ISSN:0029-5450    

DOI:10.13182/NT87-A33891

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

ISSN:0029-5450    

DOI:10.13182/NT87-A33892

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

Various phenomena governing the course of large-and small-break loss-of-coolant accidents in light water reactors and affecting the key parameters such as peak cladding temperature, and timing of the end of blowdown, beginning of reflood, and complete quench have been identified. The models and the correlations for these phenomena in the current literature, in advance codes, and as prescribed in the current emergency core cooling system methodology as outlined in Appendix K of CFR50 have been reviewed. It was found that the models and correlations in the present best-estimate codes such as TRAC or RELAP5 could be made more realistic by incorporating some of these models from the literature. However, an assessment program will be needed for the final selection of the models for the codes.

ISSN:0029-5450    

DOI:10.13182/NT87-A33893

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

A small-break loss-of-coolant accident (LOCA) caused by a stuck-open power-operated relief valve is one of the important contributors to nuclear power plant risk. A pressurizer surveillance system was designed to use a microcomputer to prevent the malfunction of the system; the effect of this improvement has been assessed through probabilistic risk assessment. The microcomputer diagnoses the malfunction of the system by a process-checking method and automatically performs the backup action related to each malfunction. This improvement means that we can correctly diagnose“spurious opening,”“failure to reclose,”and“small-break LOCA,”which are difficult for operators to diagnose quickly and correctly, and by taking automatic backup action we can reduce the probability of human error.

ISSN:0029-5450    

DOI:10.13182/NT87-A33894

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

A 200% cold-leg break accident in a Westinghouse four-loop RESAR-3S plant has been analyzed using the best-estimate code TRAC-PD2/MODI/Version 27 with updates. Three TRAC calculations have been performed. The first calculation used the best-estimate or realistic initial and boundary conditions and scenarios and the other two calculations, one with and one without locked rotor resistance, used the licensing conditions. These calculations produced the peak cladding temperatures (PCTs) of 800.5, 1072, and 1153 K, respectively. Comparison of these results with the Westinghouse licensing calculations performed in accordance with the guidelines in Appendix K of 10CFR50 shows an overall safety margin of 663 K, of which 352.5 K is due to the conservative initial and boundary conditions and scenario. The remaining 310.5 K is due to conservative physical models. The locked rotor resistance contributed∼81 K to PCT.

ISSN:0029-5450    

DOI:10.13182/NT87-A33895

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

Aerosol samples consisting of fission products and elements of light water reactor structural materials were collected during laboratory-scale simulation of the heat-up phase of a core melt accident. The aerosol particles were formed in a steam atmosphere at temperatures of the melting charge between 1200 and 1900°C. The investigation of the samples by use of x-ray photoelectron spectroscopy (XPS) permitted the chemical speciation of the detected aerosol constituents silver, cadmium, indium, tellurium, iodine, and cesium.A comparison of the elemental analysis results obtained from XPS with those achieved from electron probe x-ray microanalysis revealed that aerosol particle surface and aerosol particle bulk are principally composed of the same elements. The compositions determined in dependence of the release temperature reflect the differing volatilities of the detected elements. Quantitative differences between the composition of surface and bulk have been observed only for those aerosol samples that were collected at higher melting charge temperatures. These samples show an enrichment of more volatile species at the particles’surfaces.In order to obtain direct information on chemical species below the surface, selected samples were argonion bombarded. Changes in composition and chemistry were monitored by XPS, and the results were interpreted under consideration of possible influences of the sputter process on the surface composition.

ISSN:0029-5450    

DOI:10.13182/NT87-A33896

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

The applications of nuclear technology in reactor siting with reference to earthquake prediction and fault exploration are discussed. The technique first used thin thermoluminescent dosimeters to monitor alpha particles from soil radon emanation; these dosimeters were later replaced by cellulose nitrate films and a self-fabricated spark counter. Data from a 2-yr observation of soil radon emanation correlated with earthquakes are presented graphically. Radon peaks appeared 5 to 20 days before earthquakes. A similar technique was also applied in fault exploration. The higher radon peaks appear at the location of the fault. This simple and inexpensive technique is particularly well-suited to nuclear reactor siting since the area of interest at the site is quite limited. The extension of this technique to the public communication program for a nuclear facility is also suggested.

ISSN:0029-5450    

DOI:10.13182/NT87-A33897

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

Egan’s theory of fuel management for in-core fuel cycles covers both integer and noninteger strategies, where exact integer fractions imply changing, for example, one-third of the core at a time. Various typical problems can be identified that focus on the dynamics of such in-core fuel cycles.In the first problem, one can specify the initial enrichment and hence initial reactivity of the reload fuel and the fraction (integer or noninteger) to be changed in the reload strategy. Starting from an allclean core, there is a sequence of cycle times, measured in, say, megawatt days per kilogram. For both integer and noninteger strategies, this sequence converges to an equilibrium cycle time that repeats unchanged; the convergence is quite rapid.On the other hand, the fuel manager may prefer to maintain the strategy at each reload, changing the same fraction of fuel assemblies but varying the initial reactivity (via enrichment variation) to secure constant equilibrium burnup or cycle time from the start. Egan showed, by numerical examples, that integer strategies do not converge but oscillate through the sequences of initial reactivities. Although this behavior is true for all integer strategies, it turns out that noninteger strategies do converge, albeit very slowly.Finally, what about varying the fraction of standard fuel assemblies reloaded in each cycle while keeping the burnup time constant? It appears that the sequence of such fractional reloadings is also convergent, for integer and noninteger cases, a fact that can be proved with the aid of the proof for the initial problem of varying cycle times. So the fuel manager would be advised to consider this third option, varying the fractional reload, rather than the second option, varying the initial reactivity or enrichment to achieve an equilibrium cycle.The present work is done in the context of a simple lumped model using a linear variation of reactivity with burnup. Future extensions could be made to allow perhaps for coast down and energy distribution coefficients. Nevertheless, the present analysis provides a simple theory to underpin conventional and more complicated computer studies of distributed systems.

ISSN:0029-5450    

DOI:10.13182/NT87-A33898

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

The one-dimensional diffusion model of leaching was developed on the basis of the Soxhlet-type leaching experiment of waste glass. Emphasis was placed on proposing a model for the growth of surface layers and for an immobilized reaction inside these layers. The equations derived from the modeling were solved numerically and the resulting equations were implemented in a computer code named LEACH. The computed and measured leach rates of sodium, cesium, calcium, and strontium were in good agreement under the Soxhlet-type leaching condition. The computed results revealed that the growth of surface layers, including the immobilized reaction, plays an important role in the leach rates of elements, because the diffusion coefficients of surface layers were much different from those of the bulk glass, and because for calcium and strontium the immobilized reactions affected their leach rates. Therefore, in order to predict the leach rates of waste glasses by using the proposed model, the time dependence of the growth of surface layers should be measured experimentally.

ISSN:0029-5450    

DOI:10.13182/NT87-A33899

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

ISSN:0029-5450    

DOI:10.13182/NT87-A33900

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor