Early results utilizing high-energy fission product (gamma) rays to detect fissionable material in cargo

Journal Article · Thu Sep 30 00:00:00 EDT 2004 · Nuclear Instruments & Methods B, vol. 241, no. 1-4, August 30, 2005, pp. 777-781

OSTI ID:991521

Slaughter, D R; Accatino, M R; Bernstein, A; Church, J A; Descalle, M A; Gosnell, T B; Hall, J M; Loshak, A; Manatt, D R; Mauger, G J; McDowell, M; Moore, T M; Norman, E B; Pohl, B A; Pruet, J A; Petersen, D C; Walling, R S; Weirup, D L; Prussin, S G

A concept for detecting the presence of special nuclear material ({sup 235}U or {sup 239}Pu) concealed in intermodal cargo containers is described. It is based on interrogation with a pulsed beam of 7 MeV neutrons that produce fission events and their {beta}-delayed neutron emission or {beta}-delayed high-energy {gamma}-radiation between beam pulses provide the detection signature. Fission product {beta}-delayed {gamma}-rays above 3 MeV are nearly ten times more abundant than {beta}-delayed neutrons and are distinct from natural radioactivity and from nearly all of the induced activity in a normal cargo. Detector backgrounds and potential interferences with the fission signature radiation have been identified and quantified. An important goal in the US is the detection of nuclear weapons or special nuclear material (SNM) concealed in intermodal cargo containers. This must be done with high detection probability, low false alarm rates, and without impeding commerce, i.e. about one minute for an inspection. The concept for inspection has been described before and its components are now being evaluated. While normal radiations emitted from plutonium may allow its detection, the majority of {sup 235}U {gamma} ray emission is at 186 keV, is readily attenuated by cargo, and thus not a reliable detection signature for passive detection. Delayed neutron detection following a neutron or photon beam pulse has been used successfully to detect lightly or unshielded SNM targets. While delayed neutrons can be easily distinguished from beam neutrons they have relatively low yield in fission, approximately 0.008 per fission in {sup 239}Pu and 0.017 per fission in {sup 235}U, and are rapidly attenuated in hydrogenous materials making that technique unreliable when challenged by thick hydrogenous cargo overburden. They propose detection of {beta}-delayed high-energy {gamma} radiation as a more robust signature characteristic of SNM.

• Research Organization: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 991521
• Report Number(s): UCRL-JRNL-207073; TRN: US1007513
• Journal Information: Nuclear Instruments & Methods B, vol. 241, no. 1-4, August 30, 2005, pp. 777-781, Vol. 241, Issue 1-4
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
98 NUCLEAR DISARMAMENT
SAFEGUARDS AND PHYSICAL PROTECTION
CARGO
CONTAINERS
DELAYED NEUTRONS
DETECTION
FISSION
FISSION PRODUCTS
FISSIONABLE MATERIALS
NATURAL RADIOACTIVITY
NEUTRON EMISSION
NEUTRONS
NUCLEAR WEAPONS
OVERBURDEN
PHOTON BEAMS
PLUTONIUM
PROBABILITY
RADIATIONS
TARGETS
TRADE