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Occupational dose reduction developments and data collected at nuclear power plants

Description: Occupational dose reduction developments and data collected at nuclear power plants have been described. Written descriptions of repetitive high dose jobs, their collective dose equivalent ranges and list of dose reduction techniques will aid in reducing collective dose equivalents from these dose-reduction targets. Knowing which components contribute to high maintenance or repair dose will aid in reducing routine maintenance collective dose equivalents. The radwaste dose reduction improvements will aid in reducing radwaste operations collective dose equivalent and reduce the number of radwaste workers who exceed their administrative dose limits. The identification and rating of managers' and workers' ALARA incentives will provide the basis for recommendations to improve dose reduction incentives. Lastly, the identification and rating of the key components of an ALARA program will aid in
Date: January 1, 1984
Creator: Dionne, B.J. & Baum, J.W.
Partner: UNT Libraries Government Documents Department

Criteria for safety-related operator actions

Description: The Safety-Related Operator Actions (SROA) Program was designed to provide information and data for use by NRC in assessing the performance of nuclear power plant (NPP) control room operators in responding to abnormal/emergency events. The primary effort involved collection and assessment of data from simulator training exercises and from historical records of abnormal/emergency events that have occurred in operating plants (field data). These data can be used to develop criteria for acceptability of the use of manual operator action for safety-related functions. Development of criteria for safety-related operator actions are considered.
Date: January 1, 1983
Creator: Gray, L.H. & Haas, P.M.
Partner: UNT Libraries Government Documents Department

Information-theoretic approach to uncertainty importance

Description: A method is presented for importance analysis in probabilistic risk assessments (PRA) for which the results of interest are characterized by full uncertainty distributions and not just point estimates. The method is based on information theory in which entropy is a measure of uncertainty of a probability density function. We define the relative uncertainty importance between two events as the ratio of the two exponents of the entropies. For the log-normal and log-uniform distributions the importance measure is comprised of the median (central tendency) and of the logarithm of the error factor (uncertainty). Thus, if accident sequences are ranked this way, and the error factors are not all equal, then a different rank order would result than if the sequences were ranked by the central tendency measure alone. As an illustration, the relative importance of internal events and in-plant fires was computed on the basis of existing PRA results.
Date: January 1, 1985
Creator: Park, C.K. & Bari, R.A.
Partner: UNT Libraries Government Documents Department

Testing and analysis of the Semiscale Mod-1 heater rod design

Description: The use of electrically heated nuclear fuel rod simulators in the Semiscale Program is traced from a historical viewpoint. The design of the Semiscale Mod-1 electrical heater rod and core simulator is discussed. Heater rod thermal response during transient thermal-hydraulic depressurization experiments conducted in the Mod-1 system, and analysis techniques and tests conducted to help quantify heater rod characteristics and behavior are presented.
Date: January 1, 1980
Creator: Larson, T.K.
Partner: UNT Libraries Government Documents Department

Application of software to development of reactor-safety codes

Description: Over the past two-and-a-half decades, the application of new techniques has reduced hardware cost for digital computer systems and increased computational speed by several orders of magnitude. A corresponding cost reduction in business and scientific software development has not occurred. The same situation is seen for software developed to model the thermohydraulic behavior of nuclear systems under hypothetical accident situations. For all cases this is particularly noted when costs over the total software life cycle are considered. A solution to this dilemma for reactor safety code systems has been demonstrated by applying the software engineering techniques which have been developed over the course of the last few years in the aerospace and business communities. These techniques have been applied recently with a great deal of success in four major projects at the Hanford Engineering Development Laboratory (HEDL): 1) a rewrite of a major safety code (MELT); 2) development of a new code system (CONACS) for description of the response of LMFBR containment to hypothetical accidents, and 3) development of two new modules for reactor safety analysis.
Date: September 1, 1980
Creator: Wilburn, N.P. & Niccoli, L.G.
Partner: UNT Libraries Government Documents Department

Application of software engineering to development of reactor-safety codes

Description: As a result of the drastically increasing cost of software and the lack of an engineering approach, the technology of Software Engineering is being developed. Software Engineering provides an answer to the increasing cost of developing and maintaining software. It has been applied extensively in the business and aerospace communities and is just now being applied to the development of scientific software and, in particular, to the development of reactor safety codes at HEDL.
Date: November 1, 1980
Creator: Wilburn, N P & Niccoli, L G
Partner: UNT Libraries Government Documents Department

