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SUMMARYThe present report is one of a series of three. The series provides an independent technical review of certain aspects of the GOTH-SNF code that is used for accident analysis of the multicanister overpack that is proposed for permanent storage of spent nuclear fuel in the planned repository at Yucca Mountain, Nevada. The work documented in the present report and its two companions was done under the auspices of the National Spent Nuclear Fuel Program. The other two reports in the series are DOE/SNF/REP-087 1 and

This document was developed and is controlled in accordance with NSNFP procedures. Unless noted otherwise, information must be evaluated for adequacy relative to its specific use if relied on to support design or decisions important to safety or waste isolation. SUMMARYThe present report is one of a series of three. The series provides an independent technical review of certain aspects of the GOTH_SNF code that is used for accident analysis of the multicanister overpack (MCO) that is proposed for permanent storage of spent nuclear fuel in the planned repository at Yucca Mountain, Nevada. The work documented in the present report and its two companions was done under the auspices of the National Spent Nuclear Fuel Program. The other reports in the series are DOE/SNF/REP-088 and DOE/SNF/REP-089.This report analyzes the model for flow through the fuel elements that is documented in the SNF report titled MCO Work Book GOTH_SNF Input Data. 1 Reference 1 combined the multiple parallel paths through which the hot gases flow vertically inside the MCO into simpler paths. This report examines the assumptions used to combine the paths and concludes that there are other ways to combine the paths than the one used by GOTH_SNF. Two alternatives are analyzed, and the results are compared to those from the model used in GOTH_SNF. Both alternatives produced a higher pressure drop from the top to the bottom of the flow channel for a given flow velocity than did the approximation used in GOTH_SNF. Therefore, for a given pressure drop, the flow velocity given by the GOTH_SNF approximation will be lower than that from either of the two alternatives.The practical consequences of the differences in flow rate are not obvious. One way to evaluate the consequences is to repeat an important MCO calculation on GOTH_SNF using an altered hydraulic diameter (the one that produces the highest pressure drop for a given flow velocity) and see if the conclusions about the safety of the MCO are changed.The NSNFP chemical reactivity analysis provides information about the performance of the Multi-Canister Overpack (MCO) loaded with N-Reactor spent fuel in the repository environment relative to the potential for intense chemical reactions on the corroded portions of the fuel elements. The review task was an independent review of the approach and reasonableness of results from the NSNFP chemical reactivity analysis. The chemical reactivity analysis performed by the NSNFP is not a part of the primary licensing strategy for U. S.

The upgrade and redesign of a fluidized-bed denitrator for production of uranium trioxide from uranyl nitrate solution is discussed. The success of the project in improving process efficiency and personnel safety is also addressed based on subsequent operation. CONTENTS