Thermal performance of a buried nuclear waste storage container storing a hybrid mix of PWR and BWR spent fuel rods; Revision 1

Abstract

DISCLAIMERTrus documen: was prepared 25 an acccourtt of work sponsored bv an agency of the United States Government Neither the United 5ta:&5 Government nor the University of California nor any of their employees, makes anv warranty express or implied or afsumes any legal liability or responsibility for the accuracy, completeness, or usefulness 01 <*nv iniormafior. apparatus product or process disclosed, or represents that its use would not infringe privately ov-i; rights Reference herein to anv specific commercial products, process, or service bv trace name, trademark, manufacturer, or oth«rv.-:5«= dees rot r.ecessarJv constitute or nnply its endorsement, recommendation or favoring bv the United State* Government or the Uruversitv o: California. The r.ews and opinions of author* expressed hereir dc net necessar.lv state or reflect tho-se o: the Uruted States Government or the University o: California, and snail not be used for ad versing or proc-jc: endorsement purposes Trus report has beer-reproduced chrectlv rrorr. the best available copv PageRgure 24. Backfilling the annulus with loosely packed bentonite raises the peak temperatures over 50°C above the case with no backfill. Backfilling the annulus with firmly packed bentonite only raises the peak temperatures by about 5°C 53Rgure 25. Using realistic contact thermal resistances rather than ideal values does not change the peak temperatures 54Rgure 26. The peak temperature of the fuel cladding for the 5-year fuel case, 411°C, occurs about 8 months after emplacement 55Rgure 27. isotherms for the 5-year fuel case at about 8 months after emplacement _ 56Rgure 28. The peak temperature of the fuel cladding for the emissivity case with its lower emissivity on the inside surfaces is 346°C 57Rgure 29. Isotherms for the emissivity case near the time of peak temperature show sharper gradients in structure than in the reference case 58Rgure 30. When compared with the reference case, the peak temperatures increase by as much as 10°C by assuming the lower emissivity for the inside surfaces 59Rgure 31. The peak temperature of the fuel cladding for the case with increased fuel conductivity is 322°C _ 60Rgure 32. Isotherms for the fuel conductivity case show much less temperature gradient in the fuel boxes 61 PageRgure 33. The use of fuel pack thermal conductivities derived from Battelle's measured fuel bundle temperature profiles, lowers the peak cladding temperatures by 8 to 15°C 62Rgure 34. The peak temperature of the fuel cladding for the gas fill case is 335°C. Thermal radiation is still the predominant heat transfer mode._ " 63Rgure 35. Isotherms for the gas fill case at about 3 yr after emplacement 64Rgure 36. The peak temperature of the fuel cladding for the "best model" analysis, including: fine-zoned mesh of tuff, improved fuel conductivity, 0.5 internal surface emissivity, and gas-fill conduction, is 336°C 65Rgure 37Isotherms for the best model analysis at about 3 yr after emplacement 66Rgure 38. The peak temperature of the fuel cladding for the SCP layout case, ...