skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: PROBABILISTIC ASSESSMENT OF A CRITICALITY IN A WASTE CONTAINER AT SRS

Abstract

Transuranic solid waste that has been generated as a result of the production of nuclear material for the United States defense program at the Savannah River Site (SRS) has been stored in more than 30,000 55-gallon drums and various size carbon steel boxes since 1953. Nearly two thirds of those containers have been processed and shipped to the Waste Isolation Pilot Plant. Among the containers assayed so far, the results indicate several drums with fissile inventories significantly higher (600-1000 grams {sup 239}Pu) than their original assigned values. While part of this discrepancy can be attributed to the past limited assay capabilities, human errors are believed to be the primary contributor. This paper summarizes an assessment of the probability of occurrence of a criticality accident during handling of the remaining transuranic waste containers at SRS.

Authors:
Publication Date:
Research Org.:
SRS
Sponsoring Org.:
USDOE
OSTI Identifier:
897091
Report Number(s):
WSRC-STI-2006-00378
TRN: US0700913
DOE Contract Number:
DE-AC09-96SR18500
Resource Type:
Conference
Resource Relation:
Conference: ANS 2007 Annual Meeting
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; 36 MATERIALS SCIENCE; CARBON STEELS; CONTAINERS; CRITICALITY; INVENTORIES; PROBABILITY; PRODUCTION; RADIATION ACCIDENTS; SAVANNAH RIVER PLANT; SOLID WASTES; WASTES; WIPP

Citation Formats

Eghbali, D. PROBABILISTIC ASSESSMENT OF A CRITICALITY IN A WASTE CONTAINER AT SRS. United States: N. p., 2006. Web.
Eghbali, D. PROBABILISTIC ASSESSMENT OF A CRITICALITY IN A WASTE CONTAINER AT SRS. United States.
Eghbali, D. Tue . "PROBABILISTIC ASSESSMENT OF A CRITICALITY IN A WASTE CONTAINER AT SRS". United States. doi:. https://www.osti.gov/servlets/purl/897091.
@article{osti_897091,
title = {PROBABILISTIC ASSESSMENT OF A CRITICALITY IN A WASTE CONTAINER AT SRS},
author = {Eghbali, D},
abstractNote = {Transuranic solid waste that has been generated as a result of the production of nuclear material for the United States defense program at the Savannah River Site (SRS) has been stored in more than 30,000 55-gallon drums and various size carbon steel boxes since 1953. Nearly two thirds of those containers have been processed and shipped to the Waste Isolation Pilot Plant. Among the containers assayed so far, the results indicate several drums with fissile inventories significantly higher (600-1000 grams {sup 239}Pu) than their original assigned values. While part of this discrepancy can be attributed to the past limited assay capabilities, human errors are believed to be the primary contributor. This paper summarizes an assessment of the probability of occurrence of a criticality accident during handling of the remaining transuranic waste containers at SRS.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Dec 26 00:00:00 EST 2006},
month = {Tue Dec 26 00:00:00 EST 2006}
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share:
  • This analysis is prepared by the Mined Geologic Disposal System (MGDS) Waste Package Development Department (WPDD) to provide an assessment of the present waste package design from a criticality risk standpoint. The specific objectives of this initial analysis are to: (1) Establish a process for determining the probability of waste package criticality as a function of time (in terms of a cumulative distribution function, probability distribution function, or expected number of criticalities in a specified time interval) for various waste package concepts; (2) Demonstrate the established process by estimating the probability of criticality as a function of time since emplacementmore » for an intact multi-purpose canister waste package (MPC-WP) configuration; (3) Identify the dominant sequences leading to waste package criticality for subsequent detailed analysis. The purpose of this analysis is to document and demonstrate the developed process as it has been applied to the MPC-WP. This revision is performed to correct deficiencies in the previous revision and provide further detail on the calculations performed. This analysis is similar to that performed for the uncanistered fuel waste package (UCF-WP, B00000000-01717-2200-00079).« less
  • Use of gadolinium as a neutron poison has been proposed for disposing of several metric tons of excess plutonium at the Savannah River Site (SRS). The plutonium will first be dissolved in nitric acid in small batches. Gadolinium nitrate will then be added to the plutonium nitrate solution. The Gd-poisoned plutonium solution will be neutralized and transferred to large under-ground tanks. The pH of small batches of neutralized plutonium solution will be adjusted prior to addition of the glass frit for eventual production as glass logs. The use of gadolinium as the neutron poison would minimize the number of glassmore » logs generated from this disposition. The primary criticality safety concerns regarding the disposal process are: (1) maintaining neutron moderation under all processing conditions since gadolinium has a very large absorption cross section for thermal neutrons, (2) characteristics of plutonium and gadolinium precipitation during the neutralization process, (3) mixing characteristics of the precipitate to ensure that plutonium would remain homogeneously mixed with gadolinium, and (4) potential separation of plutonium and gadolinium during nitric and formic acids addition. A number of experiments were conducted at the Savannah River National Laboratory to study the behavior of plutonium and gadolinium at various stages of the disposition process.« less
  • Since 1973 the Savannah River Laboratory (SRL) has used Probabilistic Risk Assessment to determine the frequency for criticality accidents at the Savannah River Site. The Savannah River Site is unique in that it has a detailed, site specific, data bank based on 35 years of facility operation. Use of this data bank with Probabilistic Risk Assessment precipitated facility actions which resulted in the reduction of the calculated criticality frequency by as much as two orders of magnitude. Probabilistic Risk Assessment has also been used to quantify the impact of non-process-related systems on criticality safety.
  • The storage of high-level spent reactor fuel in a proposed national geologic repository will require the construction of containers to be placed in boreholes drilled into the host rock. Federal regulations require that the fuel be maintained subcritical under normal or accident conditions. This is determined through the calculation of a neutron multiplication factor, k{sub eff}, that must remain below 0.95. Criticality will play an important role in the container design, the internal configuration of the fuel, and the selection of neutron poisons. An analysis of k{sub eff} should be a normal step in the conceptualization of new waste containermore » designs. Unlike thermal effects in a proposed repository, criticality will remain a problem long after the 10,000 year lifetime of the facility. In this study, nuclear criticality has been determined for the proposed spent fuel container in various situations that include varying fuel enrichment and partial air gap flooding. Results will be presented to demonstrate the impact of these variables on the design of a safe spent fuel container.« less
  • Alloy 22 (UNS N06022) is the candidate material for the corrosion barrier of the double-wall waste package (WP) for the disposal of high-Gel nuclear waste at the proposed Yucca Mountain repository. A probabilistic temperature-dependent general corrosion model for the WP outer barrier (WPOB) was developed based on the 5-year weight-loss measurements of Alloy 22 crevice samples. The 5-year corrosion rate distribution is represented by a Weibull distribution, with scale factors = 8.88, shape factor b = 1.62, and location factor l = 0. The temperature-dependence of the general corrosion rate was modeled using an Arrhenius relation. An activation energy ofmore » 25.91 {+-} 2.46 kJ/mol was determined from the corrosion rates obtained from the short-term polarization resistance data for Alloy 22 specimens tested for a wide range of sample configurations, metallurgical conditions, and exposure conditions (temperature and water chemistry). Analysis of the data from the current study and the literature indicates that the activation energies of general corrosion rate of highly corrosion resistant Ni-Cr-Mo alloys including Alloy 22 are similar and do not change significantly, as the general corrosion rate decreases with the exposure time. The 5-year corrosion rates were conservatively selected for extrapolation over the repository time scale. Because of very low general corrosion rates of the WPOB for the conditions expected in the proposed repository, the WP performance will not be limited by general corrosion for the repository regulatory time period. The current conservative approach for the constant (time-independent) general corrosion rate at a given temperature provides an additional confidence for the general corrosion model.« less