of neutron emission rates can be determined within a few percent in comparison to the secondary standard source, and are also in close agreement in comparison to MCNP calculations. In the near future we intend to replace the {sup 239}Pu/Be neutron source with a NIST-traceable ANSI-type neutron source. This primary standard neutron source will eliminate concern for the increase in the rate of neutron emissions through {sup 241}Am ({alpha},n), which adds to the {sup 239}Pu/Be neutron source`s emission rate and may lead to uncertainty in count rate measurements.

• OSTI ID: 393961
• Report Number(s): CONF-9607135--
• Journal Information: Health Physics, Journal Name: Health Physics Journal Issue: Suppl.6 Vol. 70; ISSN HLTPAO; ISSN 0017-9078
• Country of Publication: United States
• Language: English

Related Subjects

07 ISOTOPE AND RADIATION SOURCES
CALIBRATION
COUNTING RATES
GRAPHITE
NEUTRON EMISSION
NEUTRON SOURCES