Photo-fission Literature
Photonuclear-based, nuclear material detection system for cargo containers
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5 kg HEU, 1 m from cargo container wall, @15 MeV 2.12E-06 induced fissions
per gamma… from our calculation we are getting approximately 10-5
fissions per particle (about 2000 fissions) but we are using uranium
238 with a lower cross section
With 5 kg of HEU, the approximate surface area would be about 100 cm2
Photofission-based, Nuclear Material Detection: Technology Demonstration
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4.8 kg HEU and 4.4 kg DU, 6 MeV 3 micro-Amp of IEEL Varitron, 120
interrogation times, He-3 detectors, focus on detecting delayed neutrons,
LANL Detector 122 cm x 244 cm x 15 cm (height, length, thickness), 150 cm
from centerline, INEEL detector: 2.54 cm diameter, 76.3 cm long He-3 tube,
neutron efficiency of 3E-4 counts per Cf source fission neutron @ 100 cm for
INEEL detector, 22 INEEL detectors for Eagle configuration, INEEL ~1200
cm2, LANL ~30000 cm2
o Used 4 INEEL detectors at 100 cm from 4.4 kg DU target at 105 cm
forward of the photon source and received delayed neutron counts of
1.3, 1.6, 1.7, and 1.5 @ 6.1 MeV
Photonuclear-based Detection of Nuclear Smuggling in Cargo Containers
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50 Hz, 3 micro-second, 6 MeV
4.4 kg DU at 1 meter, 4 He-tubes 76 cm long 2.54 cm diameter, Another He-3
detector 2.4 meters long/1.5 m tall/0.15 meters wide about 1 meter away,
o For the 4 detectors DU only 1.36, 1.22, 1.06, 1.00 cps for 6 MeV for
delayed neutrons, 6.2, 5.8, 4.6, and 4.3 prompt neutrons
Assume 300 cm2 for one He-3 tube with 0.12% efficiency and approximately
5 neutrons per second are registered by the detector making the total
neutrons incident on the detectors approximately 4000 neutrons per
second
Detection of shielded nuclear material in a cargo container
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3 to 4 micro-Amos average beam current @ 125 Hz
10 MeV photon interrogation of a 4.8 kg DU sample, 14 cm square DU sample,
120 seconds, photon source is 250 cm away, detector is 122 cm away, at
detector #3… 9.97E-13, at detector #16… 5.62E-13 both per e, operates at 3
to 4 micro-amps which would give about 0.17 neutrons per second @ 10
MeV photon energy for detected
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Assumed efficiency for He-3 tube is 0.12% making total neutrons incident on
the detector about 140 neutrons per second as compared to 0.5 neutrons
per second.
Detecting Nuclear Warheads
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A much smaller number of fissions are generated per source photon than per
source neutron for two reasons: a much larger fraction of the photons are
absorbed before they can reach the fissile material, and, of those reaching the
fissile material, a smaller fraction induce fissions.
The use of high-energy photons for Photofission (>14 MeV) leads to a large
number of (gamma, n) reactions in other material.
A detection distance of ten meters would require an isotropic source of
nearly 1010 5.5 MeV gamma rays per second