Fission product decay heat studies of December 15, 1975

Description: The purpose of the project described is to study fission product decay heating rates, with emphasis on short decay times. Isothermal calorimetry is used to perform benchmark experiments for decay times between 20 seconds and 2000 seconds with an absolute accuracy of better than 5 percent. Experiments are being done with $sup 235$U and will be done eventually with $sup 239$Pu. Thermal neutron spectra are used for the irradiations. The project was initiated in July 1974. Final results for $sup 235$U are expected by 6-30-76, and for $sup 239$Pu by 1-1-77. Final reports for each task will follow the final data by 3 months. The work done to date is described together with the status of the final experimental configuration.
Date: February 26, 1976
Creator: Yarnell, J.L. & Bendt, P.J.
Partner: UNT Libraries Government Documents Department

Final report on PCRV thermal cylinder axial tendon failures

Description: The post-test examination of the failed tendons from the PCRV thermal cylinder experiment has been concluded. Failures in the wires are attributed to stress-corrosion cracking. The cause of tendon failures has not been unequivocably established, but they may have been due to nitrates in the duct. The wires employed in the manufacture of the tendons will crack in less than 72 hr in a 0.2 M solution of ammonium nitrate at 70$sup 0$C. The quality of the wires is poor, and surface cracks were detected. These could have acted as concentrating sites for both stress and the deleterious contaminants. It is believed that the factors that led to the failures in the thermal cylinder experiment were unique. An improper formulation of the epoxy resin did not provide the tendon anchor plate seal that was desired; indeed, the improper formulation is responsible for the high level of nitrogen in the ducts of the failed tendons. (auth)
Date: January 1, 1976
Creator: Canonico, D.A.; Griess, J.C. & Robinson, G.C.
Partner: UNT Libraries Government Documents Department

Technical specifications - enhancing the safety impact

Description: This report documents the work of an interoffice, interdisciplinary, NRC Task Group established in August 1983 to identify the scope and nature of problems with surveillance testing in current Technical Specifications and to develop alternative approaches that will provide better assurance that surveillance testing does not adversely impact safety. The Task Group concluded that some of the Technical Specifications have the potential for adversely affecting safety and some do not appear to be cost effective. The Task Group developed five recommendations for improvement. 15 references.
Date: November 1, 1983
Partner: UNT Libraries Government Documents Department

Licensee Event Report (LER) compilation for month of February 1984. Vol. 3, No. 2

Description: This monthly report contains LER operational information that was processed into the LER data file of the Nuclear Safety Information Center (NSIC) during this period. The LER summaries are arranged alphabetically by facility name and then chronologically by event date for each facility. Component, system, keyword, and component vendor indexes follow the summaries.
Date: March 1, 1984
Partner: UNT Libraries Government Documents Department

Underwater vapor phase burning of aluminum particles and on aluminum ignition during steam explosions

Description: Recently reported experimental studies on aluminum-water steam explosions indicate that there may be a critical metal temperature at which the process changes over from a physical explosion to one which is very violent and involves the rapid liberation of chemical energy. In this report we examine the hypothesis that vapor-phase burning of aluminum is a necessary condition for the occurrence of such ignition-type'' steam explosions. An available two-phase stagnation flow film-boiling model is used to calculate the steam flux to the vaporizing aluminum surface. Combining this calculation with the notion that there is an upper limit to the magnitude of the metal vaporization rate at which the reaction regime must change from vapor phase to surface burning, leads to prediction of the critical metal surface temperature below which vapor phase burning is impossible. The critical temperature is predicted for both the aluminum-water pre-mixture configuration in which coarse drops of aluminum are falling freely through water and for the finely-fragmented aluminum drops in the wake of the pressure shock that triggers'' the explosion. Vapor phase burning is predicted to be possible during the pre-mixture phase but not very likely during the trigger phase of a steam explosion. The implications of these findings in terms of the validity of the hypothesis that ignition may begin with the vapor phase burning of aluminum is discussed. Recently postulated, alternative mechanisms of underwater aluminum ignition are also discussed.
Date: September 1, 1991
Creator: Epstein, M. (Fauske and Associates, Inc., Burr Ridge, IL (United States))
Partner: UNT Libraries Government Documents Department

Top-down versus bottom-up processing of influence diagrams in probabilistic analysis

Description: Recent work by Phillips et al., and Selby et al., has shown that influence diagram methodology can be a useful analytical tool in reactor safety studies. An influence diagram is a graphical representation of probabilistic dependence within a system or event sequence. Bayesian statistics are employed to transform the relationships depicted in the influence diagram into the correct expression for a desired marginal probability (e.g. the top event). As with fault trees, top-down and bottom-up algorithms have emerged as the dominant methods for quantifying influence diagrams. Purpose of this paper is to demonstrate a potential error in employing the bottom-up algorithm when dealing with interdependencies. In addition, the computing efficiency of both methods is discussed.
Date: January 1, 1984
Creator: Timmerman, R.D.; Burns, T.J. & Dodds, H.L. Jr.
Partner: UNT Libraries Government Documents Department

