PC/FRAM: a code for the nondestructive measurement of the isotopic composition of actinides for safeguards applications

The Nuclear Safeguards Program at the Los Alamos National Laboratory has developed and fielded techniques for the gamma-ray spectrometry measurement of the isotopic composition of plutonium and other actinides for over 20 years, ever since Parker and Reilly first proposed a practical method for the measurement of the arbitrary sample. Their procedures, incorporating internal (to the measured gamma-ray spectrum) or {open_quotes}intrinsic{close_quotes} self-determination of the relative efficiency function of the sample-detector measurement system, are widely applied today. The PC/FRAM code is the most recent and most highly-developed Los Alamos code developed specifically for the nuclear safeguards applications of this technique. We will describe the measurement principles that allow accurate measurements to be taken on samples of arbitrary size, shape, and measurement geometry- and of arbitrary physical and chemical composition-through the use of known nuclear decay data (half-lives and branching intensities). Subsequently, we will describe the analysis methodology, which is driven by an easily edited parameter file that frees the user from dependence on a dedicated programmer for analyses of special cases. This methodology relies on internal gamma-ray peaks from the spectrum under analysis to self-calibrate the unknown spectrum for energy and peak shape (energy dependence of full width at half maximum (FWHM) and tailing parameters). The program uses these parameters to calculate response functions that are fit to the analysis peaks requested in the parameter file. The structure of the code and its Windows 3.1 user interface allows use with equal ease by the experienced spectroscopist or operator-level personnel in a working facility.

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PC/FRAM: A code for the nondestructive measurement of the isotopic composition of actinides for safeguards applications

A nondestructive method based on low-energy, high-resolution photon spectrometry is presented which allows accurate determination of (239)Pu, (240)Pu, and (241)Am (as a daughter of (241)Pu) activities in radioactive particles containing relatively high levels of plutonium isotopes. The proposed method requires only one measurement for the establishment of an absolute efficiency curve. Since the density and composition of the radioactive particles of interest may vary, a self-absorption correction is required for the accurate determination of isotopic activities and ratios. This correction is carried out for each individual particle using the convenient gamma-ray emissions of (241)Am.

(239)Pu, (240)Pu, and (241)Am determination in hot particles by low level gamma-spectrometry.

Combating the threat of nuclear smuggling through shipping ports and border crossings has been recognized as a national priority in defending the US against nuclear terrorism. In light of the SAFE Port act of 2006, the Domestic Nuclear Detection Office (DNDO) has been charged with the responsibility of providing the Customs and Border Protection Agency (CBP) with the capability to conduct 100% radiological screening of all containers entering the country. In an attempt to meet this mandate, the DNDO has conducted a typical government acquisition procedure to develop and acquire radiation portal monitors (RPMs) capable of passive gamma-ray spectroscopy that would allow 100% radiological screening without detrimental affects on the stream of commerce through the terminals. However, the Cost-Benefit Analysis (CBA) supporting the DNDO decision-making process has been criticised and has delayed the program significantly. We propose an Analytic-Deliberative Process (ADP) as an alternative to CBA for this application. We conduct a case study with four DNDO stakeholders using the ADP proposed by the National Research Council in the context of environmental remediation and adapted by the MIT group and compare the results to those derived from DNDO's CBA. The process involves value modeling using an objectives hierarchy and the analytic hierarchy process. Value functions are derived and expected outcomes for the decision options are elicited from the stakeholders. The process results in a preference ranking of the decision options in order of value to each stakeholder. The analytical results are then used to structure a deliberation in which the four stakeholders use both the analytical results and any pertinent information outside the analysis to form a consensus. The final decision of both the CBA and ADP models show good agreement and demonstrate the validity of both methods. However, the ADP format is better at explicitly capturing and quantifying subjective influences affecting the final decision. This facilitates discussion and leads to faster consensus building. Thesis Supervisor: George E. Apostolakis Title: Professor of Nuclear Engineering Professor of Engineering Systems (This page intentionally left blank)

An analytic-deliberative process for the selection and deployment of radiation detection systems for shipping ports and border crossings

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Alternative Method for Determining Plutonium-240 Content

We discuss the general approach, computerized data analysis methods, and results of measurements to determine the isotopic composition of plutonium by gamma-ray spectroscopy. The simple techniques are designed to be applicable to samples of arbitrary size, geometry, chemical and isotopic composition that have attained /sup 241/Pu-/sup 237/U equilibrium. The combination of the gamma spectroscopic measurement of isotopic composition coupled with calorimetric measurement of total sample power is shown to give a totally nondestructive determination of sample Pu mass with a precision of 0.6% for 1000-g samples of PuO/sub 2/ with 12% /sup 240/Pu content. The precision of isotopic measurements depends upon many factors including sample size, sample geometry, and isotopic content. Typical ranges are found to be /sup 238/Pu, < 1 to 10%; /sup 239/Pu, 0.1 to 0.5%; /sup 240/Pu, 2 to 5%; /sup 241/Pu, 0.3 to 0.7%; /sup 242/Pu (determined by isotopic correlation); and /sup 241/Am, 0.2 to 10%.

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Plutonium isotopic composition by gamma-ray spectroscopy

We discuss the general approach, computerized data analysis methods, and results of measurements used to determine the isotopic composition of plutonium by gamma-ray spectroscopy. The simple techniques are designed to be applicable to samples of arbitrary size, geometry, age, chemical, and isotopic composition. The combination of the gamma spectroscopic measurement of isotopic composition coupled with calorimetric measurement of total sample power is shown to give a totally nondestructive determination of sample plutonium mass with a precision of 0.6% for 1000-g samples of PuO/sub 2/ with 12% /sup 240/Pu content. The precision of isotopic measurements depends upon many factors, including sample size, sample geometry, and isotopic content. Typical ranges are found to be /sup 238/Pu, 1 to 10%; /sup 239/Pu, 0.1 to 0.5%; /sup 240/Pu, 2 to 5%; /sup 241/Pu, 0.3 to 0.7%; /sup 242/Pu (determined by isotopic correlation); and /sup 241/Am, 0.2 to 10%.

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S.T. Hsue

Papers

Plutonium isotopic composition by gamma-ray spectroscopy

Determination of plutonium isotopic composition by gamma-ray spectroscopy