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Technical Basis SAVY-4000® Series, 5.5G Container (Rev. 1)

The 5.5 Gallon (5.5G) SAVY-4000® nuclear material storage container is the latest in the SAVY-4000® series. The 5.5G is similar to that of a 1or 2Qt container in functionality with the exception of a larger volume deep drawn and spun form body achieved through increases in the depth and diameter of the container. Here, a technical basis using engineering equivalency analysis, calculation, and test data is presented to establish that the 5.5G SAVY-4000® Container is a DOE Manual 441.1-1 compliant container at a drop height of 9 feet (rather than the typical 12 ft of the other SAVY-4000® containers) and that a twenty-five year design life (as with the currently approved SAVY-4000® series) is justified.

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Measuring 3D Profilometry of SAVY-4000 Nuclear Material Storage Containers: Novacam TubeInspect Capabilities Report

The SAVY-4000 container series is a general-purpose interim storage container for nuclear materials, developed and maintained by Los Alamos National Laboratory (LANL). It is the first vented, general-use nuclear material container to be demonstrated as meeting the requirements outlined in DOE M 441.1-1, the Nuclear Material Packaging Manual. Due to the challenging radiation, thermal, and corrosive storage conditions that the SAVY containers must endure, continuous surveillance techniques are employed to ensure the containers meet all safety standards and specifications. These inspections are typically performed by human operators, who check for issues such as corrosion, O-ring deterioration, corrosion, filter integrity, and potential manufacturing defects. However, human inspections alone are not sufficient, and automated inspection technologies, such as the ATIS system, as well as other automated systems are also utilized. The MicroCam TubeInspect, developed by Novacam Technologies Inc., is designed to address the challenges of understanding how manufacturing variations in the SAVY-4000 container series may affect performance. It is a 3D profilometry measurement system that enables detailed analysis of surface features, including defects, surface roughness, and manufacturing variations. This advanced tool significantly enhances rapid surveillance techniques for both pristine and used containers. In this study, container properties such as surface roughness, thickness, and geometric attributes like circularity are measured for SAVY-4000 containers. Artificially corroded or dented containers are examined to demonstrate the MicroCam's ability to quantify defects. A sensitivity analysis is also conducted, comparing the MicroCam results to those obtained using more precise instruments such as confocal microscopy. This comparison aims to provide valuable insights into container quality, durability, and potential improvements in manufacturing processes.

42 ENGINEERING↗

Framework development for a SAVY-4000 nuclear material storage container structural integrity surveillance tool

Here, this work presents the preliminary design of an automated surveillance tool to assess the health of SAVY-4000 nuclear material storage containers. This tool is designed by training several machine learning (ML) regression models to predict maximum residual stress in plain dents on the container sidewall. The model is trained on an experimentally validated Finite Element Analysis (FEA) model built in Abaqus FEA. The accuracy of each ML model is compared. The potential for application as well as model shortcomings are assessed. Necessary FEA model improvements are outlined and the various ML models are proposed.

36 MATERIALS SCIENCE↗

Evaluating Corrosion Effects on the Stainless Steel Components of the SAVY-4000/Hagan Nuclear Material Storage Containers: FY2022 Update

This report summarizes the work completed and underway for the Corrosion Working Group (CWG) for FY2022 in support of evaluating a greater than a 15 year design life for the SAVY4000. The CWG meets on an as needed basis to review new work, results or information regarding the corrosion of SAVY-4000 and Hagan nuclear material storage containers. The goal when analyzing corrosion is to develop a design life appropriate for the containers and to identify when a container should be removed from service. There are many parallel efforts associated with identifying and extending the service life of nuclear material storage containers. This report includes information from research and development efforts to address the lifetime. The CWG is closely related to surveillance activities and continues to play a role in identification of issues and paths forward for analysis of surveillance containers. This work summarizes the completed tasks for FY22 of the CWG while keeping in mind that some efforts continue into future years. Brief summaries of identified new avenues of work have been identified for FY23.

