ISSN:0029-5450    

DOI:10.13182/NT87-A34002

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

Application of computerized tomography (CT) in two-phase flows has been discussed in the existing literature. Development of a fast, but simple, algorithm for reconstructing the density p or the absorption coefficientμis attempted. The algorithm, involving radial polynomials (RAP), has been tested using simulated data for radially symmetric bubbly and annular two-phase flows. The RAP algorithm can also be applied in nonsymmetric flow situations, provided the information required is the cross-sectionally averaged density. The results indicate RAP to be a fast and accurate method for CT reconstructions involving an air-water flow system.

ISSN:0029-5450    

DOI:10.13182/NT87-A34003

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

The emergency core cooling systems (ECCSs) at a reactor site have a dual power source for their assured operation if and when needed. The normal power source is the off-site ac power. In the unlikely event of loss of all off-site power, emergency diesel generators (DGs) are the backup ac source. Thus, there is an incentive to ensure that the reliability of DGs at operating plants is maintained at an acceptable level. A potential contributor to observed diesel degradation is the fast start and loading interval (∼10 s) demanded of the emergency DGs. Such fast start intervals result from the performance required of the ECCS to meet the U.S. Nuclear Regulatory Commission (NRC) acceptance criteria for a hypothetical large-break loss-of-coolant accident (LOCA) (design basis accident) concurrent with a loss of off-site power. The guidelines established by the NRC for the ECCS performance evaluation, which are stated in Appendix K of 10CFR50, have several built-in arbitrary conservatisms. Recently, the NRC outlined in SECY-83-472 a new approach for performing ECCS analysis and has given approval to General Electric to use this new approach in their SAFER/GESTR LOCA analysis computer code. The sensitivity of peak cladding temperature (PCT) is determined using the new realistic LOCA analysis approach for various DG start durations. A quantitative assessment of the various diesel start durations using NRC licensing assumptions was made to determine the impact on the PCT. The results for a boiling water reactor (BWR/6) show that when using licensing assumptions and the SAFER/GESTR code, the PCT that is determined during a design basis LOCA for the present 10-s DG start criteria is∼593°C. This is far below the prescribed limit of 1204.4°C. The results also show that the PCT varies only a small amount with diesel start times of 10 to 30 s. Thus, the diesel start time for the class of reactors analyzed in this study could be changed from 10 to 30 s without the loss of any LOCA safety margin. The results further show that for an 871.1°C PCT, which is the current NRC-approved SAFER application PCT limit, the DG start time can be 70 s (compared to the present specified 10 s). The DG start time could be increased to 118 s when and if, in the future, the SAFER code is qualified to a PCT limit of 1204.4°C for licensing calculations. This work is of interest to nuclear utilities as a means of increasing operational flexibility and to help improve diesel reliability.

ISSN:0029-5450    

DOI:10.13182/NT87-A34004

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

Past experiences such as the Bhopal incident in India (1985) and the Chernobyl reactor accident in the USSR (April 1986) stress the significance of timely evacuations as a protective measure against accidental releases of radioactivity or toxic material to the atmosphere. While timely evacuation has the potential to save many lives, there is a finite risk associated with the act of evacuation itself. From a detailed questionnaire, data were obtained on 320 past evacuation events that took place in the United States from 1972 to 1985 to quantify risks associated with evacuations. Subsequently, these risks are used to assess the societal impact associated with evacuations of sectors of different radii surrounding a nuclear power plant. It is found that risks associated with evacuation of a 16-km radius to be∼100 times greater than the risks associated with a 3.2-km radius evacuation. Also, an individual’s fatality risk due to evacuation is found to be equal to the risk attributed to a radiation dose between 110 and 5800 mrem (0.0011 and 0.058 Gy), depending on the dose response model used to assess the radiation risk for a 320-km round-trip evacuation. This concept can be applied to nonnuclear incidents such as rail accidents and other industrial or natural incidents.

ISSN:0029-5450    

DOI:10.13182/NT87-A34005

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

The description of containment iodine behavior in reactor accident sequences involves a combination of iodine volatility effects, deposition/revaporization processes, and mass transport of iodine species. The formation and retention of volatile organic iodides such as methyl iodide, CH3I, are important factors in determining iodine source terms. Tests have shown that the formation of organic iodide was enhanced by radiation and iodine in the chemical form of I2. Methyl iodide, the only organic iodide detected in measurable quantities, formed predominantly in aqueous solution even when the organic material was introduced to the gas phase.

