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Graphite Barriers for Nuclear Used Fuel Repository Containers

IP.com Disclosure Number: IPCOM000224161D
Publication Date: 2012-Dec-11
Document File: 2 page(s) / 54K

Publishing Venue

The IP.com Prior Art Database

Abstract

While a strong safety case can be made for the NWMO reference UFC, the NWMO has recently initiated a program to investigate non-reactive, physical barriers external to the copper outer barrier, which would enable an improvement to the long-term predictions of container lifetimes. It is anticipated that such a barrier may help the container to pass through the relatively short aerobic period (i.e. initial 10 to 1000 y) with a higher degree of predictability, prior to the establishment of anaerobic conditions that will characterize the long life of the repository.

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Graphite Barriers for Nuclear Used Fuel Repository Containers

1.0   Introduction

The Nuclear Waste Management Organization (NWMO) was established in 2002 in accordance with the Nuclear Fuel Waste Act to assume responsibility for the long-term management of Canada's used nuclear fuel.

Adaptive Phased Management (APM) is the approach adopted by Canada for the long-term management of used nuclear fuel.  APM is a management and technical program designed to incorporate evolving knowledge into the various project phases.  This ensures best practices are used since APM has multi-generational timelines.  The APM program involves siting, engineering, construction, operations, long term monitoring and eventual decommissioning of a centralized underground used nuclear fuel storage facility in Canada.

The APM program’s engineering design is based on a generic reference concept for used fuel retrieval, transportation, packaging and placement in a deep geologic repository. A major engineered component of the reference design is the Used Fuel Container (UFC) in which used fuel bundles will be packaged.  The current cylindrical reference container is approximately four meters long and one meter in diameter, and consists of a one hundred millimetre thick inner steel vessel and a 25 millimetre thick outer copper shell. The total weight of the vessel is approximately 16.8 tonnes.

In the anaerobic conditions anticipated for a deep geological repository, copper is an excellent corrosion resistant material and its long-term corrosion behavior has been studied over the past 20 years for used fuel repository containers with favourable results. Currently, several international nuclear waste management programs have selected copper as a corrosion barrier for a deep geological repository.

2.0   Background: Used Fuel Container Reference Design

The current reference design UFC is manufactured using conventional techniques for both the inner steel vessel and the outer copper shell. The inner steel vessel provides the structural strength, sufficient to withstand geological scenarios such as glaciations, while the outer copper shell provides the corrosion barrier. Current research reveals that a relatively thin copper shell would provide sufficient corrosion protection for the repository lifetime; however, owing to limitations of conventional manufacturing methods, the copper shell must be produced as a thick separate vessel to maintain its structure during handling. Such a separate inner/outer vessel design also requires the two individually manufactured vessels to be assembled together, adding additional complexity and cost to the manufacturing procedure.

The reference design of the UFC is a technically feasible design; however, it may not represent the optimum UFC design for Canada’s unique CANDU fuel bundles, their fuel owners, and Canadians. Current investigations are underway to create an optimized, cost-effective UFC that maintains or enhances ...