36 MATERIALS SCIENCE↗

NMPWG Discussion on - Tracking Initial SAVY-4000 Population and Lifetime Extensions Across the DOE Complex [Slides]

As part of LANL's SAVY-4000 Lifetime Extension efforts, the question of "when does a SAVY's life start?" was posed. The unfortunate answer that can be agreed upon is to start the life based on the serial number which includes month and date of manufacture. For example - 012405025 was a 5QT container produced in January of 2024. This is not the most efficient way to track age of a container if extended lifetimes and usage are desired. Other possibilities include: Tracking on first-use date (date it was loaded); Tracking when it was sold from the warehouse to an operating group for use; Tracing the amount of time nuclear material is within the container (LANMAS transaction histories).

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Corrosion Analysis of 121103072 (SAVY-4000)

A surveillance feedlist for fiscal year (FY) 2022 was developed with the intent to target containers with contents known to generate corrosive gasses. One SAVY-4000 (hereafter “SAVY”) container with a serial number 121103072 was selected due to the reasonable wattage and known molten salt extraction (MSE) material corrosive behavior. The material was measured at 3.08 W with approximately 200 g of material placed inside of the SAVY for 6.07 years. The inner packaging configuration included a ¼ Qt stainless steel slip top inner container and a sPVC bag-out bag enclosing the inner container. Visual observations of the container during retrieval revealed several concerning features on the exterior of the container, notably on the lid. Fig. 1 shows the container lid along with an inset image further magnifying the features of interest. The corroded tamper indicating device (TID) wire and the corroded radioactive material tag wire indicated that corrosive gas species for steel were produced during storage. Although the TID wire and rad tag wire are not the same composition as the SAVY body and lid, these are often used as an indicator of potential corrosion inside of the SAVY container. The oxide residing inside of the filter holes and significant buildup around one hole provided further evidence supporting the presence of corrosive species inside of the container.

36 MATERIALS SCIENCE↗

SAVY-4000 Lifetime Extension Overview for FY23

The SAVY-4000 (hereafter “SAVY) was granted a 15 year design life as of June 11, 2019. Since that time, a concerted effort to evaluate the SAVY lifetime beyond 15 years initiated. Several key gaps in knowledge were identified by subject matter expert reviewers across the complex, along with testing that should be included or addressed in the next technical basis. While surveillance has not fundamentally changed since the last life extension, many key techniques have since been identified as necessary to evaluate key container performance requirements not addressed previously (i.e. drop qualification release rate). FY23 provided an opportunity to establish the groundwork for the development of those key techniques that aid in addressing DOE Manual 441.1-1 (hereafter “Manual”) requirements for safe storage of nuclear material.

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Overview of SAVY-4000 Lifetime Extension Activities in Fiscal Year 2024

This report provides an overview of activities engaged in during the 2024 fiscal year in support of the SAVY-4000 (hereafter “SAVY”) lifetime extension. As the final full year prior to the submittal of the technical basis, efforts were made to assess the current understanding regarding SAVY degradation in service as well as any knowledge that provided a more substantive view of the challenges that SAVYs face in storage. Close coordination with the stakeholders (i.e. LANL program office) ensured alignment with expectations regarding timelines for the remainder of the activities supporting the technical basis document for the lifetime extension request.

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Full Submersion Water Testing of SAVY-4000 Nuclear Material Storage Containers

SAVY-4000 (SAVY) containers are the primary container used at Technical Area (TA) TA-55 plutonium facility for the prevention of water ingress to mitigate against a criticality event. The basis for water resistance of these containers has long been attributed to the Polytetrafluoroethylene (PTFE) membrane that is assembled on the outermost surface of the filter assembly. On August 22nd a test of a container used inside of a glovebox was performed that brought into question this long-standing-basis. This test was performed by inverting a SAVY-lid onto a specialized piece of equipment for evaluating the integrity of the PTFE membrane. During the test water was observed passing through the filter indicating that the filter membrane was no longer preventing the ingress of water through the filter. The assumption after making this observation was that alpha-particles were rapidly degrading the membrane creating a leak path through the underlying aluminosilicate media (Fiberfrax®). The apparatus used was designed to only test the lid rather than the entire SAVY assembly. A test plan, PA-PLAN-01921, was developed to investigate whether a fully assembled container with a fully degraded PTFE membrane would be capable of meeting the criteria defined in PA-RD-1009 of not allowing more than 200 ml of water to enter the container with a water column of 6-inches applied over a 2-hour period. This report provides the results of the testing performed against PA-PLAN-01921.

