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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

UPF and Y-12 Criticality Accident Alarm System (CAAS) Radiation Testing Report

This report documents the experimental conditions and results for the testing of the Mirion Technologies CAAS-3S Criticality Accident Alarm System (CAAS) for the Y-12 National Security Complex (Y-12) and Uranium Processing Facility (UPF). The testing was conducted at the Godiva IV Burst Reactor at the National Criticality Experiments Research Center (NCERC) at the Nevada National Security Site (NNSS) during the week of January 11, 2021. The testing was conducted in accordance with 25774-QL-POA-JR00-00002-VDE-27.0, CAAS-3S Radiation Testing of Cabinet Components Test Plan. The tests subjected the CAAS-3S system to intense and short duration mixed neutron and gamma radiation fields and to high integrated radiation doses. The purpose of the test was to environmentally qualify various CAAS-3S components in a radiation environment. Successful completion of the tests was predicated on the collaborative efforts of several organizations. Sandia National Laboratory (SNL) and Lawrence Livermore National Laboratory (LLNL) provided dosimetry to estimate photon and neutron dose. Los Alamos National Laboratory (LANL) manages the NCERC facility, operated the Godiva IV reactor, and provided field support for CAAS-3S placement and communications interface for data acquisition systems supplied by Mirion Technologies. Throughout the test campaign, Y-12 and UPF personnel provided technical support in determining changes to the test schedule, as needed, interpretation of the results, and comparison between the measured dosimetry data and predicted results. Throughout the test campaign, Mirion personnel provided technical support in the operation of the CAAS-3S system itself.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2022

CAAS-3S Radiation Testing for Y-12 and UPF with Godiva-IV

The Y-12 National Security Complex and the Uranium Processing Facility (UPF) selected the Mirion CAAS-3S as the Criticality Accident Alarm System for UPF and for Y-12 facilities replacing their legacy CAAS as part of efforts to extend the facility lifespans. As part of this process, the CAAS-3S system was exposed to a high radiation dose and dose rate during reactor testing with the Godiva-IV fast burst reactor. The reactor testing was designed around preliminary analyses that determined Y-12 and UPF requirements, and simulations of the radiation field within the reactor facility were used to determine reactor operating parameters, CAAS equipment locations, and the design of a neutron shield wall. This paper presents the design and results of the testing, and discusses how the test results were interpreted by criticality safety engineers at Y-12 and UPF.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Materials Data on CaAs by Materials Project

CaAs crystallizes in the orthorhombic Pbcn space group. The structure is two-dimensional and consists of two CaAs sheets oriented in the (0, 0, 1) direction. Ca2+ is bonded in a 5-coordinate geometry to five equivalent As2- atoms. There are a spread of Ca–As bond distances ranging from 2.92–3.17 Å. As2- is bonded in a 6-coordinate geometry to five equivalent Ca2+ and one As2- atom. The As–As bond length is 2.57 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CaAs by Materials Project

CaAs crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. there are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded in a 6-coordinate geometry to six As2- atoms. There are four shorter (3.00 Å) and two longer (3.03 Å) Ca–As bond lengths. In the second Ca2+ site, Ca2+ is bonded in a 6-coordinate geometry to six As2- atoms. There are two shorter (3.04 Å) and four longer (3.07 Å) Ca–As bond lengths. There are two inequivalent As2- sites. In the first As2- site, As2- is bonded in a 7-coordinate geometry to six Ca2+ and one As2- atom. The As–As bond length is 2.59 Å. In the second As2- site, As2- is bonded in a 7-coordinate geometry to six Ca2+ and one As2- atom. The As–As bond length is 2.54 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2022

CAAS-3S Radiation Testing for Y-12 and UPF with Godiva-IV

Goals: 1) Qualify the CAAS-3S system to a mixed-field radiation dose and dose rate, and 2) Extend the Y-12 Shielding MCNP Validation to rad-si. This paper represents the efforts of Y-12 and UPF personnel, and their interpretation of the test results.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

Experiments for SINBAD: Evaluation of Oak Ridge Health Physics Research Reactor Operation Data for CAAS Benchmark Creation [Slides]

This report was a real information preservation and dissemination work with a lot of legacy content that was found and used. There was an abundance of uncertainty, discrepancy, and contradictory information. Yet, a detailed, functional SCALE model was built, and the benchmark created is useful for shielding and CAAs validation work. Sulfur fluence C/E ratios are large (2 to 5), so different benchmark metrics were studied. Neutron fluence, element 57 dose, and other dosimetry responses at 3 meters C/E ratios are below 1.5 for bare and steel configurations. Additional promising metrics as dose per unit fluence and steel shield attenuation were computed.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2024

Pressure-induced polyamorphic transition in CaA l 2 O 4 glass

In situ high-pressure ultrasonic velocity measurements of CaAl 2 O 4 glass reveal abrupt irreversible discontinuities in the elastic wave velocities at ~8–10 GPa. Total structure factor and pair distribution functions measured by synchrotron x-ray diffraction show a rapid change in the intermediate range structure attributed to a rearrangement of calcium ions over this narrow pressure region. Atomistic models obtained from molecular dynamics simulations reveal that this intermediate range structure is explained by a transition of Ca–O void radius distribution from a bimodal distribution with peaks at ~2.1 and ~2.4 Å to a single distribution centered at ~2.1 Å. Further, these abrupt structural changes involving the rapid increase in elastic wave velocity are markedly different to the continuous transformations observed in conventional network-forming glasses, such as SiO 2 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

FY21 Progress of the Oak Ridge Health Physics Research Reactor CAAS Benchmark Evaluation [Slides]

The FY21 version of the evaluation, focusing on element 57 dose at 3 meters, was presented at the ICSBEP Technical Review Group meeting in October 2021 and was not accepted for 2022 publication in the handbook. The main issue was identified and replacement of the element 57 neutron dose benchmark metric by neutron fluence (closer to what was measured) is required. A subgroup was formed, confident for the updated neutron fluence evaluation to be accepted in the ICSBEP handbook. The updated evaluation will be presented again at the 2022 ICSBEP TRG for publication in the 2023 handbook.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2024

Godiva 4 CAAS Shielding Benchmark: Pre CED-3A Overview [Slides]

Thiis presentation shows the character of an integral experiment. It covers the question why Godiva 4? Additionally, this presentation touches on the IER 498 benchmark quantity, activities facilitated by IER 498, proposed CED-2 test matrix, and what happened during the IER 498’s gap year.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2021

Resolution of Tolerance Variations

The connector/adapter assembly (CAA) is one component of a higher-level assembly. A simplified representation of the CAA is illustrated in Figure 1. The location of each CAA is required to meet a specific positional requirement. Several CAAs have been measured and found to be out of tolerance. The connector and the adapter are welded to each other such that the cylindrical axes of the two components are coaxial. The positional tolerance condition requires that all points on the outer surface of the CAA must be within a defined maximum diameter, as illustrated in Figure 1. Two different methods have been developed to measure the CAA positions from coordinate measuring machine (CMM) data. One method (RevD) extrapolates the data from two circles approximately midway from the weld region to each end. The second method (RevF) measures points that are much closer to the actual ends.

42 ENGINEERING↗
DOE OSTI2023

Evaluation of Copper Chelation Therapy in a Transgenic Rat Model of Cerebral Amyloid Angiopathy

Cerebral amyloid angiopathy (CAA) is characterized by the accumulation of the amyloid β (Aβ) protein in blood vessels and leads to hemorrhages, strokes, and dementia in elderly individuals. Recent reports have shown elevated copper levels colocalized with vascular amyloid in human CAA and Alzheimer’s disease patients, which have been suggested to contribute to cytotoxicity through the formation of reactive oxygen species. Here, we treated a transgenic rat model of CAA (rTg-DI) with the copper-specific chelator, tetrathiomolybdate (TTM), via intraperitoneal (IP) administration for 6 months to determine if it could lower copper content in vascular amyloid deposits and modify CAA pathology. In this work, results showed that TTM treatment led to elevated Aβ load in the hippocampus of the rTg-DI rats and increased microbleeds in the wild type (WT) animals. X-ray fluorescence microscopy was performed to image the distribution of copper and revealed a surprising increase in copper colocalized with Aβ aggregates in TTM-treated rTg-DI rats. Unexpectedly, we also found an increase in the copper content in unaffected vessels of both rTg-DI and WT animals. These results show that IP administration of TTM was ineffective in removing copper from vascular Aβ aggregates in vivo and increased the development of disease pathology in CAA.

36 MATERIALS SCIENCE↗
DOE OSTI2020

The Need for a Maximum Intensity Accident in ANS 8-Series Standards

The Y-12 National Security Complex has installed one Criticality Accident Alarm System (CAAS) under the ANS 8.3 framework as a safety significant system, and is in the process of designing, installing, and qualifying another. As a safety significant system, the Y-12 CAAS is required to demonstrate that it is able to perform its function and actuate an alarm when exposed to the radiation from both a Minimum Accident of Concern and a maximum intensity accident. The ANS 8-series standards do not present a maximum accident to be considered, nor do they specify radiation tolerance requirements for the CAAS equipment, leading CAAS vendors to potentially use other standards that provide inadequate criteria. In this paper, the historical basis and need for a maximum intensity accident in the ANS standards is discussed, the fission rate of a maximum intensity accident is proposed, and the effects of this accident on CAAS analysis and the vendor’s equipment qualification are discussed.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2023

Criticality Accident Alarm System Modeling for the Uranium Processing Facility

The Criticality Accident Alarm System (CAAS) for the Uranium Processing Facility (UPF) provides coverage for two primary processing facilities. For UPF, detailed documentation and drawings of the design are readily available. While this design information allows for some CAAS modeling features to match the actual design with a high level of accuracy, assumptions and simplifications are necessary as it is unrealistic and unnecessary to replicate many aspects of the design. A set of modeling guidelines and techniques were used to develop consistency between the MCNP6 models. While ensuring conservatism, overly conservative choices must be avoided to demonstrate the minimum accident of concern can be detected. To ensure proper modeling choices were made for the final models, a group of parametric studies were performed to evaluate the impact on the dose rates detected at the individual detectors. Some of these modeling choices and/or associated parametric studies include: - Modeling the grid steel area above the detectors as homogeneous stainless steel and determining the impact on detectability with an increasing density. - Modeling the presence of equipment in close proximity to the CAAS detectors. - Determining an appropriate material density to represent miscellaneous items not specifically modeled. - Evaluating the impact of sprinkler activation. The results of UPF CAAS analyses show that the modeling assumptions made based on the detailed design and parametric studies are appropriate and demonstrate accurate yet conservative models have been developed for detecting minimum accident of concern within the UPF.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2023

ANS-8.3 Criteria and the Use of Electronic Personal Detectors as a Criticality Accident Alarm System [Slides]

Motivations for EPDs as a CAAS: Key features of the 2022 revision of ANS 8.3; Review of the relevant criteria in ANS-8.3 2022–How does (or could) an EPD based CAAS comply; Advantages & Disadvantages of Permanently Installed CAAS; Advantages & Disadvantages of EPD Based CAAS; Suggested Decision Criteria; Conclusions & Recommendations.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
DOE OSTI2020

The Need for a Maximum Intensity Accident in ANS 8-Series Standards

Y-12 has installed one CAAS system under the ANS 8.3 framework as a safety significant system, and is in the process of designing, installing, and qualifying another. As a safety significant system, the Y-12 CAAS is required to demonstrate that it is able to perform its function and actuate an alarm when exposed to the radiation from both a Minimum Accident of Concern and a maximum intensity accident. The ANS 8-series standards do not present a maximum accident to be considered, nor do they specify dose rate tolerance requirements, leading CAAS vendors to potentially use other standards that provide inadequate criteria. A maximum intensity accident is proposed, and the effects of this accident on CAAS analysis and the vendor’s equipment qualification are discussed

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