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Menlove, Howard O.

Publications and source records attributed to Menlove, Howard O..

15 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Fresh Fuel Measurements With the Differential Die-Away Self-Interrogation Instrument

The purpose of the Next Generation Safeguards Initiative (NGSI)-Spent Fuel (SF) Project is to strengthen the technical toolkit of safeguards inspectors and/or other interested parties. Thus the NGSI-SF team is working to achieve the following technical goals more easily and efficiently than in the past using nondestructive assay measurements of spent fuel assemblies: 1) verify the initial enrichment, burnup, and cooling time of facility declaration; 2) detect the diversion or replacement of pins; 3) estimate the plutonium mass; 4) estimate decay heat; and 5) determine the reactivity of spent fuel assemblies. The differential die-away self-interrogation (DDSI) instrument is one instrument that was assessed for years regarding its feasibility for robust, timely verification of spent fuel assemblies. The instrument was recently built and was tested using fresh fuel assemblies in a variety of configurations, including varying enrichment, neutron absorber content, and symmetry. The early die-away method, a multiplication determination method developed in simulation space, was successfully tested on the fresh fuel assembly data and determined multiplication with a root-mean-square (RMS) error of 2.9%. The experimental results were compared with MCNP simulations of the instrument as well. Low multiplication assemblies had agreement with an average RMS error of 0.2% in the singles count rate (i.e., total neutrons detected per second) and 3.4% in the doubles count rates (i.e., neutrons detected in coincidence per second). High-multiplication assemblies had agreement with an average RMS error of 4.1% in the singles and 13.3% in the doubles count rates.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2014

Determination of total plutonium content in spent nuclear fuel assemblies with the differential die-away self-interrogation instrument

As a part of the Next Generation Safeguards Initiative Spent Fuel project, we simulate the response of the Differential Die-away Self-Interrogation (DDSI) instrument to determine total elemental plutonium content in an assayed spent nuclear fuel assembly (SFA). We apply recently developed concepts that relate total plutonium mass with SFA multiplication and passive neutron count rate. In this work, the multiplication of the SFA is determined from the die-away time in the early time domain of the Rossi-Alpha distributions measured directly by the DDSI instrument. Here, we utilize MCNP to test the method against 44 pressurized water reactor SFAs from a simulated spent fuel library with a wide dynamic range of characteristic parameters such as initial enrichment, burnup, and cooling time. Under ideal conditions, discounting possible errors of a real world measurement, a root mean square agreement between true and determined total Pu mass of 2.1% is achieved.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

Euratom Fast Collar (EFC) Calibration Report

Neutron collars are used by international inspectorates to determine the amount of 235U in fresh LWR fuel assemblies. Standard neutron collars can operate in two modes: “fast” and “thermal”. In fast mode (using cadmium liners), thermal neutron are excluded from the assembly and the measurement results are not very sensitive to the presence of neutron poison loaded pins. In thermal mode, the thermal neutrons are affected by the presence of poison rods leading to significant effect, requiring corrections. These corrections depend on the declaration of the operator, reducing the independence of the inspectors’ measurements. The thermal mode signal is much higher than the fast mode signal and can give statistically acceptable results in ~600 seconds compared with ~1 hr for the fast mode. This report describes the calibration of a new fast neutron collar designed to use fast mode to reduce the effect of poison pins on verification measurements and with increased efficiency to reduce the measurement times to those normally used on inspection. The work was done in cooperation with the safeguards division of the European Commission and so the new collar is named the Euratom Fast Collar (EFC). The motivation and design work is presented in reference 2. The Monte Carlo simulations presented in reference 2 cover a larger parameter range than can be experimentally measured with the mock up assembly and so we base the performance on the simulation results, benchmarked to the measurements. The work presented here follows that of the “bible” of LWR fuel assembly measurements and uses the same mock-up assembly, with the same enriched, depleted and gadolinium poisoned fuel rods as were used in that work. Reference 1 describes how the measured count rate of the detector is corrected for AmLi source strength, electronic stability, efficiency, poison rods effects and heavy metal effects as well as other perturbing factors. These will be discussed below. INCC is the normal software that is used to collect and analyze neutron collar data. The results of this work have been formulated to fit into this existing INCC data analysis framework.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Integrated Test and Evaluation of 3He Replacement Technologies for Safeguards and Nonproliferation Applications – boron-based HLNC-B counter build

A full scale thermal neutron coincidence counter (High Level Neutron Counter – Boron: HLNB) was designed and built during FY12. Following successful functionality demonstration, initial performance evaluation using LANL available neutron and gamma-ray sources was performed during FY13. The results of this activity were shared with international community at the NNSA sponsored workshop on 3 He alternatives organized at LANL in June 2013. Field test of the HLNB is anticipated during FY14 pending funding approval. In addition to HLNB related activities, LANL supported and hosted experimental evaluation of Advanced Boron Uranium Neutron Collar (ABUNCL) designed by GE/RS and evaluated by PNNL. The evaluation involved use of LANL low enriched uranium (LEU) fresh fuel rods in a boiling water reactor (BWR) fuel arrangement. Details of the activities performed during FY13 are described in the following sections.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
DOE OSTI2013