ISSN:0029-5450    

DOI:10.13182/NT87-A34006

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

A statistical decision theory provides a rational theoretical model that enables an algorithm to select appropriate off-site protective actions. Existing knowledge on safety system and containment event trees, the spectrum of release states, and statistical decision theory were used to develop a model that accommodates actual and potential radiation risks and nonradiological risks such as risks of evacuation in selecting off-site protective actions. The usefulness of the model developed is illustrated by applying it to the Three Mile Island Unit 2 (TMI-2) scenario and comparing the actual decisions made with the decisions provided by the model. Conclusions drawn by modeling the TMI-2 related data are in general agreement with off-site protective actions taken. Finally, the model is used to illustrate the extremely low likelihood of the occurrence of accident scenarios that require evacuations beyond a 3.2-km radius and to support a plume exposure pathway emergency planning zone of 3.2 to 8 km for reduced source terms.

ISSN:0029-5450    

DOI:10.13182/NT87-A34007

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractOne of the elements used to compute the dryout heat flux of a debris bed is the capillary pressure/saturation curve. This relationship describes the pressure difference between liquid and vapor phases in a porous bed as a function of saturation. It is used in the calculation of the liquid and vapor pressure drops in the debris and in the calculation of channel depth. The first complete correlation of capillary pressure/saturation data was reported in 1941 by Leverett. Leverett demonstrated that the data for unconsolidated sand in the 45- to 180-µm range could be non-dimensionalized using the liquid surface tension, bed permeability, and void fraction. At the time, the primary interest was in geologic materials and further work on unconsolidated particulate was limited. The presented measurements of capillary pressure are designed to check the range of validity of the Leverett correlation. For beds with narrow particle size distributions, the Leverett correlation is found to be adequate. For beds composed of broad size distributions, the capillary pressure curve changed significantly.

ISSN:0029-5450    

DOI:10.13182/NT87-A34008

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

Weakly acidic carboxylic resin, with no sulfur atoms, was selected as an alternative to sulfonic cation exchange resin for water treatment in nuclear power plants. Pyrolysis experiments showed that no corrosive SOx gas was produced by the former, and its residual ratio was one-third that of the latter conventional resin. Spent resin treatment then becomes relatively simple for the new resin. Subsequently, filtration characteristics were examined by use of simulated condensate water, assuming that the resin was applied to a filter demineralizer. The resin lifetime was∼1.5 times that of the conventional one, suggesting that the amount of spent resin generated from a filter demineralizer could be reduced to about two-thirds. Therefore, the carboxylic resin showed favorable features for both water purification and spent resin treatment.

ISSN:0029-5450    

DOI:10.13182/NT87-A34009

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

Direct dissolution of uranium carbide was found to be very effective when it was refluxed with an 18 M H2SO4-15 M HNO3(1:1) mixture. Clear solutions could be obtained within 1 h. Uranium-plutonium carbide, as well as PuO2could also be dissolved in 1 to 2 h in the same way. Other nuclear materials, UO2+ C and UO2+ PuO2+ C, needed longer duration for complete dissolution. When the proportion of H2SO4in the H2SO4‾HNO3mixture was increased to 2:1, these materials also dissolved within 2 h. Quantitativeness of the dissolution was checked by the potentiometric determination of uranium and/or plutonium contents in these solutions. The results were in good agreement (±0.5%) when compared with the values obtained by the well-established dissolution method. During the fabrication of fuel (plutonium-rich mixed carbide) for the fast breeder test reactor, a large number of fuel samples were analyzed by using the above method of dissolution for the chemical quality control. Presuming the possibility of formation of small amounts of oxalic and mellitic (benzene hexacarboxylic) acids during the process of dissolution of carbides, the effect of the presence of these organic species on the potentiometric determination of uranium and plutonium was studied.

ISSN:0029-5450    

DOI:10.13182/NT87-A34010

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

A new family of ion exchange and sorption media has been developed and applied for the removal of radioactive contaminants from aqueous streams in nuclear power plant operations. The general principle in the development of these materials is optimization of their selectivity for species that significantly contribute to the radioactivity of these streams (e.g., cesium, iodine, and cobalt) in the presence of a large excess of other ions (e.g., sodium, potassium, magnesium, calcium, chlorine, and SO4). This results in improved effective capacity and service lifetime of these new materials compared with the performance of conventional broad-spectrum ion exchange resins. Other advantages include higher decontamination factors, shorter contact times, greater stability, and convenience of disposals. Examples of the new materials include Durasil™10, a high-capacity ion exchange medium for cesium and strontium, and Durasil™60 and 70, which are highly effective in the removal of iodine and cobalt, respectively. The performance of these new media has been characterized in laboratory studies, engineering-scale demonstration tests, and 1 to 2 yr of experience with the Durasil™media in routine waste-water treatment in several nuclear power plants.

ISSN:0029-5450    

DOI:10.13182/NT87-A34011

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor