Accession Number:

ADA616555

Title:

Proof of Principle for Active Detection of Fissionable Material Using Intense, Pulsed-Bremsstrahlung-Induced Photofission

Descriptive Note:

Memorandum rept. May 2010-Sep 2012

Corporate Author:

NAVAL RESEARCH LAB WASHINGTON DC PLASMA PHYSICS DIV

Personal Author(s):

• Commisso, R. J.
• Schumer, J. W.
• Allen, R. J.
• Hinshelwood, D. D.
• Jackson, S. L.
• Murphy, D. P.
• Swanekamp, S. B.
• Weber, B. V.
• Zier, J. C.
• Phlips, B. F.
• Hutcheson, A. L.
• Johnson, W. N.
• Mitchell, L. J.
• Wulf, E. A.
• Woolf, R. S.
• Apruzese, J. P.
• Cooperstein, G.
• Mosher, D.
• Hunt, A. W.
• Larsen, Z. M.

Report Date:

2014-10-07

Pagination or Media Count:

33.0

Abstract:

Photons of the appropriate energy can induce photofission in fissile material. We are investigating the applicability of this mechanism, using photons from bremsstrahlung, for long-range 100 m detection of fissile material using high-power 1 TW, pulsed technology so called intense, pulsed active detection. In this report, we describe the results of laboratory, proof-of-principle experiments, supported by computations and analyses, in which a single pulse of 8-MeV endpoint bremsstrahlung from the Naval Research Laboratory Mercury pulsed-power generator 200-kA peak current, 50-ns pulse width induces photofission in depleted uranium. Fission products are measured using He-3 proportional counters, and plastic BC408, sodium-iodide NaITl, and bismuth-germinate-oxide scintillators. Prompt neutrons, delayed neutrons, and delayed gamma-rays from the induced photofission are measured unambiguously. Delayed neutron and gamma-ray measurements are also carried out with various thicknesses of low- and high-atomic-number materials attenuating the bremsstrahlung and fission signatures. Results of simulations and analyses carried out in support of the experiments are in agreement with the measurements. In addition, we demonstrate that relatively simple variations of the diode geometry can increase the efficiency of inducing fissions three-fold over the original geometry. These geometry changes cause the electron beam to be more normally incident onto the tantalum converter and thereby increase the forward-directed bremsstrahlung intensity without changing the driving, electrical power pulse. The results of this work and future directions for this research are presented in this report.

Descriptors:

• *DETECTION
• *FISSIONABLE MATERIALS
• ATTENUATION
• BREMSSTRAHLUNG
• ELECTRON BEAMS
• FISSION
• FISSION PRODUCT ACTIVITY
• FISSION PRODUCTS
• GAMMA RAYS
• LONG RANGE(DISTANCE)
• MEASUREMENT
• NEUTRONS
• PHOTONS

Subject Categories:

• Radioactivity, Radioactive Wastes and Fission Products
• Fission Reactor Materials
• Nuclear Physics and Elementary Particle Physics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE