skip to main content

SciTech ConnectSciTech Connect

Title: Active Interrogation using Photofission Technique for Nuclear Materials Control and Accountability

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 tomore » 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.« less
Authors:
 [1]
  1. Oregon State Univ., Corvallis, OR (United States)
Publication Date:
OSTI Identifier:
1303155
Report Number(s):
11-3035
11-3035; TRN: US1601788
DOE Contract Number:
AC07-05ID14517
Resource Type:
Technical Report
Research Org:
Battelle Energy Alliance, LLC, Idaho Falls, ID (United States)
Sponsoring Org:
USDOE Office of Nuclear Energy (NE)
Country of Publication:
United States
Language:
English
Subject:
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