Technical Assessment of the Passive Neutron Enrichment Meter (PNEM) for an Unattended Cylinder Verification Station (UCVS)

The International Atomic Energy Agency (IAEA) is exploring the potential roles of an Unattended Cylinder Verifications Station (UCVS) in a new generation of safeguards technology for uranium enrichment plants. The UCVS is envisioned to combine an operator accountancy scale, a nondestructive assay (NDA) system such as the Passive Neutron Enrichment Meter (PNEM), a cylinder identification system, and a surveillance system for verification of product, feed, and tails cylinders as well as continuity of knowledge at material balance area boundaries. The IAEA has identified several preliminary requirements and development questions for the UCVS. Specifically, the IAEA has identified the accuracy of the enrichment assay as the key metric for the NDA system with uncertainty targets of 3%, 6%, and 9% on product, feed, and tails cylinders, respectively. The NDA system should also provide full volume interrogation of the cylinders in order to ensure detection of partial defects within the cylinder. The development questions are concerned primarily with the sources and magnitude of the uncertainty and quantitative analysis of the interrogation depth and partial defect sensitivity. The objective of this report is to address these requirements and questions based on Monte Carlo modeling and field trial experience with the PNEM.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Differential Die-Away Self-Interrogation for Treaty Verification Applications (Final Report)

In this report, we summarize our experimental and simulation study of Differential Die-Away Self-Interrogation (DDSI) method used to assay 4 PuO 2 samples of almost identical isotopic composition with total Pu content ranging from 60-614g. With measured and calculated traditional neutron coincidence rates such as singles (S), doubles (D) and triples (T) we explore three different proposed DDSI signatures (D/S, T/S and D L /D F ) over a wide range of gating scenarios and analyze the sensitivity of individual observables to fissile content of the sample. We find that only the D L /D F observable is exclusively sensitive to the fissile content of sample, while D/S and T/S yield sensitivity to both fertile and fissile component of the sample. Based on the results of the Monte Carlo simulations, depending on the mass of the PuO 2 sample and considering 900s assay time with the Epithermal Neutron Multiplicity Counter (ENMC) we are able to reconstruct the fissile content with statistical uncertainty of 0.4-3.7% in case of D/S ratio, 1.1-4.3% in case of T/S ratio, and 4.9-34.3% in the case of the D L /D F .

Instrumentation Related to Nuclear Science & Techn↗
DOE OSTI2012

Summary of Project on Design and Development of a Safeguards Coincidence Counter Based on Boron-lined Proportional Detector Technology - High Level Neutron counter Boron (HLNB)

During the past several years, the demand for 3 He gas has far exceeded the gas supply. This shortage of 3 He gas is projected to continue into the foreseeable future. To continue to develop and deploy safeguards neutron detection systems, a viable, near-term, safeguards-specific, alternative to 3 He-based measurement technology must be found.

Nuclear Disarmament, Safeguards, & Physical Protec↗
DOE OSTI2012

Design and Development of a Safeguards Coincidence Counter Based on Boron-Lined Proportional Detector Technology - High Level Neutron counter Boron (HLNB)

High neutron detection efficiency is a requirement of correlated neutron measurements, therefore 3 He gas-filled proportional counters have long been the cornerstone of safeguards detection system designs. To address the decreased 3 He supply, several alternative detection technologies have been proposed and developed. In order for any technology to be viable for safeguards use, its performance characteristics essential for plutonium mass assay need to be evaluated and compared with a suitable 3 He-based reference. To address this need, LANL has developed an integrated test program for evaluation of 3 He replacement technologies in the safeguards context. The test program was formulated based on safeguards specific requirements derived from decades of experience with 3 He-based neutron counters.

Nuclear Disarmament, Safeguards, & Physical Protec↗
DOE OSTI2012

Status Report on the Passive Neutron Enrichment Meter (PNEM) for UF 6 Cylinder Assay

The Passive Neutron Enrichment Meter (PNEM) is a nondestructive assay (NDA) system being developed at Los Alamos National Laboratory (LANL). It was designed to determine 235 U mass and enrichment of uranium hexafluoride (UF 6 ) in product, feed, and tails cylinders (i.e., 30B and 48Y cylinders). These cylinders are found in the nuclear fuel cycle at uranium conversion, enrichment, and fuel fabrication facilities. The PNEM is a 3 He-based neutron detection system that consists of two briefcase-sized detector pods. A photograph of the system during characterization at LANL is shown in Fig. 1.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