Decision-theoretic methodology for reliability and risk allocation in nuclear power plants

Description: This paper describes a methodology for allocating reliability and risk to various reactor systems, subsystems, components, operations, and structures in a consistent manner, based on a set of global safety criteria which are not rigid. The problem is formulated as a multiattribute decision analysis paradigm; the multiobjective optimization, which is performed on a PRA model and reliability cost functions, serves as the guiding principle for reliability and risk allocation. The concept of noninferiority is used in the multiobjective optimization problem. Finding the noninferior solution set is the main theme of the current approach. The assessment of the decision maker's preferences could then be performed more easily on the noninferior solution set. Some results of the methodology applications to a nontrivial risk model are provided and several outstanding issues such as generic allocation and preference assessment are discussed.
Date: January 1, 1985
Creator: Cho, N.Z.; Papazoglou, I.A.; Bari, R.A. & El-Bassioni, A.
Partner: UNT Libraries Government Documents Department

Guidelines for earthquake ground motion definition for the eastern United States

Description: Guidelines for the determination of earthquake ground-motion definition for the eastern United States are established in this paper. Both far-field and near-field guidelines are given. The guidelines were based on an extensive review of the current procedures for specifying ground motion in the United States. Both empirical and theoretical procedures were used in establishing the guidelines because of the low seismicity in the eastern United States. Only a few large to great (M > 7.5) sized earthquakes have occurred in this region, no evidence of tectonic surface ruptures related to historic or Holocene earthquakes have been found, and no currently active plate boundaries of any kind are known in this region. Very little instrumented data has been gathered in the East. Theoretical procedures are proposed so that in regions of almost no data a reasonable level of seismic ground motion activity can be assumed. The guidelines are to be used to develop the Safe Shutdown Earthquake, SSE. A new procedure for establishing the Operating Basis Earthquake, OBE, is proposed, in particular for the eastern United States. The OBE would be developed using a probabilistic assessment of the geological conditions and the recurrence of seismic events at a site. These guidelines should be useful in development of seismic design requirements for future reactors. 17 refs., 2 figs., 1 tab.
Date: January 1, 1985
Creator: Gwaltney, R.C.; Aramayo, G.A. & Williams, R.T.
Partner: UNT Libraries Government Documents Department

Current algorithms used in reactor safety codes and the impact of future computer development on these algorithms

Description: Computational methods and solution procedures used in the US Nuclear Regulatory Commission's reactor safety systems codes, Transient Reactor Analysis Code (TRAC) and Reactor Leak and Power Safety Excursion Code (RELAP), are reviewed. Methods used in TRAC-PF1/MOD1, including the stability-enhancing two-step (SETS) technique, which permits fast computations by allowing time steps larger than the material Courant stability limit, are described in detail, and the differences from RELAP5/MOD2 are noted. Developments in computing, including parallel and vector processing, and their applicability to nuclear reactor safety codes are described. These developments, coupled with appropriate numerical methods, make detailed faster-than-real-time reactor safety analysis a realistic near-term possibility.
Date: January 1, 1985
Creator: Mahaffy, J.H.; Liles, D.R. & Woodruff, S.B.
Partner: UNT Libraries Government Documents Department

Heat transfer from bubbling pools. Progress report, July 1, 1975--October 1, 1975

Description: It is shown that the heat transfer characteristics of volume-heated boiling pools can be successfully modeled by non-boiling pools with internal gas injection. The strong influence of spatial distribution of bubble sites is relevant to estimates of boiling fuel attack on gas-releasing sacrificial materials. (auth)
Date: January 1, 1975
Creator: Bankoff, S G & Luk, A
Partner: UNT Libraries Government Documents Department

Allcuts: a fast, comprehensive fault tree analysis code

Description: A description, user instructions, and a source program listing are presented for ALLCUTS, a Fortran computer code for fault tree analysis. The code was specifically designed to be easy to use as well as fast, versatile, and powerful. It may easily be modified by a moderately skilled programer to fit the variable needs of the user and the capabilities of his computer. A code, BRANCH, for determining input data gate and bottom event interrelationships is also presented. (7 references) (auth)
Date: July 1, 1975
Creator: Van Slyke, W.J. & Griffing, D.E.
Partner: UNT Libraries Government Documents Department

Effects of water in film boiling over liquid metal melts

Description: Liquid-liquid boiling experiments have been performed with H/sub 2/O and liquid metal melts in the 100-series test matrix (Runs 121, 126, 127) and the VE test matrix. Some of the pre-explosion unstable film boiling data as well as observations from the explosive series have been previously reported.
Date: January 1, 1986
Creator: Greene, G.A.; Finfrock, C. & Burson, S.B.
Partner: UNT Libraries Government Documents Department