Engineering topics

Nicholson, James C.

Publications and source records attributed to Nicholson, James C..

13 records

DOE OSTI2024

Malachite green based radio-chromic compounds and radiation sensing systems incorporating the compounds

Derivatized malachite green leuco dyes for use in radio-chromic systems are described. The dyes have the following structure: in which Ar is a substituted phenyl or thiophene ring in which at least one substitution of the Ar ring is not ortho to the bond between the ring and the linking carbon, and in which R 1 , R 2 , R 3 , and R 4 are independently selected from methyl, alkyl, or alkyl halide. The systems include the dyes in conjunction with an activator, e.g., a halogenated activator, and a carrier, e.g., a fluid carrier or an encapsulating polymeric matrix.

Washington, II, Aaron L.↗

DOE OSTI2022

Radiological Considerations Supporting the American Medical Isotope Producer Niowave

This report provides a summary of work performed by Savannah River National Laboratory (SRNL) during FY22 in support of Niowave, an American Medical Isotope Production (AMIP) facility. SRNL served in a technical support role, funded by NA-231, supporting Niowave in the beginning of non radiological functional testing of their airport facility in FY22. Through this agreement, SRNL provides Niowave access to subject matter experts (SMEs) for questions that may arise during the drafting of engineering plans, facility policies, and/or response procedures. This report summarizes discussions between SRNL and Niowave about guidance concerning issues with the floor of the hot cells, dispersible removable contamination (beta emitting fission product), hot cell operation specifically utilization of cameras or mirrors, and the process for removing contaminated waste from the hot cell. Lessons learned and other various resources provided to Niowave by SRNL during FY22 are referenced in this report. This work was funded through NNSA’s Office of Material Management and Minimization, Conversion Office (NA-231).

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2020

Advancement of Commercial Intumescent Expanding Foams for Deactivation and Decommissioning in the Nuclear Sector - 20198

Florida International University (FIU), in collaboration with The Department of Energy's Office of Environmental Management (DOE-EM), Savannah River National Laboratory (SRNL), and sites across the Savannah River complex, have identified an operational requirement for a fixative technology that is intended to immobilize and/or isolate residual contamination within a 3-dimensional space. Fixation of radiological contamination can reduce worker risk and mitigate potentially hazardous conditions, however nearly every marketed contamination fixative has been found to be flammable; a significant concern in radiological facilities. Coupled with this, industry fixatives are normally used as a thin coating which can present problems when attempting to stabilize irregular geometry or areas that are difficult to access whilst ensuring full coverage. The technical evaluation and advancement of commercial-off-the-shelf (COTS) polyurethane foams has yielded a down-selected candidate that shows potential in meeting the requirements to support deactivation and decommissioning activities. Several performance criteria have been established and tested to progress the technology readiness level towards an active field demonstration (TRL-7). Such criteria include: mechanical failure limits, adhesive and cohesive properties, thermal/fire resilience, determining thermal behavior, ability to immobilize contamination, and a means of non-destructive evaluation of applications. The test scenario examined was targeted towards an application for decommissioning nuclear pipework, in which the down-selected polyurethane foam would act as a barrier to segregate pipework and mitigate the potential for release during cutting, packaging, and storage operations. Testing carried out at SRNL included: mechanical evaluation of tensile, compressive, and adhesion strength by dynamic mechanical analysis (DMA), as well as thermogravimetric analysis (TGA). FIU examined the foam's fixative properties by utilizing phosphorescent europium-dysprosium doped strontium aluminate powder to investigating the extent to which contamination can be immobilized. FIU has also exploited previous successes in the field of intumescent technologies to assess the down-selected foam's tolerance to an extreme fire scenario, while maintaining the ability to effectively mitigate a contamination release. Parallel to this, extensive thermal investigations were carried out to determine the upper boundary of anticipated heat generation during the curing process as heat generation has the potential to compromise rubber parts of contaminated enclosures. These investigations subsequently yielded a promising method for a non-destructive application evaluation by means of infrared thermography. Utilizing the high sensitivity of modern IR cameras, coupled with the heat generated during the curing process of the polyurethane foam, FIU has been exploring the concept of monitoring the external pipe surface for indications of an irregular or abnormal application, thus informing operational decision making. The testing carried out utilized several current 'best fit' ASTM standards, which serve as helpful guidelines for testing, however, a precise definition of the operational parameters and requirements is still necessary. With continued collaboration with SRNL, FIU aims refine said definitions and develop new standards by which this, and other decommissioning technologies, can be accredited by relevant standards based testing. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2020

Investigation of Polyurethane and Fire-Retardant Foams as a Radiological Contamination Fixatives - 20202

Fixation of radiological contamination in decommissioning and deactivation can reduce worker risk, and mitigate potentially hazardous conditions; however, nearly every marketed contamination fixative has been found to be flammable, a significant concern in radiological facilities. Coupled with this, industry fixatives are normally used as a thin coating which can present problems when attempting to stabilize irregular void spaces or areas that are difficult to access and ensure full coverage. To this end, Savannah River National Laboratory (SRNL), in conjunction with Florida International University (FIU), have begun investigating the applicability of polyurethane based foaming materials, which will expand to fill a given asymmetric volume and provide fire retardancy to ensure no release of contamination in the event of a facility fire. Commercial foams undergo exothermic reactions resulting in gaseous release that subsequently causes the curing foam material to expand. Heat generation during curing can potentially compromise rubber parts of an enclosure, a significant concern in nuclear facilities. To mitigate large body heat generation, SRNL has also examined multiple layering of the material to ensure compatibility of the curing material with a previously cured body of the same material. Environmental studies were also completed in order to determine the influence on polyurethane based foams curing process. These studies showed that nearly half of the materials tested delaminated from a cured body of the same material, a property not discussed in commercially available documentation on the products. Of note was the compatibility of the foaming material with the substrate, depending on the type material that the foam was cured in/on, significant delamination could occur. Mechanical testing via tensile pull tester, dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA) was also performed. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2020

Adhesion Capabilities of Permanent Foaming Fixatives for Deactivation and Decommissioning Activities - 20308

Florida International University's Applied Research Center and the Department of Energy's Savannah River National Laboratory are examining various mechanical properties of intumescent rigid polyurethane foams in order to be used as a permanent foaming fixative. Intumescent polyurethane foams are favored more than non-intumescent polyurethane foams due to their ability to mitigate flame and smoke propagation when exposed to a fire. As a consequence, this ability, known as intumescing, will allow fire personnel ample time to arrive at a scene. Due to sites being dormant for many decades before the final decontamination stages, the likelihood of a fire remains high. Adhesion properties will ensure quality immobilization performance. The analysis consisted of evaluating tensile adhesion strengths on a variety of commercial-off-the-shelf polyurethane (PU) foams. The foams consisted of intumescent and a combination of flexible and rigid foams. The goal was to down select the rigid foams out of the group in terms of tensile adhesion performance. The ensuing analysis was to conduct shear adhesion testing on the rigid foams in an operational volume with one of the rigid foams being intumescent. This approach helped down select the intumescent rigid foam in an adhesion and operational sense. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2019

Characterizing The Mechanical Properties of Polyurethane Foams

The implementation of polyurethane foams as a permanent fixative for radioactive contamination is currently being examined within the DOE complex for its use in decontamination and decommissioning (D&D) activities. The work involving the implementation of permanent foaming fixatives in a decontamination scenario would include the filling of structures with large voids, such as gloveboxes, pipes, and tanks, where the use of a traditional 2D paint fixative is impractical or unsafe. The mechanical performance of such commercial off the shelf permanent foaming fixatives is uncharacterized with response to harsh environmental conditions often found in nuclear facilities that are undergoing D&D. To this end, SRNL embarked on a mechanical characterization of 6 polyurethane foams, 4 of which were considered flexible and 2 of which were rigid. Two tests were performed on these foams; a tensile tearing test and a compressive test, both of which were strictly guided by ASTM standards. It was found that in both harsh compressive and tensile scenarios, the Hilti brand foam outperformed all other foams, having a peak stress value higher than the closest competitor by a factor of 2.3, and a compressive yield point that was larger than the closest competitor by a factor of 1.4.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Alpha/beta radiation shielding materials

Alpha/beta radiation barrier materials and structures formed to include the barrier materials are described. Barrier materials include a matrix and particulate materials contained in the matrix. The particulates include alpha/beta radiation absorbers. Alpha/beta radiation absorbers of the barrier materials can be molecular, particulates, or defined nanostructures that are capable of absorbing incident alpha/beta particle energies. Matrix materials can include organic or inorganic materials including thermoplastic polymers, thermoset polymers, glasses, ceramics, etc.

36 MATERIALS SCIENCE↗

DOE OSTI2019

International Standards as Critical Enablers to Development and Diffusion of D and D Technologies - 19372

The U.S. Department of Energy's Office of Environmental Management (DOE EM) has taken a leading role in investing in the research and development (R and D) of critical technologies to support the safe and efficient decommissioning of legacy nuclear facilities. In order to facilitate the complex-wide deployment and adoption of those technologies from the laboratory to end users, and to maximize return on investment of government-sponsored R and D projects, DOE EM proactively solicits and evaluates initiatives intended to enhance achievement of these goals. One such case study emerged and involved the successful deployment of an intumescent fixative technology in support of the SRS 235-F PuFF Facility Risk Reduction Program. A detailed analysis confirmed that a critical enabler and key contributor to this effort was a deliberate, methodical approach to leverage an international, consensus-based standards organization from the onset. There is a substantial body of literature that supports the crucial role of standards in technology programs across all phases of development - from concept, to deployment, to large-scale diffusion - in other industries. Formal standards are the result of a consensual negotiation process carried out by producers, regulators, end users and other interested stakeholders in a voluntary process within standardization organizations (WTO, 2011). Therefore, standard setting is often viewed as a self-regulatory process (Gupta and Lad, 1983), and can often yield better acceptance of technologies in certain industries, particularly if those standards are further referenced in government directives and regulations. This analysis connects several theoretical concepts: information asymmetry, risk adverse markets, and technology diffusion. It is complimented by some initial, rudimentary survey results in a burgeoning academic study conducted by the author, and reinforced by the aforementioned case study on the deployment of a fixative technology at the SRS 235-F PuFF Facility. The importance of managing a holistic technology development program that focuses on not just the technical aspects of the technology itself, but the critical enablers as well, is emphasized. This effort has direct application to potentially enhancing DOE EM technology development programs across the complex. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2019

Particle Loading Dynamics of SRNL Electrostatic Particle Collectors - 19398

The Department of Energy is interested in decontamination methods and tools for the removal of airborne radioactive particulate from facilities prior to decommissioning. Electrostatic particle collectors (EPCs) have historically been used industrially to scrub particles from air streams for large scale operations, and Savannah River National Laboratory (SRNL) researchers have expanded on the fundamental collection capabilities of EPCs to develop unique samplers focused on particulate effluent collection. One distinct advantage of an electrostatic particle collection over filtration or inertial impaction-based methods is the low pressure drop associated with prolonged use of EPCs. Electrostatic particle collectors previously developed by SRNL have proven effective in the collection of atmospheric aerosols in multiple field trials, and their applicability as a decontamination method for airborne particulates. Initial experiments using aerosolized NaCl were performed to determine EPC collection efficiencies, the times required to achieve a desired particle loading, and the size distribution of collected particulates. The amount of NaCl collected on Si substrates was found to increase linearly with time (∼ 2 mg per hour) and showed little sign of change after 24 hours of collection. Experiments showed that NaCl, or a similar aerosol, would likely continue to collect unperturbed until physical limitations within the EPC are reached. Collection efficiencies (i.e., the number of particles collected vs. the number of particles entering the EPC) were calculated independently using an assessment scheme based on Particle Depletion Dynamics (PDD) and by Computer Controlled Scanning Electron Microscope (CCSEM) analysis of collection substrates for a range of particle sizes. For the ACE 2.0 with a corona voltage of 15 kV, collection efficiencies were determined using PDD to be 54, 29, and 13% for the flow rates 100, 300, and 490 L/min respectively. While CCSEM data suggests a very high collection efficiency for the MiniACE, the static sampling rate of 28.1 L/min (1 ft{sup 3}/min) was found to be too low volume for PDD to provide statistically meaningful data. Number density maps of NaCl particles detected via CCSEM revealed that particles are preferentially collected near the EPC inlet (i.e., opposite the direction of airflow) when using slower flow rates. Particles collected using higher flow rates (e.g., 300 and 490 L/min) were collected more evenly across the substrate. When segregated by size, smaller (e.g., 200-500 nm) particles are collected evenly across the collection substrates. As particle sizes increase they are collected preferentially near the EPC inlet, but not in sufficient quantity to obstruct airflow and hinder long-term operations. Subsequent deployment of the SRNL developed system into plutonium-238 contaminated hot cells will be performed at Savannah River Site Building 235-F. Presented in this work are the testing and considerations utilized by SRNL to show this technique as a viable means of rapidly decontaminating airborne contaminated areas. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2019

Stabilization of Residual Contamination with Alternative Materials - 19404

Since 2015, Savannah River National Laboratory (SRNL) in conjunction with Florida International University (FIU) have been investigating the applicability of intumescent coatings as radiological contamination fixatives for stabilization of residual materials after decontamination efforts have concluded. Intumescent coatings are designed to prevent heat transfer to a protected substrate and are typically used in both the aerospace industry to protect components from thermal shock and in building design to protect building joints that may fail in the event of a fire. For this work, these materials are examined for their ability to reduce worker risk by fixating residual contamination and lower the impact of a release in a scenario that breaches containment of a contaminated building and subsequently induces a large-scale fire by crediting their fire-retardant attributes. Initial studies of intumescent coatings and commercial fixatives included performance in direct flame, varied environmental conditions (20-110 F or -6.67 C, 10-95% relative humidity), adhesion studies to stainless steel after curing in varied environmental conditions, and radiological exposure. Of all the materials tested, many were found to be inadequate in one or more of these areas. These materials failed in one or more of three characteristic ways: 1) through delamination at reduced temperatures (≤40 F or 4.44 C) or from even moderate handling, 2) melting off the substrate at elevated temperatures (≥90 F or 32.22 C), 3) proving to be flammable and promote smoke propagation. Failure in these ways results in the potential for a subsequent release of the fixated contamination in the event of water presence/absence or direct flame. Using these results as a platform for the best in class identified material that did not experience failure in any of these tests, SRNL and FIU targeted the plutonium-238 contaminated hot cells within Savannah River Site (SRS) Building 235-F as a characteristic test bed to benchmark an intumescent coating used as a contaminant fixative. Through discussion with the SRS 235-F Risk Reduction personnel, appropriate hazards and performance metrics were discussed and a cold demonstration was performed in a hot cell mockup located at SRS. The application methods were proven functional in the cold mock up, and these intumescent coatings were subsequently utilized in the Savannah River Site Building 235-F's Plutonium Fuel Form (PuFF) Facility to aid in stabilization of plutonium-238 in both a contaminated hot cell and Entry Hood in September 2018. Presented in this work is the overview of the application process, associated working considerations for introduction of equipment and materials into the facility, lessons learned, and lifetime monitoring data to date. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2018

International Standards Development and Its Role in Transitioning D and D Technologies to Deployment - 18315

As the need to perform deactivation and decommissioning (D and D) of the most challenging nuclear facilities worldwide is growing, facilitating the integration of state-of-the-art, cutting edge technologies will be critically important to safely, effectively, and efficiently complete this mission. However, end users in the field face significant obstacles to integrating new technologies into cleanup initiatives. By leveraging the development of international standards and testing protocols, the risks associated with implementing new technologies can be mitigated and further support the need to update existing directives and guidance handbooks to account for the tremendous recent advancements in technology development. The American Society for Testing and Materials (ASTM) International's E10.03 Subcommittee on Radiological Protection for D and D of Nuclear Facilities and Components has begun the development of standard specifications and uniform testing protocols designed to support the nuclear industry's testing and evaluation requirements for D and D technologies. The vision of the E10.03 Subcommittee is to promulgate operationally relevant, uniform testing protocols that can be leveraged by the various technology innovation and development programs across the nuclear environmental management community, and support decision makers and end users with common references in the selection and employment of those standards and associated technologies. These standards could also serve as the basis for updating existing directives and guidance documents such as the various DOE handbooks to better account for the role of cutting edge technology, and facilitate / expedite lab to market efforts that result in improved returns on investment (ROIs) for technology development programs. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2016

Dry Sintered Metal Coating of Halloysite Nanotubes

Halloysite nanotubes (HNTs) are a naturally-occurring aluminosilicate whose dimensions measure microns in length and tens of nanometers in diameter. Bonding defects between the alumina and silica lead to net negative and positive charges on the exterior and interior lumen, respectively. HNTs have been shown to enhance the material properties of polymer matrices and enable the sustained release of loaded chemicals, drugs, and growth factors. Due to the net charges, these nanotubes can also be readily coated in layered-depositions using the HNT exterior lumen’s net negative charge as the basis for assembly. These coatings are primarily done through wet chemical processes, the majority of which are limited in their use of desired chemicals, due to the polarity of the halloysite. Furthermore, this restriction in the type of chemicals used often requires the use of more toxic chemicals in place of greener options, and typically necessitates the use of a significantly longer chemical process to achieve the desired coating. In this study, we show that HNTs can be coated with metal acetylacetonates—compounds primarily employed in the synthesis of nanoparticles, as metal catalysts, and as NMR shift reagents—through a dry sintering process. This method was capable of thermally decaying the metal acetylacetonate, resulting in a free positively-charged metal ion that readily bonded to the negatively-charged HNT exterior, resulting in metallic coatings forming on the HNT surface. Our coating method may enable greater deposition of coated material onto these nanotubes as required for a desired application. Moreover, the use of chemical processes using toxic chemicals is not required, thus eliminating exposure

36 MATERIALS SCIENCE↗

DOE OSTI2016

Developing radiation tolerant polymer nanocomposites using C 60 as an additive

In nuclear facilities utilizing plutonium, polymeric materials are subjected to long-term, close-contact, and continuous α radiation exposure, which can lead to compounding material degradation and eventual failure. Herein we model the attenuation of α particles by linear-low-density polyethylene (LLDPE), polyvinyl alcohol (PVA) thin films, and C 60 using Monte Carlo N-Particle Extended (MCNPX) software. The degradation of these materials was investigated experimentally by irradiating them with a beam of α particles of 5.8 MeV energy at a tandem Van de Graaff accelerator delivering a dose rate of 2.95 × 10 6 rad s –1 over a 7.1 mm 2 sample area. Our development of a method to test α particle-induced material degradation using a tandem accelerator is significant as degradation from naturally occurring α sources (i.e. Pu, Am) occurs too slowly for these sources to be used in practical experiments. Our results show that PVA nanocomposites containing 5 wt% C 60 were found to withstand about 7 times the α dose of undoped PVA films before a puncture in the film was detected. When these films were adhered to a LLDPE sheet the dual layer polymer was capable of withstanding about 13 times the dose of LLDPE and nearly twice the dose of the doped PVA thin film alone. Doping polymers with C 60 is an attractive way to generate more durable, radiation tolerant materials without increasing the thickness of the material which would lead to greater waste for disposal. Furthermore, the results herein help to resolve a prevalent technical challenge faced in nuclear facilities that utilize polymeric materials for nuclear processing and disposal.

36 MATERIALS SCIENCE↗