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Technical Basis Update for the Design Life Extension of the SAVY-4000® Series of Containers

This technical basis update focuses on the design life of the SAVY-4000® (hereafter “SAVY”) series of nuclear material storage container (e.g., used to store, transport, and handle special nuclear material outside of a glovebox), previously approved under DOE Manual 441.1-1, Nuclear Material Packaging Manual. The SAVY is approved for storing all authorized contents for a period of 15 years. The lifetime extension technical basis is established on the compiled technical data from the on-going SAVY and Hagan surveillance programs, destructive analysis results, accelerated aging studies, and performance testing, in line with the regulatory rigor of DOE M441.1-1.

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SAVY-4000 Finite-Element Drop Test Analysis

PFE Auxiliary Systems conducted drop testing on SAVY-4000 containers to evaluate structural response under 12-foot drop conditions. In support of that effort, a finite-element modeling capability was developed to simulate drop response across multiple container sizes and impact orientations. The purpose of this work was to provide a consistent analysis framework that could support interpretation of testing, compare response trends across multiple configurations, and generate quantities of interest for later comparison with experimental data. More broadly, the analysis and testing were intended to assess whether the containers continued to perform their primary function after a 12-foot drop, namely maintaining structural integrity and containment of the contents. The modeling approach combined an implicit preload analysis with an explicit drop simulation so that each drop event began from a mechanically realistic assembled condition, including compression of the silicone O-ring. Separate models were developed for 2-quart, 5-quart, 12-quart, and 10-gallon containers. The results were evaluated in terms of strain-gauge response, collar-lid gap behavior, and accumulated plastic strain. In addition, parametric studies were performed on the 2-quart container to assess sensitivity to O-ring stiffness, friction, canister thickness, geometry tolerance, and mesh density. The simulations showed that predicted drop responses depended strongly on both container size and drop orientation. Gap metrics identified cases in which the predicted collar-lid opening exceeded the nominal O-ring cross-section threshold, while plastic strain metrics identified localized regions of elevated permanent deformation. Parametric studies showed that the predicted response was especially sensitive to the assumed O-ring stiffness and contact friction, while the geometry tolerance study produced smaller changes in the cases examined. The main value of this work was that it established a repeatable modeling and simulation workflow to support drop-test implementation, evaluate effects of future configuration changes, and understand modeling assumptions that most influenced predicted response. At the current stage, the results were viewed as preliminary model predictions rather than validated predictions. The next step would be to compare drop-test data to the model so that predictive values of the workflow could be refined and used with greater confidence to assess whether the containers maintained structural integrity and containment of the contents after a 12-foot drop.

42 ENGINEERING↗

Laser Confocal Microscopy Uncertainty Quantification Study

At Los Alamos National Laboratory (LANL), the Storage Safety and Engineering (SSE) team completes annual surveillance on a subset of in-use interim nuclear material storage containers in fulfilment of requirements outlined in DOE Manual M 441.1-1. The containers are selected through several methods, such as subject matter expert judgement, random selection, and trending items. Following these selections, the SSE team has the capacity to complete surveillance on 15-20 containers each fiscal year, composed of a combination of SAVY-4000 and Hagan storage containers. Through previous work, the stainless-steel components of the containers have been identified as life limiting components, with an emphasis on the thin-walled bodies. The team is focused on understanding the extent of general and pitting corrosion, due to observations of extensive corrosion from stored contents and bag-out-bag degradation. Quantifying corrosion effects on the thin-walled stainless steel container bodies, and understanding potential impacts to the respective design release rates and design qualification release rates is paramount to the team. To date, destructive examination (DE) has proven to be the most insightful method for developing an understanding on the extent of corrosion on used containers. To standardize this process, the SSE team developed a destructive examination guide for analyzing stainless steel components of the containers. Corroded containers of interest are identified during surveillance activities and set aside for sectioning and characterization. Following sectioning, a major step in the DE workflow is the utilization of laser confocal microscopy for scanning corroded samples of interest and extracting data on pits, such as count, depth, and equivalent diameter. Adhering to the techniques outlined in the DE guide, analysis has been completed on two Hagans and one SAVY-4000 container, with the maximum pit depth recorded as 139.1 ± 22.82 μm on a 17.5 year old Hagan. The findings from the completed destructive examinations will be utilized to support lifetime extension efforts of the SAVY-4000 as the team can better estimate corrosion rates and effects over time based on stored contents and age. Due to the implications of observing extreme pit depths that approach the nominal container body thickness of .0299 inches (0.759 mm) or minimum container thickness of 0.236” (0.6 mm), high confidence in the LCM measurements is desired. Through testing outlined in, it was concluded that the total error ascribed to the 20x objective when conducting large image mapping on the Keyence VK-X3050 laser confocal microscope (LCM) relative to a 50x objective (reference) is 16.4% (± 8.73%). For shallow features on the order of pristine SAVY surface defects (i.e. 5 μm), this uncertainty is appropriate. However, this conservative estimate of total error poses a fundamental concern for pit depths that approach the thickness of the measured samples. That is, with the measurement uncertainty currently employed on all measurements, the LCM would be unable to resolve if a pit with a depth of 515 μm is through wall. Standard step height samples were procured and used in the present study to assess the resolution and repeatability of height measurements. Understanding the resolution and repeatability of height measurements was the first focus of the team as it relates directly to pit depth, which is of primary concern. Calibration gratings were procured to evaluate the resolution and repeatability of measurements in the X and Y axes of the LCM stage. The results of the depth uncertainty study were conducted first and presented in the subsequent sections. The planar uncertainty study is appended to the depth study with conclusions from both summarized at the end of the report.

