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At least 1,639 records · Page 91
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

First Industrial Tests of a Drum Monitor Matrix Correction for the Fissile Mass Measurement in Large Volume Historic Metallic Residues with the Differential Die-away Technique

The fissile mass in radioactive waste drums filled with compacted metallic residues (spent fuel hulls and nozzles) produced at AREVA La Hague reprocessing plant is measured by neutron interrogation with the Differential Die-away measurement Technique (DDT. In the next years, old hulls and nozzles mixed with Ion-Exchange Resins will be measured. The ion-exchange resins increase neutron moderation in the matrix, compared to the waste measured in the current process. In this context, the Nuclear Measurement Laboratory (NML) of CEA Cadarache has studied a matrix effect correction method, based on a drum monitor ({sup 3}He proportional counter inside the measurement cavity). A previous study performed with the NML R and D measurement cell PROMETHEE 6 has shown the feasibility of method, and the capability of MCNP simulations to correctly reproduce experimental data and to assess the performances of the proposed correction. A next step of the study has focused on the performance assessment of the method on the industrial station using numerical simulation. A correlation between the prompt calibration coefficient of the {sup 239}Pu signal and the drum monitor signal was established using the MCNPX computer code and a fractional factorial experimental design composed of matrix parameters representative of the variation range of historical waste. Calculations have showed that the method allows the assay of the fissile mass with an uncertainty within a factor of 2, while the matrix effect without correction ranges on 2 decades. In this paper, we present and discuss the first experimental tests on the industrial ACC measurement system. A calculation vs. experiment benchmark has been achieved by performing dedicated calibration measurement with a representative drum and {sup 235}U samples. The preliminary comparison between calculation and experiment shows a satisfactory agreement for the drum monitor. The final objective of this work is to confirm the reliability of the modeling approach and the industrial feasibility of the method, which will be implemented on the industrial station for the measurement of historical wastes. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2023

Residual loss due to magnetic flux trapping in niobium superconducting microwave cavities

One of the significant source of radio frequency loss in superconducting microwave cavities is the trapped residual magnetic field during the cooldown due to the incomplete Messier effect. The sensitivity of flux trapping depends on the distribution of impurities, network of dislocations and defects which pin vortices. Recent advancement in cavity processing techniques resulted in very high quality factors with impurity doping, however the rf loss related to the flux trapping increases. High quality factor in SRF cavities is not only limited to particle accelerators but also emerging as an application to quantum computing and quantum information science. In this presentation, we present the results of measurements of flux trapping sensitivity on several 1.3 GHz elliptical accelerating cavities with different grain size, impurity content and surface preparations.

Dhakal, P.↗
DOE OSTI2015

Residual waste detection in HLW tanks - 15701

This research uses commercial sonar technology to monitor residual waste in the U.S. Department of Energy's (DOE) Hanford Site high-level-waste staging tanks, with primary focus on the detection and imaging of the settled solids at specified areas of interest along the tank surface within a limited amount of time. High-level waste (HLW) is generated at the US-DOE Hanford Site as a by-product from the processing of nuclear materials. Waste is currently stored in 177 underground carbon-steel waste tanks. Pulse jet mixers (PJM) are often used to break loose and suspend the solids that have settled at the bottom of the tanks. A typical tank can have 6-8 pulse tubes. The Solid Liquid Interface Monitor (SLIM) must be capable of measuring dynamic movements in Region 1 zone between each PJM cycle. SLIM was originally developed to map the sludge/supernate interface within the U.S. DOE Hanford Site's HLW tanks. SLIM is a dual-axis mechanically rotating sonar and consists of an acoustic transducer, rotation motor with gearbox, tilt motor, position reference sensor, and pressure balancing mechanisms and its associated deployment platform. The sonar gathers a swath of data in the horizontal plane and rotates the transducer through a programmed angle around the vertical axis. Oil-filled device. No user serviceable parts. No semiconductors. Hard anodized aluminum and polyurethane delrin. May be deployed in areas of significant radioactivity. Kaolin will be used during mixing operations in order to simulate the physical properties of the expected slurry. In order to reduce the amount of time needed to image and object, all settings were decreased to their minimal state. The low resolution settings provide insufficient data for the manufacturer's 3D profiler to compile a visible point cloud and much less to allow the meshing algorithm to work properly. Several filtering algorithms have been applied to each scan in order to remove erroneous spikes and ghosting effects. Data has been collected for the mixing process of kaolin. This data consists of scans executed while the pump was active and inactive. The imaging algorithm has also been used with data derived from scans of 3% or less of kaolin. Future work: Mixing of kaolin within an experimental tank will be conducted in order to simulate the settling time of the HLW within the tank. The same filtering algorithms will be applied to each of these scans to evaluate the SLIM's efficiency to image solids at the bottom of a tank through increasing volume of kaolin.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Molten Salt Oxidation of Ion Exchange and Oils in Carbonate Salts and Evaporator Residue - 16531

Molten Salt Oxidation is a well-studied and robust technology. Recently, renewed interest in the technology has been seen due to limitations on the use of incineration for hazardous and radioactive waste streams. The nuclear research center at Rez, near Prague, has been investigating a bench scale molten salt oxidation system to provide insight for the design of a pilot scale system to condition spent ion exchange resin and scintillator oils. The use of both an eutectic K/Na/Li carbonate salt and a simulated residue salt for liquid waste obtained from evaporated primary coolant of nuclear reactors was examined. In these studies the usable capacity of the salts were examined. Materials doped with surrogate radioisotopes were processed and the capture efficiency was measured. Corrosion of the reactor vessel is of significant engineering concern. Corrosion coupon tests were performed for Inconel HX and stainless steel. These tests provided corrosion rates to assist in design of pilot scale systems. While the bench scale reactor's detention time was too short to provide complete combustion, the values of emissions were tracked and showed an increase in the combustion efficiency at temperatures greater than 750 deg. C. A two part reactor has been designed and work is planned to continue to optimize the system. Additionally, further work has examined the final conditioning of salt which has been saturated with radionuclides after processing organic waste streams A conceptual pilot plant has been designed to solidify radionuclide saturated salt into a form acceptable for repositories according to EU directives. Saturated salt is milled to a powder and immobilized in a matrix with a high percentage of waste loading. Both geo-polymer and polysiloxane matrices have been methods for low temperature immobilization. Conditioning in this manner decreases operating and capital costs when compared to current conditioning technologies and procedures utilized for high volume reduction factors of final waste forms. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Climatic Controls on Residual Contaminants Under Sustainable Remediation - 18699

We investigate the impact of climate change on residual contaminants in soil and groundwater under sustainable remediation. We illustrate seven climate change scenarios which mimic shifts in the precipitation regime as well as the failure of the source-zone cap. We evaluate different performance metrics including contaminant concentrations at multiple wells and export to a creek. The approach is demonstrated by simulating the tritium plume migration at the Savannah River Site F-Area, USA. The cap integrity is critical not only to reduce the well concentrations and export but also to reduce the uncertainty associated with the climatic variability. Sampling or in situ monitoring near the source zone is important for the early detection of plume mobility changes. Realistic hydrological models are necessary to evaluate the trade-offs (mobility vs dilution)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Cement Solidification of Residual Metal Oxide from Radioactive Waste

A lot of uranium contaminated soil and concrete waste is generated from the dismantlement of uranium conversion facilities. There are several disposal methods for radioactive materials such as regulation exemption, decontamination and long-term storage. It is necessary for us to achieve the permanent disposal of radioactive waste. The methods for solidifying radioactive waste include cement solidification, asphalt solidification, and polymer solidification. Cement solidification has several advantages such as well-known materials and technologies, various applications, and reasonable cost. On the contrary, it has certain disadvantages such as a large volume expansion of solidification for radioactive waste. Because cement solidification has excellent structural strength and a shielding effect, it is widely used for the permanent disposal of radioactive waste. Cement solidification operates as a barrier against the leaching of nuclides during radioactive waste disposal. To evaluate the criteria of KORAD (Korea Radioactive Waste Agency), integrity tests on the solidification of radioactive waste need to be performed. In this study, to inspect the criteria of KORAD, we carried out the cement solidification of residual metal oxide from radioactive waste. An integrity inspection such as the pressure strength, inundation, and leaching test on cement solidification was performed. We also analyzed the experimental results according to the criteria of KORAD. The calculation of the leachability index on the primary and secondary cement solidification for leaching detection of nuclides is carried out. The integrity of primary and secondary cement solidification is evaluated. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Hydrological Controls on Residual Contaminants Under Sustainable Remediation - 19287

This paper investigates the impact of natural aquifer's recharge shifts induced by precipitation changes on residual contaminants located in soil and groundwater, subject to sustainable remediation techniques. We illustrate five climate change scenarios which mimic shifts in the natural recharge regime. We evaluate the impact on different performance metrics that include contaminant concentrations at observation wells and contaminant export to a creek. The approach is demonstrated by simulating the tritium plume migration within a U.S. Department of Energy's nuclear reservations: the Savannah River Site F-Area. Results show that increasing the aquifers' recharge initially causes a decrease in the well concentrations due to dilution, and subsequently an increase due to the mobilization of contaminants from the vadose zone. As the recharge shift increases, the peak concentration is higher and may occur at an earlier stage. The mobilized contaminants reach the wells or control planes several years or decades later than the precipitation events thus monitoring near the source zone is important for early detecting mobilized contaminants. Moreover, we observe that, even when the well concentrations are significantly affected, the export at the control planes may not be affected by shifts in the natural recharge regime therefore the risk of downgradient population may be under control even under significant hydrological changes. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

SIT Makeup Effect on the Loss of Residual Heat Removal during Mid-loop Operation

For the loss of cooling during the mid-loop operation, the plant needs to have a sufficient time for operator action without active makeup measures such as a loss of alternating current (AC) power. This concern is raised after the Fukushima accident. Especially, in addition to the loss of residual heat removal (LORHR), if the AC power or active makeup measures are unavailable, the passive makeup using gravity feed or pressurized feed will provide sufficient time before core uncovery. This paper investigates means of the passive makeup measures using safety injection tank (SIT) after the LORHR event to prevent or delay the core uncovery and fuel failure for the typical advanced power reactor 1400 (APR1400). Unfortunately, the refueling water storage tank of APR1400 cannot be used for gravity makeup since it is located on the bottom of the containment with a lower elevation than the reactor vessel. So, the SIT makeup and the effect on the core uncovery are investigated. The results show that gravity makeup of a SIT provides insufficient means but the slightly pressurized SIT is required for sufficient operator action time for the LORHR with the station black out (SBO) during the mid-loop operation for the APR1400. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2015

The application of ALARP to legacy residues recovery processes on the Springfields site in the United Kingdom - 14333

In the United Kingdom, the legal framework for nuclear safety is established principally through the Health and Safety at Work Act 1974 (HSAW74) and the Nuclear Installations Act 1965 (NIA 65). Under HSAW74, employers are responsible for reducing risks, so far as is reasonably practicable, to their workers and others (including the public). This responsibility is elaborated further in relation to nuclear sites by NIA65, which establishes a nuclear site licensing regime whereby Nuclear Site Licenses are granted and subsequently regulated by the Office for Nuclear Regulation (ONR) within the Health and Safety Executive (HSE). In essence, ensuring that a risk has been reduced to 'As Low As Reasonably Practicable' (ALARP) is about weighing-up the risk against the sacrifice needed to reduce it. To avoid having to make this sacrifice, the Nuclear Site License holder (the Site Licensee) must be able to show that it would be grossly disproportionate to the benefits of risk reduction that would be achieved. Using 'reasonably practicable' allows the ONR to set goals for the Site Licensee, rather than being prescriptive. This flexibility can be a great advantage in that it allows the Site Licensee to consider a variety of options, and hence supports innovative approaches. However, it has drawbacks in that it requires both the Site Licensee and the regulators to exercise judgement; in reality, many decisions about risks and the measures that achieve ALARP are not straight-forward. Fortunately, various resources are available to the Site Licensee to aid these decisions. Three key facilities on the Westinghouse, Springfields Fuels Limited site at Preston in the UK (including the National Nuclear Laboratory's Preston Laboratory) undertake the clean-up of legacy residues from both fuel manufacturing operations on the site itself (dating back well over fifty years) and the wider nuclear industry. This paper discusses the key features of these three facilities to illustrate how ALARP considerations have shaped the operating regimes and associated criticality controls in those areas. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

Residual Dose Rates Analyses from Vent Lines Shield Block on the Target Cart at Spallation Neutron Source

The target carriage supports the mercury target vessel in the Spallation Neutron Source (SNS) in a cantilevered fashion and supplies the liquid mercury flowing to and from the target vessel. The target carriage is designed to move the target vessel into its target monolith position to receive the proton beam and then remove it horizontally back into an adjacent service cell, where the target vessel can be exchanged about 2-3 times per calendar year. At the time of the performed studies, the SNS mercury target can accept a proton beam at 1 GeV energy and 1.4 MW power; however, it will be upgraded to receive 1.3 GeV energy at 2 MW by the end of 2024 year [1]. The cart is practically a shield block on wheels to minimize fluxes and dose rates in the service cell downstream of the carriage. There are vent lines located inside a passage on top of the target carriage, and they are covered by a stepping-up steel shield block (vent lines shield block). Vent lines are permanently attached to the shield block. New vent lines with a different design are going to be installed. These lines are shielded by the new steel block to which the vent lines are attached. The estimate of the residual dose rates from the block after it is extracted from the target carriage is performed to estimate the radiation fields and to decide on the type of storage container to be used.

Popova, Irina I↗
DOE OSTI2024

Potential Integration Between Residual Biogenic Process Resources and Greener Hydrogen Production from Steam Reformers

Biomass conversion processes have varying efficiencies towards specific products like liquid fuels; process inefficiencies result in byproducts such as off-gases, heat, and solid residues such as char. The efficient use of these byproducts is key towards getting the maximum sustainability benefits from valuable biomass resources. For example, there are various utility product options that can utilize heat and off-gases from biomass pyrolysis processes; they include process heat and steam, hydrogen, fuel gas, and electricity. Further, there is potential for the use of the off-gases to supplement natural gas feed into steam reformers for hydrogen production. This presentation highlights results from previous analyses on tradeoffs based on utility byproduct choices (https://doi.org/10.1039/D3SE00745F); maximizing hydrogen production from off-gases is one potential winning strategy. This leads to the question regarding the utilization of these off-gases in existing steam reformers and the process impacts from feeding off-gases. Process modeling of a steam reformer system (https://doi.org/10.1002/adsu.20230021) quantifies those impacts and shows how much off-gas substitution is possible within the limits of an existing design with such an integration strategy.

biogenic gases↗
DOE OSTI2025

FLAW STABILITY ANALYSIS OF SURFACE CRACKS IN DOE STANDARD CANISTERS UNDER OPERATION LOADS AND WELDING RESIDUAL STRESSES

There are over 3000 commercial spent nuclear fuel (SNF) storage canisters that are made of stainless steel and planned for multi-purpose functions of SNF handling: interim storage, transportation, and ultimate disposal at a future SNF disposition location. To date, many multi-purpose canisters (MPC) are located in coastal regions for long-term storage. The canisters are fabricated by welding, and post-welding heat treatment is not required for relieving welding residual stresses (WRS). As a result, these canisters may be susceptible to chloride induced stress corrosion cracking (CISCC) due to the chloride-bearing marine salts. The flaw stability analysis of MPC canisters was performed at SRNL (i.e., PVP2016-4935 and PVP2016-63887) for through-wall flaws and for surface flaws respectively, where WRS was considered, and the failure assessment diagram (FAD)-based fracture mechanics method codified by API 579-1/ASME FFS-1-2007 Edition was adopted.

DOE standard canister↗
DOE OSTI2024

Air Classification of Forestry Residues for Fast Pyrolysis

Understanding critical biomass attributes through efficient fractionation is crucial for advancing sustainable pyrolysis for renewable energy and chemical production. This study investigates the intricate relationship between biomass preprocessing and pyrolysis product yields, employing the air classification technique for the treatment of loblolly pine residues with varying moisture content. A comprehensive exploration of the physicochemical properties of air-classified loblolly pine informs a sophisticated pyrolysis simulation model. Given the complex and multifaceted nature of biomass pyrolysis, operating across diverse temporal and spatial scales, a pyrolysis kinetics-based CFD–DEM simulation method is employed to predict product yields. Results showed that the elevated moisture content amplifies particle adhesiveness, necessitating augmented air velocities for effective separation, thereby influencing the efficiency of the separation process. While carbon and hydrogen contents exhibit relative stability across diverse moisture contents and blower frequencies, the oxygen content undergoes noticeable changes. For example, the oxygen contents were measured as 29.2 and 38.6 wt% in the light fraction of 30% moisture content sample at blower frequencies of 10 and 20 Hz, respectively. An intriguing finding emerges from pyrolysis simulation, indicating that a lower blower frequency in air classification moderately enhances bio-oil yield and significantly improves its quality, particularly in terms of water content. For instance, the water content in the bio-oil was about 1.5% and 10% in the heavy and light fractions, respectively from 10% moisture sample under 15 Hz blower frequency.

09 - BIOMASS FUELS↗
DOE OSTI2016

Experimental comparison of residual stresses for a thermomechanical model for the simulation of selective laser melting

Selective laser melting (SLM) is an additive manufacturing process in which multiple, successive layers of metal powders are heated via laser in order to build a part. Modeling of SLM requires consideration of the complex interaction between heat transfer and solid mechanics. Here, the present work describes the authors initial efforts to validate their first generation model. In particular, the comparison of model-generated solid mechanics results, including both deformation and stresses, is presented. Additionally, results of various perturbations of the process parameters and modeling strategies are discussed.

42 ENGINEERING↗