skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: FY2011 Annual Report for the Actinide Isomer Detection Project

Abstract

This project seeks to identify a new signature for actinide element detection in active interrogation. This technique works by exciting and identifying long-lived nuclear excited states (isomers) in the actinide isotopes and/or primary fission products. Observation of isomers in the fission products will provide a signature for fissile material. For the actinide isomers, the decay time and energy of the isomeric state is unique to a particular isotope, providing an unambiguous signature for SNM. This project entails isomer identification and characterization and neutron population studies. This document summarizes activities from its third year - completion of the isomer identification characterization experiments and initialization of the neutron population experiments. The population and decay of the isomeric state in 235U remain elusive, although a number of candidate gamma rays have been identified. In the course of the experiments, a number of fission fragment isomers were populated and measured [Ressler 2010]. The decays from these isomers may also provide a suitable signature for the presence of fissile material. Several measurements were conducted throughout this project. This report focuses on the results of an experiment conducted collaboratively by PNNL, LLNL and LBNL in December 2010 at LBNL. The measurement involved measuring the gamma-rays emittedmore » from an HEU target when bombarded with 11 MeV neutrons. This report discussed the analysis and resulting conclusions from those measurements. There was one strong candidate, at 1204 keV, of an isomeric signature of 235U. The half-life of the state is estimated to be 9.3 {mu}s. The measured time dependence fits the decay time structure very well. Other possible explanations for the 1204-keV state were investigated, but they could not explain the gamma ray. Unfortunately, the relatively limited statistics of the measurement limit, and the lack of understanding of some of the systematic of the experiment, limit the authors to labeling the 1204-keV gamma ray as a very strong candidate for isomeric transition in 235U. Regardless of the physics origins, the time structure of the 1204-keV gamma ray can be used as at a minimum as an indication of fissile material, if the 1204-keV gamma ray is attributed to a fission product, or it may be a unique signature for 235U, if it is a signature of an isomeric state in 235U.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1029875
Report Number(s):
PNNL-20796
NN2001000; TRN: US1200050
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; ACTINIDE NUCLEI; ACTINIDES; DECAY; DETECTION; EXCITED STATES; FISSILE MATERIALS; FISSION FRAGMENTS; FISSION PRODUCTS; HALF-LIFE; ISOMERIC TRANSITIONS; ISOMERS; LAWRENCE LIVERMORE NATIONAL LABORATORY; NEUTRONS; PHYSICS; STATISTICS; TARGETS; TIME DEPENDENCE; Isomer; U-235; Candidate; Active Interrogation

Citation Formats

Warren, Glen A., Francy, Christopher J., Ressler, Jennifer J., Erikson, Luke E., Tatishvili, Gocha, and Hatarik, R. FY2011 Annual Report for the Actinide Isomer Detection Project. United States: N. p., 2011. Web. doi:10.2172/1029875.
Warren, Glen A., Francy, Christopher J., Ressler, Jennifer J., Erikson, Luke E., Tatishvili, Gocha, & Hatarik, R. FY2011 Annual Report for the Actinide Isomer Detection Project. United States. doi:10.2172/1029875.
Warren, Glen A., Francy, Christopher J., Ressler, Jennifer J., Erikson, Luke E., Tatishvili, Gocha, and Hatarik, R. Sat . "FY2011 Annual Report for the Actinide Isomer Detection Project". United States. doi:10.2172/1029875. https://www.osti.gov/servlets/purl/1029875.
@article{osti_1029875,
title = {FY2011 Annual Report for the Actinide Isomer Detection Project},
author = {Warren, Glen A. and Francy, Christopher J. and Ressler, Jennifer J. and Erikson, Luke E. and Tatishvili, Gocha and Hatarik, R.},
abstractNote = {This project seeks to identify a new signature for actinide element detection in active interrogation. This technique works by exciting and identifying long-lived nuclear excited states (isomers) in the actinide isotopes and/or primary fission products. Observation of isomers in the fission products will provide a signature for fissile material. For the actinide isomers, the decay time and energy of the isomeric state is unique to a particular isotope, providing an unambiguous signature for SNM. This project entails isomer identification and characterization and neutron population studies. This document summarizes activities from its third year - completion of the isomer identification characterization experiments and initialization of the neutron population experiments. The population and decay of the isomeric state in 235U remain elusive, although a number of candidate gamma rays have been identified. In the course of the experiments, a number of fission fragment isomers were populated and measured [Ressler 2010]. The decays from these isomers may also provide a suitable signature for the presence of fissile material. Several measurements were conducted throughout this project. This report focuses on the results of an experiment conducted collaboratively by PNNL, LLNL and LBNL in December 2010 at LBNL. The measurement involved measuring the gamma-rays emitted from an HEU target when bombarded with 11 MeV neutrons. This report discussed the analysis and resulting conclusions from those measurements. There was one strong candidate, at 1204 keV, of an isomeric signature of 235U. The half-life of the state is estimated to be 9.3 {mu}s. The measured time dependence fits the decay time structure very well. Other possible explanations for the 1204-keV state were investigated, but they could not explain the gamma ray. Unfortunately, the relatively limited statistics of the measurement limit, and the lack of understanding of some of the systematic of the experiment, limit the authors to labeling the 1204-keV gamma ray as a very strong candidate for isomeric transition in 235U. Regardless of the physics origins, the time structure of the 1204-keV gamma ray can be used as at a minimum as an indication of fissile material, if the 1204-keV gamma ray is attributed to a fission product, or it may be a unique signature for 235U, if it is a signature of an isomeric state in 235U.},
doi = {10.2172/1029875},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sat Oct 01 00:00:00 EDT 2011},
month = {Sat Oct 01 00:00:00 EDT 2011}
}

Technical Report:

Save / Share: