[en] This report provides an evaluation of Hanford tank bump accident potential and consequences during waste retrieval operations. The purpose of this report is to consider the best available new information to support recommendations for safety controls. A new tank bump accident analysis for safe storage (Epstein et al. 2000) is extended for this purpose. A tank bump is a postulated event in which gases, consisting mostly of water vapor, are suddenly emitted from the waste and cause tank headspace pressurization. Tank bump scenarios, physical models, and frequency and consequence methods are fully described in Epstein et al. (2000). The analysis scope is waste retrieval from double-shell tanks (DSTs) including operation of equipment such as mixer pumps and air lift circulators. The analysis considers physical mechanisms for tank bump to formulate criteria for bump potential during retrieval, application of the criteria to the DSTs, evaluation of bump frequency, and consequence analysis of a bump. The result of the consequence analysis is the mass of waste released from tanks; radiological dose is calculated using standard methods (Cowley et al. 2000)

[en] This report provides a new evaluation of the Hanford tank bump accident analysis and consequences for incorporation into the Authorization Basis. The analysis scope is for the safe storage of waste in its current configuration in single-shell and double-shell tanks

[en] This report documents the results of the second phase of parameter quantification by the flammable gas expert panel. This second phase is focused on the analysis of flammable gas accidents in the Hanford Site double-shell tanks. The first phase of parameter quantification, performed in 1997 was focused on the analysis of Hanford single-shell tanks

[en] The purpose of this report is to document all software verification and validation activities, results, and findings related to the development of Resolve Version 2.5 for the analysis of flammable gas accidents in Hanford Site waste tanks

[en] Following a 1990 investigation into flammable gas generation, retention, and release mechanisms within the Hanford Site high-level waste tanks, personnel concluded that the existing Authorization Basis documentation did not adequately evaluate flammable gas hazards. This declaration was based primarily on the fact that personnel did not adequately consider hydrogen and nitrous oxide evolution within the material in certain waste tanks and subsequent hypothetical ignition in the development of safety documentation for the waste tanks. The US Department of Energy-Headquarters subsequently declared an Unreviewed Safety Question (USQ). Although work scope has been focused on closure of the USQ since 1990, the DOE has yet to close the USQ because of considerable uncertainty regarding essential technical parameters and associated risk. The DOE recently approved a Basis for Interim Operation to revise the Authorization Basis for managing the tank farms, however, the USQ remains open. The two fundamental requirements for closure of the flammable gas USQ are as follows: development of a defensible technical basis for existing controls; development of a process to assess the adequacy of controls as the waste tank mission progresses

[en] Following a 1990 investigation into flammable gas generation, retention, and release mechanisms within the Hanford Site high-level waste tanks, personnel concluded that the existing Authorization Basis documentation did not adequately evaluate flammable gas hazards. The US Department of Energy Headquarters subsequently declared the flammable gas hazard as an unresolved safety issue. Although work scope has been focused on resolution of the issue, it has yet to be resolved due to considerable uncertainty regarding essential technical parameters and associated risk. Resolution of the Flammable Gas Safety Issue will include the identification of a set of controls for the Authorization Basis for the tanks which will require a safety analysis of flammable gas accidents. A traditional nuclear facility safety analysis is based primarily on the analysis of a set of bounding accidents to represent the risks of the possible accidents and hazardous conditions at a facility. While this approach may provide some indication of the bounding consequences of accidents for facilities, it does not provide a satisfactory basis for identification of facility risk or safety controls when there is considerable uncertainty associated with accident phenomena and/or data as is the case with potential flammable gas accidents at the Hanford Site. This is due to the difficulties in identifying the bounding case and reaching consensus among safety analysts, facility operations and engineering, and the regulator on the implications of the safety analysis results. In addition, the bounding cases are frequently based on simplifying assumptions that make the analysis results insensitive to variations among facilities or the impact of alternative safety control strategies. The existing safety analysis of flammable gas accidents for the Tank Waste Remediation system (TWRS) at the Hanford Site has these difficulties. However, Hanford Site personnel are developing a refined safety analysis approach which will solve the two basic difficulties of defining the bounding case and assessing the impact of controls. The refined safety analysis does this by explicitly quantifying the effects of the uncertainty in the state of knowledge about accident phenomena and data and providing a consistent basis for calculating the impact of alternative control strategies on parameters that affect accident risk. The refined analysis allows the assessment of the risk impact of the variability in conditions (e.g., waste inventory) among storage tanks in the TWRS. Finally, the refined flammable gas accident safety analysis supports sensitivity studies to examine the impact on the results of differences in flammable gas accident perspectives

[en] This document is a compilation of presentation packages and white papers for the Flammable Gas Double Shell Tank Expert Elicitation Workshop number-sign 2. For each presentation given by the different authors, a separate section was developed. The purpose for issuing these workshop presentation packages and white papers as a supporting document is to provide traceability and a Quality Assurance record for future reference to these packages

[en] Significant changes have been made to all of the original vapor characterization reports. This report documents specific headspace gas and vapor characterization results for all vapor sampling events to date. In addition, changes have been made to the original vapor reports to qualify the data based on quality assurance issues associated with the performing laboratories

[en] The technical basis for the nuclear criticality safety of stored wastes at the Hanford Site Tank Farm Complex was reviewed by a team of senior technical personnel whose expertise covered all appropriate aspects of fissile materials chemistry and physics. The team concluded that the detailed and documented nucleonics-related studies underlying the waste tanks criticality safety basis were sound. The team concluded that, under current plutonium inventories and operating conditions, a nuclear criticality accident is incredible in any of the Hanford single-shell tanks (SST), double-shell tanks (DST), or double-contained receiver tanks (DCRTS) on the Hanford Site

[en] High-level radioactive waste has been stored in large cylindrical underground tanks at the US Department of Energy's (DOE's) Hanford Site in southeastern Washington State since 1944. Approximately 285 million liters of caustic waste are contained in 177 carbon-steel tanks. Radiolytic, thermolytic, and chemical reactions in the radioactive waste generate flammable gases such as hydrogen and ammonia. These gas mixtures also include an oxidizer (nitrous oxide) and an inert component (nitrogen). Some wastes retain the gas mixture until a large amount builds up, and then a short-term gas release occurs in the tank headspace. Such a gas release can result in a flammable concentration in the tank headspace. Following a 1990 investigation into flammable gas generation, retention, and release mechanisms within the Hanford Site high-level waste tanks, personnel concluded that the existing authorization basis documentation did not adequately evaluate flammable gas hazards. The existing authorization basis to establish effective controls for the flammable gas accident analysis is based on operational experience and qualitative judgment. Therefore, the flammable gas safety issue remains open because of considerable uncertainty regarding essential technical parameters and associated risk. The Project Hanford Management Contract team has formulated a refined safety analysis approach to resolve the flammable gas safety issue