Active Interrogation using Photofission Technique for Nuclear Materials Control and Accountability

Technical Report · Thu Mar 31 00:00:00 EDT 2016

DOI:https://doi.org/10.2172/1303155· OSTI ID:1303155

Yang, Haori ^[1]

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1. Oregon State Univ., Corvallis, OR (United States)

Innovative systems with increased sensitivity and resolution are in great demand to detect diversion and to prevent misuse in support of nuclear materials management for the U.S. fuel cycle. Nuclear fission is the most important multiplicative process involved in non-destructive active interrogation. This process produces the most easily recognizable signature for nuclear materials. In addition to thermal or high-energy neutrons, high-energy gamma rays can also excite a nucleus and cause fission through a process known as photofission. Electron linear accelerators (linacs) are widely used as the interrogating photon sources for inspection methods involving photofission technique. After photofission reactions, prompt signals are much stronger than the delayed signals, but it is difficult to quantify them in practical measurements. Delayed signals are easily distinguishable from the interrogating radiation. Linac-based, advanced inspection techniques utilizing the delayed signals after photofission have been extensively studied for homeland security applications. Previous research also showed that a unique delayed gamma ray energy spectrum exists for each fissionable isotope. In this work, high-energy delayed γ-rays were demonstrated to be signatures for detection, identification, and quantification of special nuclear materials. Such γ-rays were measured in between linac pulses using independent data acquisition systems. A list-mode system was developed to measure low-energy delayed γ-rays after irradiation. Photofission product yields of ²³⁸U and ²³⁹Pu were determined based on the measured delayed γ-ray spectra. The differential yields of delayed γ-rays were also proven to be able to discriminate nuclear from non-nuclear materials. The measurement outcomes were compared with Monte Carlo simulation results. It was demonstrated that the current available codes have capabilities and limitations in the simulation of photofission process. A two-fold approach was used to address the high-rate challenge in used nuclear fuel assay based on photofission technique. First, a standard HPGe preamplifier was modified to improve its capabilities in high-rate pulsed photofission environment. Second, advanced pulse processing algorithms were shown to greatly improve throughput rate without large sacrifice in energy resolution at ultra-high input count rate. Two customized gamma spectroscopy systems were also developed in real-time on FPGAs. They were shown to have promising performance matching available commercial units.

• Research Organization: Battelle Energy Alliance, LLC, Idaho Falls, ID (United States)
• Sponsoring Organization: USDOE Office of Nuclear Energy (NE)
• DOE Contract Number: AC07-05ID14517
• OSTI ID: 1303155
• Report Number(s): 11-3035; 11-3035; TRN: US1601788
• Country of Publication: United States
• Language: English

Related Subjects

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL PROTECTION
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
PHOTOFISSION
NUCLEAR MATERIALS MANAGEMENT
DELAYED GAMMA RADIATION
FISSILE MATERIALS
LINEAR ACCELERATORS
DETECTION
GAMMA SPECTRA
PLUTONIUM 239 TARGET
URANIUM 238 TARGET
FISSION PRODUCTS
YIELDS
MONTE CARLO METHOD
COMPUTERIZED SIMULATION
PREAMPLIFIERS
ALGORITHMS
DATA PROCESSING
GAMMA SPECTROSCOPY
SIGNALS
INSPECTION
NUCLEAR FUELS
PULSES
NUCLEAR REACTION ANALYSIS