36 MATERIALS SCIENCE↗

SAVY O-ring characterization for lifetime extension

Los Alamos National Laboratory and Nuclear Filter Technology, Inc. developed the SAVY-4000 nuclear material storage container, named after the designers Stone, Anderson, Viers, and Yarbro. The SAVY 4000 meets the requirements of Department of Energy (DOE) M 441.1-1,2 Nuclear Material Packaging Manual, to protect workers who handle nuclear materials against radiation exposures resulting from the leakage of stored materials. The SAVY-4000 is an innovative and creative design: it can be opened and closed in a few seconds without using torque wrenches and instead only a tire iron or equivalent prying tool; has a built-in, fire-rated filter that prevents the build-up of hydrogen gas yet retains 99.97% of plutonium particulates at 200 ACCM rated flow; and prevents the release of stored materials upon a 12- foot drop.

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L4-3 Developing DOE M441.1-1 Compliant Container Components: Filter Cup Experimental Fixture Test Data Verification

This document serves to provide technical documentation and justification for using the Filter Cup Experimental Fixture (FCEP) for filter efficiency and pressure drop testing in the Enhanced Filter Test System (EFTS). This document assumes that the reader has prior knowledge related to both of these systems, as well as the SAVY-4000® nuclear material container series filter technology.

42 ENGINEERING↗

Lifetime extension drop-test of real-world corroded 5 Quart Hagan nuclear material storage container

A 5Qt Hagan container with a 20-year history of nuclear material storage was challenged with three successive drop tests at a height of 3.7 meters. The total mass of the test package was 12.1 kg. The 1st and 2nd drop tests (center of gravity over the container bottom corner but 180 degrees apart on the container bottom face) passed the pre- and post- impact helium leak criterion at less than 1.00E-6 atm-cc/sec (ambient cubic centimeters per second). The 3rd and final test (center of gravity over top corner) failed with a post-impact gross leak of 1.1E-1 atmcc/sec. The RRFMC (Respirable Release Fraction Measurement Chamber) is a drop tower test system that is critical for the sustainability of the SAVY-4000™ series and Hagan-type (NFT Inc. Golden CO) nuclear material storage containers. These are the primary in-use nuclear material storage container types at the Los Alamos National Laboratory TA-55 facility. Results are presented to expand the technical knowledge basis for container lifetime, regarding actual exposure to corrosive gas species on the container inner surfaces. The primary source of general corrosion throughout the container is gaseous hydrogen chloride (HCl). This gas is generated by the degradation of the polyvinylchloride (PVC) bag-out bag. Additionally, in most cases, the nuclear material itself also releases HCl gas (due to residual chemical components associated with the material formation). The RRFMC drop tower gives the end-user the ability record and analyze high-speed video and photography and if needed aerosol mass release measurements. In this report the principal issue is the physical deformation of the 5Qt Hagan container. There were no mass release experiments of test aerosol mass in the present study.

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