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Environmental radiation safety: plutonium/soil interactions for plutonium particles in soil

Description: The goal of this project is to provide information useful in estimating hazards related to resuspension characteristics and subsequent aerodynamic behavior of aerosols from a mixing of soil and /sup 238/PuO/sub 2/. Experiments were carried out to determine whether simple models, used to predict the total activity concentration of resuspended particles, need to be modified to account for changes in the /sup 238/PuO/sub 2/ activity distribution on resuspended particles due to aging of the soil mixture under humid or dry conditions. A literature search revealed that one model, based on the suspension factors, S/sub f/, may be a useful predictor of hazard reduction irrespective of site. Our experiments demonstrated little or no change in the activity of resuspended particles following humid or dry aging of the soil-/sup 238/PuO/sub 2/ mixture. Additional terms for activity distribution changes should not be needed for the simple resuspension hazard model.
Date: December 1, 1980
Creator: Moss, O.R.; Rossingnol, E.J.; Cannon, W.C. & Stevens, D.L.
Partner: UNT Libraries Government Documents Department

VISA: a computer code for predicting the probability of reactor pressure-vessel failure. [PWR]

Description: The VISA (Vessel Integrity Simulation Analysis) code was developed as part of the NRC staff evaluation of pressurized thermal shock. VISA uses Monte Carlo simulation to evaluate the failure probability of a pressurized water reactor (PWR) pressure vessel subjected to a pressure and thermal transient specified by the user. Linear elastic fracture mechanics are used to model crack initiation and propagation. parameters for initial crack size, copper content, initial RT/sub NDT/, fluence, crack-initiation fracture toughness, and arrest fracture toughness are treated as random variables. This report documents the version of VISA used in the NRC staff report (Policy Issue from J.W. Dircks to NRC Commissioners, Enclosure A: NRC Staff Evaluation of Pressurized Thermal Shock, November 1982, SECY-82-465) and includes a user's guide for the code.
Date: September 1, 1983
Creator: Stevens, D.L.; Simonen, F.A.; Strosnider, J. Jr.; Klecker, R.W.; Engel, D.W. & Johnson, K.I.
Partner: UNT Libraries Government Documents Department

Risk-based fault tree analysis method for identification, preliminary evaluation, and screening of potential accidental release sequences in nuclear fuel cycle operations

Description: A method is described for identification, preliminary evaluation, and screening of potential accident sequences leading to uncontrolled release of radioactive materials. Included is a procedure for estimating the risk sum of all identified sequences. In addition, portions of the procedures have been developed for detailed analysis of the dominant (highest risk) sequences so screened. This method was developed for the ERDA-sponsored risk analysis of systems for managing high-level waste, part of the Waste Fixation Program (WFP). The method begins with certain preliminary analyses. The facility and operation are described and analysis bounds are established. A type of fault tree construction, the ''to/through'' approach, was chosen for the WFP waste management system. The to/through fault tree approach offers advantages over others in several respects. The analysis is considered more complete because the system is treated as a whole. The screening process was successfully demonstrated on a conceptual waste management system for the Waste Fixation Program. Fault trees were constructed and evaluated for processing, handling, transporting, and storing high-level waste. Trees of up to 14,000,000 release sequences (BICS-Boolean-indicated cut sets) were screened and the top few hundred or thousand sequences preliminarily ranked. An estimate of the total risk represented in the fault tree was also obtained. (auth)
Date: January 1, 1976
Creator: Smith, T. H.; Pelto, P. J.; Stevens, D. L.; Seybold, G. D.; Purcell, W. L. & Kimmel, L. V.
Partner: UNT Libraries Government Documents Department

Mathematical model for predicting the probability of acute mortality in a human population exposed to accidentally released airborne radionuclides. Final report for Phase I

Description: A mathematical model was constructed for the purpose of predicting the fraction of human population which would die within 1 year of an accidental exposure to airborne radionuclides. The model is based on data from laboratory experiments with rats, dogs and baboons, and from human epidemiological data. Doses from external, whole-body irradiation and from inhaled, alpha- and beta-emitting radionuclides are calculated for several organs. The probabilities of death from radiation pneumonitis and from bone marrow irradiation are predicted from doses accumulated within 30 days of exposure to the radioactive aerosol. The model is compared with existing similar models under hypothetical exposure conditions. Suggestions for further experiments with inhaled radionuclides are included. 25 refs., 16 figs., 13 tabs.
Date: May 1, 1980
Creator: Filipy, R.E.; Borst, F.J.; Cross, F.T.; Park, J.F.; Moss, O.R.; Roswell, R.L. et al.
Partner: UNT Libraries Government Documents Department

PNL Technical Review of Pressurized Thermal Shock Issues Supplement 1: Technical Critique of the NRC Near-Term Screening Criteria

Description: Pacific Northwest Laboratory (PNL) provided a technical critique of the draft report, NRC Staff Evaluation of Pressurized Thermal Shock, dated September 13, 1982. This report provided the basis for the NRC near-term regulatory position on pressurized thermal shock {PTS) and recommended a generic screening criteria for welds in the vessel beltline region. The PNL staff concluded that the screening criteria were adequate to meet the intent of the NRC safety goal and to retain past predictions of vessel reliability. The conclusion was based on selecting the plant-specific nilductility transition reference temperature (RT{sub NDT}) in the conservative manner described within the staff report. Conservative and unconservative factors were mentioned throughout the NRC staff report. The PNL staff has listed these factors together with unknown (may be either conservative or unconservative) factors and estimated, where possible, the range in °F RT{sub NDT}. The unknown factors were so widespread that the PNL staff recommended that specific conservatisms not be reduced until the unknowns are further resolved.
Date: May 1, 1983
Creator: Pederson, L. T.; Apley, W. J.; Bian, S. H.; Pelto, P. J.; Simonen, E. P.; Simonen, F. A. et al.
Partner: UNT Libraries Government Documents Department

PNL technical review of pressurized thermal-shock issues. [PWR]

Description: Pacific Northwest Laboratory (PNL) was asked to develop and recommend a regulatory position that the Nuclear Regulatory Commission (NRC) should adopt regarding the ability of reactor pressure vessels to withstand the effects of pressurized thermal shock (PTS). Licensees of eight pressurized water reactors provided NRC with estimates of remaining effective full power years before corrective actions would be required to prevent an unsafe operating condition. PNL reviewed these responses and the results of supporting research and concluded that none of the eight reactors would undergo vessel failure from a PTS event before several more years of operation. Operator actions, however, were often required to terminate a PTS event before it deteriorated to the point where failure could occur. Therefore, the near-term (less than one year) recommendation is to upgrade, on a site-specific basis, operational procedures, training, and control room instrumentation. Also, uniform criteria should be developed by NRC for use during future licensee analyses. Finally, it was recommended that NRC upgrade nondestructive inspection techniques used during vessel examinations and become more involved in the evaluation of annealing requirements.
Date: July 1, 1982
Creator: Pedersen, L.T.; Apley, W.J.; Bian, S.H.; Defferding, L.J.; Morgenstern, M.H.; Pelto, P.J. et al.
Partner: UNT Libraries Government Documents Department