Risk assessment method for nuclear fuel cycle operations

A method is described for the identification and preliminary evaluation of potential accidents (release sequences) which could lead to the release of radioactive material from nuclear fuel cycle operations. Potential accident sequences are evaluated on the basis of risk. The basic elements of this method are presented along with its application to a conceptual high-level radioactive waste management

Ice-condenser aerosol tests

This report presents the results of an experimental investigation of aerosol particle transport and capture using a full-scale height and reduced-scale cross section test facility based on the design of the ice compartment of a pressurized water reactor (PWR) ice-condenser containment system. Results of 38 tests included thermal-hydraulic as well as aerosol particle data. Particle retention in the test section was greatly influenced by thermal-hydraulic and aerosol test parameters. Test-average decontamination factor (DF) ranged between 1.0 and 36 (retentions between {approximately}0 and 97.2%). The measured test-average particle retentions for tests without and with ice and steam ranged between DF = 1.0 and 2.2 and DF = 2.4 and 36, respectively. In order to apparent importance, parameters that caused particle retention in the test section in the presence of ice were steam mole fraction (SMF), noncondensible gas flow rate (residence time), particle solubility, and inlet particle size. Ice-basket section noncondensible flows greater than 0.1 m{sup 3}/s resulted in stable thermal stratification whereas flows less than 0.1 m{sup 3}/s resulted in thermal behavior termed meandering with frequent temperature crossovers between flow channels. 10 refs., 66 figs., 16 tabs

Preliminary Aging Assessment of Nuclear Air-Treatment and Cooling System Fans Preliminary Aging Assessment of Nuclear Air-Treatment and Cooling System Fans

Abstract A preliminary aging assessment of the fans used in nuclear air treatment and cooling systems was performed by the Pacific Northwest Laboratory as part of the U.S. Nuclear Regulatory Commission's Nuclear Plant Aging Research Program. Details from guides and standards for the design, testing, and installation of fans; results of failure surveys; and information concerning stressors, related aging mechanisms, and inspection, surveillance, and monitoring methods (ISMM) were compiled. Failure surveys suggest that about half of the failures reported for fans are primarily associated with aging. Aging mechanisms associated with the various fan components and resulting from mechanical, thermal, and environmental stressors include wear, fatigue, corrosion, and erosion of metals and the deterioration of belts and lubricants. A bearing is the component most frequently linked to fan failure. The assessment also suggests that ISMM that will detect irregularities arising from improper lubrication, cooling, alignment, and balance of the various components should aid in counteracting many of the aging effects that could impair fan performance. An expanded program, to define and evaluate the adequacy of current ISMM and maintenance practices and to include a documented Phase I aging assessment, is recommended. iii Summary This report presents a preliminary aging assessment of the fans used in nuclear air treatment and cooling systems. The work was performed by the Pacific Northwest Laboratory as part of the U.S. Nuclear Regulatory Commission's Nuclear Plant Aging Research Program. Details from guides and standards for the design, testing, and installation of fans; results of failure surveys; and information concerning stressors, related aging mechanisms, and inspection, surveillance, and monitoring methods (ISMM) are included in the report. Fans are used to recirculate, supply, andlor exhaust large quantities of air in several nuclear power plant air-treatment (cleaning) and air-cooling systems. Failure of these systems can impact both plant and public safety. Fans are used to direct air containing radioactive contaminants through the filters and adorbers that can be the last barrier to the release of radioactivity to the public following an accident. Furthermore, fans are components of systems needed to ensure the safe shutdown of the plant or allow equipment to be serviced. Satisfactory performance of certain airtreatment systems is essential to ensure control room habitability. Fans are also components of air-treatment and cooling systems that provide a safe environment for personnel and a controlled environment for equipment during normal operations. The results of the preliminary aging assessment of fans suggest that aging degradation is important when considering fan failure. The Code on Nuclear Air and Gas Treatment addresses the consideration of aging as part of fan design. Failure surveys containing information on aging and wear effects imply that about half of the failures reported for fans are primarily associated with aging. Aging mechanisms associated with the various fan components and resulting from mechanical, thermal, and environmental stressors include wear, fatigue, corrosion, and erosion of metals; and the deterioration and degradation of belts and lubricants. A bearing is the component most frequently linked to fan failure. The assessment also suggests that ISMM that will detect irregularities arising from improper lubrication, cooling, alignment, and balance of the various components should aid in counteracting many of the aging effects that could impair fan performance. The observation that aging degradation appears to be an important factor in fan failure, reinforced by the fact that failure can impact both plant and public safety, suggests the need for further study. The results of an expanded investigation, an effort that would focus on identifying and evaluating current ISMM and maintenance practices, would ultimately be combined with those of this preliminary study in the form of a published Phase I interim aging assessment

UC (Series) 25, Metals, Ceramics, and Materials

Report that summarizes out-of-reactor tests undertaken to determine operating conditions, estimate damage from and extent of fretting corrosion, and describe continuing tests planned to monitor and eliminate this corrosion

Preliminary Aging Assessment of Nuclear Air-Treatment and Cooling System Fans

A preliminary aging assessment of the fans used in nuclear air treatment and cooling systems was performed by the Pacific Northwest Laboratory as part of the U.S. Nuclear Regulatory Commission's Nuclear Plant Aging Research Program. Details from guides and standards for the design, testing, and installation of fans; results of failure surveys; and information concerning stressors, related aging mechanisms, and inspection, surveillance, and monitoring methods (ISMM) were compiled. Failure surveys suggest that about half of the failures reported for fans are primarily associated with aging. Aging mechanisms associated with the various fan components and resulting from mechanical, thermal, and environmental stressors include wear, fatigue, corrosion, and erosion of metals and the deterioration of belts and lubricants. A bearing is the component most frequently linked to fan failure. The assessment also suggests that ISMM that will detect irregularities arising from improper lubrication, cooling, alignment, and balance of the various components should aid in counteracting many of the aging effects that could impair fan performance. An expanded program, to define and evaluate the adequacy of current ISMM and maintenance practices and to include a documented Phase I aging assessment, is recommended

CLIRA DECAY HEAT REMOVAL TEST.

This report describes the design and fabrication of an electrically heated test section that was used to simulate the heat transport associated with the handling, after irradiation and discharge from the reactor vessel, of a fueled Fast Flux Test Facility (FFTF) closed loop test assembly while in the air-cooled ex-vessel handling machine

Atomic Energy Commission Reports

Report discussing the Plutonium Recycle Critical Facility (PRCF). The reactor, building, associated equipment, operating program, safety, and operating procedures are described

Safety assessment of geologic repositories for nuclear waste

Consideration of geologic isolation for final disposition of radioactive wastes has led to the need for evaluation of the safety of the concept. Such evaluations require consideration of factors not encountered in conventional risk analysis: consequences at times and places far removed from the repository site; indirect, complex, and alternative pathways between the waste and the point of potential consequences; a highly limited data base; and limited opportunity for experimental verification of results. R and D programs to provide technical safety evaluations are under way. Three methods are being considered for the probabilistic aspects of the evaluations: fault tree analysis, repository simulation analysis, and system stability analysis. Nuclide transport models, currently in a relatively advanced state of development, are used to evaluate consequences of postulated loss of geologic isolation. This paper outlines the safety assessment methods, unique features of the assessment problem that affect selection of methods and reliability of results, and available results. It also discusses potential directions for future work