William H. Geist

An approach to multiplicity counting for a versatile new sensor for plutonium assay with a very short die-away time, and independent measurements of neutrons and gamma rays

Abstract A unique detector design incorporating a 6Li-based capture medium, ZnS scintillator, and wavelength shifting optical fibers is the basis of a new neutron coincidence counter for measurements of plutonium in highly impure residues. The sensor elements have a high efficiency for detecting neutrons and exhibit excellent gamma-ray discrimination based on pulse-shape analysis. The short die-away time of the counter that is based on these detector elements allows coincidence-gate settings shorter than 10xa0μs. This qualifies the technology for measurements of materials with high yields of uncorrelated neutrons from 241Am(α,n) reactions. The characteristics of the new neutron counter will be illustrated with test data from measurements of plutonium, 252Cf, and gamma-ray sources. The integrated electronics design of the new detector also permits the simultaneous but independent measurement of both neutrons and gamma rays. Recent test results that illustrate some unique applications of the sensors versatility will also be presented.

Evaluation of a fast neutron coincidence counter for the measurements of uranium samples

Abstract A fast neutron coincidence counter using BC454/BGO phoswich detectors has been evaluated for the purpose of rapid verification measurements of uranium items. This counter uses custom electronics to identify and count coincidence neutrons in the presence of background radiation. Measurements of uranium standards were performed to evaluate the counter. This counter is successful in measuring uranium items but has a low efficiency that results in minimal improvement over current technology. An optimized counter can be built with better performance capabilities, but it is recommended that newer technologies be used instead.

Boron-lined parallel-plate Collar

This report presents boron-lined parallel plate technology features, experimental benchmarking of initial MCNP model, and parallel-plate UNCL collar optimization.

Improving Neutron Measurement Capabilities; Expanding the Limits of Correlated Neutron Counting

A number of technical and practical limitations exist within the neutron correlated counting techniques used in safeguards, especially within the algorithms that are used to process and analyze the detected neutron signals. A multi-laboratory effort is underway to develop new and improved analysis and data processing algorithms based on fundamental physics principles to extract additional or more accurate information about nuclear material bearing items.

LANL Efforts on Neutron Coincidence Modeling of INL Pulsed Neutron Data

Overview of this presentation is: (1) pulsed histogram analysis, (2) creation of SPNS, (3) use of SPNS for modeling pulsed neutron data, (4) creation of MUDI, (5) calculated accidentals correction using GUAM + MUDI, (6) background subtraction analysis, and (7) current/figure work with MCNP.

Analytical Techniques in Nuclear Safeguards

In this chapter, we present an overview of the measurement and analysis techniques used to quantify the mass of special nuclear material in containers that are typically sealed. Other item characteristics, such as enrichment for uranium or isotopic composition for plutonium, may also be measured. These measurements are performed in support of safeguards objectives. Nuclear safeguards is the system of policies and technical measures developed to ensure that fissionable materials are being used for their intended purposes and are controlled through the implementation of technologies, procedures, and policies. Fissionable material of safeguards concern is often referred to as Special Nuclear Material (SNM). The most commonly performed measurement techniques fall into one of three categories: photon measurements, which include x-ray, gamma-ray, and Cerenkov radiation; neutron measurements, which include the use of total neutron rates or careful analysis of the time correlation between neutron detection events (neutron coincidence analysis or neutron multiplicity analysis); and heat flow calorimetry, the measurement of the decay heat produced by nuclear materials, primarily through alpha particle decay. In almost every case, the results obtained from more than one of these measurements must be combined to obtain the mass of special nuclear material. The most common analytical techniques are discussed in terms of theory of operation, limitations, accuracy/precision, and operational considerations. This chapter is not an exhaustive discussion of the measurement techniques applied to special nuclear material in safeguards or for other reasons, but it should serve as an excellent starting point for studying the topic, and further information for more detailed study is available in the references or in the publications of the Institute for Nuclear Material Management or the International Atomic Energy Agency.