Coordinated Research Project - T13014
Demonstrating Performance of Spent Fuel and Related Storage System Components during Very Long Term Storage
The total amount of spent fuel that has been discharged globally is more than 320 000 tonnes of heavy metal (t HM). Of this amount, over 95 000 t HM have already been reprocessed, and more than 225 000 t HM are stored in spent fuel storage pools at reactors or in away-from-reactor (AFR) storage facilities. Many spent fuel storage pools are approaching their full capacity, and AFR storage facilities are being regularly expanded both by adding modules to existing dry storage facilities and by building new facilities. In addition to expanding capacity, most countries must now plan for lengthening storage periods. Indeed spent fuel may have to be stored for very long periods, i.e. 100 years or more. Moreover, target discharge burnup is steadily increasing. This results in increased fission gases and cladding corrosion, which, in turn, lead to increased cladding stress.
The first dry storage facilities have already reached the end of their originally licensed periods. Because final repositories for spent fuel or high level waste (HLW) will not be in operation until the 2020s at the earliest — and then only in a few countries — licenses for storage facilities will need to continue to be extended or renewed. To do so, it is important to assess the performance of spent fuel and related important storage system components in order to confirm the viability of extended storage. To support such assessments, some examinations of spent fuel performance have taken place. The USA has examined a storage cask and its contents after 15 years of storage to obtain data in support of license extensions for low burnup fuel and has initiated an Extended Storage Collaboration Program (ESCP). Other countries, including Japan, are expected to also perform long term monitoring to demonstrate the integrity of stored spent fuel.
At an initial IAEA planning meeting held in August 2011, international experts in spent fuel performance confirmed the value of further coordination and development of international efforts to demonstrate the performance of spent fuel and related important storage system components as durations extend. Understanding that the ESCP effort cited above provides a broad context for this work, it was agreed that this proposal for an IAEA research coordination project (CRP) could make important contributions by targeting specific needs. Accordingly, experts examined on-going gap analyses (gap between anticipated technical needs and existing technical data) in order to identify the specific research objectives and corresponding specific activities listed in the following sections 4 and 7. An indication of support for this proposal is that extra-budgetary funding for this work will be provided through the US Peaceful Uses Initiative. Since the Nuclear Energy Agency plans to propose a 2013 workshop on extended spent fuel storage matters, the IAEA will coordinate appropriately with NEA counterparts in this regard. This CRP will also coordinate these specific activities with the broader scope of the on-going SPAR-III CRP. While a full range of spent fuel types and conditions are deployed around the world, this CRP will focus on existing systems (in lieu of new designs) and specifically light water reactor fuel in dry storage. In many cases, lessons learned may be applicable to other conditions including new designs.
Accordingly, this proposal is to conduct a CRP to increase the coordination among such efforts (e.g. joint IAEA-ESCP-NEA meetings) so that they yield increased joint benefits for all participants and generate results in a form that is useful to countries considering or starting nuclear power programmes as well as to countries with established nuclear power programmes (and existing accumulations of spent fuel). The overall result should be a widely shared improvement in the nuclear power community’s ability to support the extension of licences for spent fuel storage (CRP results are also expected to facilitate subsequent transport and disposal).
IAEA international conferences on spent fuel management have concluded that effective spent fuel management is “now one of the more important factors influencing the future of nuclear energy.” Given the need to renew storage facility licenses described above, it is important to demonstrate spent fuel performance to confirm the viability of very long term spent fuel storage.
The overall objective of this CRP is to support and share improvement in the nuclear power community’s technical basis for LWR spent fuel management licences as dry storage durations extend. This will involve developing
- a network of experts working on current research projects to demonstrate the long term performance of spent fuel;
- experimental data on the very long-term performance of spent fuel and related important storage system components;
- computational and experimental methods to adequately demonstrate very long-term performance;
- capability to assess the impact of high burn-up fuel on very long-term storage.
This work will contribute to technical basis documentation for demonstrating the performance of spent fuel and related important storage system components over long durations (CRP results are also expected to facilitate subsequent transport and disposal), and thereby facilitate the transfer of this knowledge to others including to newcomer countries.
Specific Research Objectives:
- Evaluate mechanisms for stress corrosion cracking (SCC) as a way of breaching spent fuel canisters in a marine environment.
- Evaluate monitoring for stress corrosion cracking (SCC) as a mechanism for breaching spent fuel canisters in a marine environment (in order to evaluate the confinement capability of welded stainless steel canisters and to protect the integrity of the contents).
- Evaluate degradation of the spent fuel and the confinement capability of the spent fuel canister or container (avoiding penetrations that could compromise integrity).
- Determine the effect of drying and storage on spent fuel cladding behaviour during subsequent normal transport (particularly effects that might impact the ability to handle fuel after that transport).
- Determine whether predictive models based on laboratory experiments adequately predict behaviour of full assemblies, including the interaction of the rods with assembly hardware under prototypic storage conditions (given that full assemblies have a range of characteristics relevant to storage and transport).
- Evaluate the confinement capability of concrete cask systems, including enabling examination of existing actual casks.
- Evaluate long-term confinement in spent fuel casks, focusing on the bolted lid for normal and accident conditions during storage and transport.
- Evaluate long-term confinement in spent fuel casks, focusing on metal gaskets for normal and accident conditions during storage and transport.
- Evaluate long-term neutron shielding capability.
- Evaluate system effects analytically by integrating important components of spent fuel storage demonstration in a “prototypic” manner.
Expected Research Outputs:
The research outputs from the CRP will be published as an IAEA technical document with the same title at the end of the CRP cycle.
Expected Research Outcomes:
- Accomplishing the above objectives contributes to successful development of an aging management program, monitoring requirements and inspection/replacement frequency/intervals, as well as data sets suitable for validation of mechanistic models.
- Completion of vibratory testing cited below supports post-storage licensing, including transport- and disposal related considerations.
- Completion of work on bolted systems and metal gaskets cited above supports post-storage licensing, including transport- and disposal-related considerations.
- Completion of component-level testing will guide the necessity and content of subsequent full-scale testing.
- Development of monitoring and inspection techniques cited above could support future monitoring and inspection capability that currently doesn’t exist. Data would be gained and used to support post-storage licensing.
The following ten specific activities directly correspond to the ten specific research objectives listed in section 4 above.
- Obtain representative (e.g. archived) canister material samples; complete laboratory investigation of mechanisms related to stress corrosion cracking.
- Develop techniques and deploy systems to monitor for stress corrosion cracking at a nuclear site with dry storage casks exposed to a marine environment.
- Develop techniques and deploy systems for detecting temperature, moisture, oxygen, krypton, xenon inside the fuel-containing cavity.
- Develop and conduct tests for hydride-reoriented fuel rods under simulated normal transport vibratory conditions, to look for failure.
- Develop a small (e.g. 2-3 assembly) long-term rod behaviour test in a hot cell, simulating expected temperature decrease for a cask [including pre- and post-characterization, realtime monitoring on HBU (60 GWd/MTU) rods with initial temperature of at least 400 degrees Celsius].
- Survey/develop techniques for remote inspection of concrete cask systems, checking for temperature, salt, corrosion, and integrity.
- Survey/develop techniques for inspecting pre-stress release of bolted cask closure systems.
- Survey/develop information on long-term performance of metal gaskets.
- Survey/develop information on degradation of polymers (neutron shielding).
- Develop functional requirements and analyses (pros/cons) of a full-scale demonstration test, building on the above “components” of an overall demonstration program.
List of potential participating countries:
Argentina, Armenia, Australia, Bangladesh, Belgium, Brazil, Bulgaria, Cameroon, Canada, Chile, China, Croatia, Czech Republic, Democratic Republic of Congo, Estonia, Finland, France, Georgia, Germany, Hungary, India, Italy, Japan, Jordan, Korea – Republic of, Kuwait, Latvia, Lithuania, Mexico, Netherlands, New Zealand, Nigeria, Norway, Pakistan, Poland, Romania, Russian Federation, Saudi Arabia, Serbia, Slovakia, Slovenia, South Africa, Spain, Sweden, Switzerland, Thailand, Turkey, Ukraine, United Arab Emirates, United Kingdom, United States of America, Vietnam.
You can download the printable file here.
Standard IAEA Proposal forms are available on our website: http://www-crp.iaea.org/html/forms.html