Economic and Environmental Aspects of Long-term Spent Fuel Storage (UK Perspective)

Transcription

1 Economic and Environmental Aspects of Long-term Spent Fuel Storage (UK Perspective) Presentation to the Contact Expert Group workshop on isolation and Disposal of Radioactive Waste, June 2006, Olkiluoto, Finland Presented by P N Standring Slide 1 Scope Background NPPS Fuel types Fuel Storage Fuel Behaviour Spent Fuel Management Strategies Long-term Advanced Gas Reactor (AGR) Storage Studies Utility based Scottish Nuclear Limited ( ) Backend Service Provider BNFL (2004) Economics & Environmental Slide 2 1

2 Nuclear Power Plants - UK (Decommissioning) (Decommissioning) (Decommissioning) Slide 3 Background Types of Spent Fuel Magnox Advanced Gas Reactor Pressurised Water Reactor (PWR) Slide 4 2

3 At Reactor Spent Fuel Management Magnox AGR PWR Dry to Wet transition (apart from Wylfa NPP complete dry route) Fuel stringers de-splittered (potential for damage to Magnox Can) Wet Storage Pools (Limited 1-2 Years) Wylfa NPP (5 vault- stores 3x Co2 cooled, 2 x Air Cooled) Stringer (7-8 elements) dismantled into individual elements (dry route) Buffer Storage Tubes -CO 2 Cooled (varies generally very limited (maximum~6 months)) Dry to Wet transition Wet Storage Pools (varies between reactors, 6-12 months) Wet Storage Pool (Lifetime) Slide 5 Spent Fuel Behaviour in Storage Fuel Type Magnox AGR PWR Fuel Cladding Magnesium Alloy (Magnox-A 180) Stainless Steel (20Cr:25Ni:Nb) Zircaloy Wet Storage Corrodes to Mg(OH) 2 + H 2 Rate effected by water impurities Elements 1-5 susceptible to inter granular attack from chloride ions in un-dosed water. Failure mode is a pin hole releasing mobile caesium, but not fuel Negligible corrosion in water Dry Storage <350ºC negligible corrosion in CO 2 Pitting attack in air >50% RH Elements 1-4 susceptible to inter granular stress corrosion cracking through nitric acid attack (>50,000 vpm) Pin hole (early stages would lead to crack propagation) Thermal Creep (Zr-4) Hydride re-orientation Slide 6 3

4 Background - recent history Power generators have always had the decision over the back end policy adopted Scottish Nuclear Limited (SNL) and Nuclear Electric Limited (NEL) were formed out of the first privatisation of the electricity industry National Power in 1980s (retained as state owned companies) SNL investigated alternatives reprocessing (~ ) Mid 1990s Magnox reactors removed from SNL and NEL portfolios to form Magnox Electric under BNFL group Lifetime spent fuel management contracts were signed with SNL(1995) and Nuclear Electric Limited (1997) SNL & NEL privatised 1996 formation of British Energy Slide 7 Background - recent history The restructuring of British Energy plc was completed on 14th January For fuel loaded to reactor post restructuring the title of the fuel transfers to British Nuclear Group Sellafield Ltd on delivery to Sellafield. The formation of British Nuclear Group in April 2004 in readiness for the management and operation of UK nuclear sites to be competed; in-line with the provisions made in the Energy Act Formation of the Nuclear Decommissioning Authority (NDA) in April 2005, under the Energy Act 2004, to take responsibility for the UK s nuclear legacy. The NDA approach with respect to AGR spent fuel management will be to establish a national review as part of their consultation on the longer term options for the fuel. In the mean time the current strategy for managing AGR spent fuel, i.e. use of Thorp Receipt and Storage, is a bridging solution to maintain power generation activities pending the outcome of the NDA review. Slide 8 4

5 Spent Fuel Management Strategies - UK Magnox (British Nuclear Group Sellafield Limited) Closed Cycle (Magnox fuel is programmed to be reprocessed by end 2012) PWR (British Energy) Open Cycle (Long term storage at reactor pending direct disposal (>2075)) AGR (British Nuclear Group Sellafield Limited) Closed Cycle (Reprocess AGR fuel until 2010/11) Open Cycle (Non-reprocessed AGR fuel will be stored in existing facilities (Thorp Receipt and Storage) pending the out-come of the National Review) Future? (National Review of Long Term Spent Fuel Management (initiated by Nuclear Decommissioning Authority April 2006)) Slide 9 Health Warning Study Information The information provided does not prejudice the out-come of the national review on spent fuel management The information was relevant at the time of the study and reflects a particular set of circumstances Costs are dependent on the underlying assumptions Volume of spent fuel to be stored Scope Regulatory requirements Company standards (BNGSL- 5mSv worker dose for new plants) UK prices Slide 10 5

6 AGR Long Term Storage - Studies Report two studies evaluating the long term storage of AGR fuel Utility based undertaken by Scottish Nuclear Limited ( ) Back end service provider British Nuclear Fuels plc (2004) Spent Fuel Waste or Asset? U and Pu from 1t of 40GWd/tU PWR fuel could provide an energy equivalent of 4GWd(e) Slide 11 AGR Options Study Torness NPP (1993) Scoping of Alternative Options Vault Storage (Modular Vault Dry Store (MVDS) Metal Cask Storage Concrete Container Storage (OPG DSC system) Pool (or pond) Storage Dry Well Storage MVDS Taken Forward (Option 1) Wet route via drying plant to dry storage (Option 2) Wet route with dry bottle, via drying plant to dry storage (Option 3) Dry route, via drying plant to dry storage (Option 4) Business as usual (Reprocessing) (Option 1)Wet route via drying plant to dry storage Slide 12 6

7 MVDS PAKS, HUNGARY (1-11 VAULTS) Slide 13 Factors which influenced the Technology/Economics Limited by current site licence Couldn t transfer fuel between sites (i.e. store at each site) Secondary Waste (i.e. couldn t remove graphite sleeve) Storage capability at reactor Technology adopted would need to be able to accommodate 100 day cooled fuel Storage of whole fuel elements Capacity Residual moisture (Dry Storage) Slide 14 7

8 Order of Costs - Torness Study % to Option Option 1 Option 2 Option 3 Option 4 % to Option 1 N.B. Options 1-3 do not include final conditioning costs c.f. Option 4 Slide 15 Environmental Torness BPEO (technique - multi-attribute analysis) Attribute Group Attribute Cost Construction Operating Radwaste management Decommissioning Flexibility Plant Outage Final Disposal Options Safety Worker Dose Public Dose Non-radiological Technology Maturity of Technology Public Opinion Monitoring NIMBY Legacy Perceived Risk Slide 16 8

9 Environmental Torness BPEO (examples of out-put) Safety (Worker Dose) Option 1 Option 2 Option 3 Option 4 Ops) Public Opinion 0.1mSv/yr.Comparison to PAKs experience 6.3µSv/yr 0.13mSv/yr 0.14mSv/yr 0.6mSv/y.added for comparison (study predates Thorp The ability to monitor was seen to be important for the long term surface storage of spent fuel in comparison to reprocessing A similar reaction was expressed in relation to Legacy, but with an increased weighting Slide 17 Differences between Torness & Sellafield study Dismantling Dismantling of spent fuel and production of secondary waste already covered under site licence Production dismantler (fuel consolidation) since 1986 Existing Facilities There are large central wet spent fuel storage facilities in operation at Sellafield Five operational Cost data Environmental aspects Socio Economic Sustainability Slide 18 9

10 AGR Dismantling Storage Economics Spent Fuel received to Sellafield site as whole elements >180 days cooled elements are dismantled into component parts (fuel pins, graphite sleeve and structural components) Dismantling leads to an three fold increase in storage density Removal of graphite sleeve is beneficial for fuel drying if dry stored Three fold less use of resources for fuel storage Slide 19 Spent Fuel Storage Existing Facilities Thorp Receipt & Storage Fuel Handling Plant Slide 20 10

11 AGR Options Study Sellafield (2004) Scoping of Alternative Options (Option 1) Dismantle in FHP, Store in existing pond facilities (Option 2) Use of FHP till 2015, Receipt, dismantling and storage in TR&S >2015 (Option 3) Dismantle in FHP into sealed canisters store in existing facilities (Option 4) Dismantle in FHP till 2015, >2015 fuel stored undismantled in existing facilities (Option 5) Dismantle in FHP, Long term storage in dry casks (Option 6) Torness option (Store fuel undismantled in an MVDS) (Option 7) Long term storage in an innovative store Sub-Options (E.g. Option 1) FHP, existing grid, existing storage system FHP, optimised grid, existing storage system TR&S, existing grid, existing storage system and stack height TR&S, existing grid, optimised storage system, existing stack height TR&S, existing grid, optimised system and increased stack height TR&S, optimised grid, optimised system and increased stack height TR&S, existing grid, optimised storage system, existing stack height Slide 21 Order of Costs Sellafield study Benchmark = Cost of dry storage in Germany (comparable to Option 5) % Option Benchmark Option 2 Option 4 Option 6 S1 Slide 22 11

12 Environmental BPEO (technique - multi-attribute analysis) Attribute Group Attribute Impact on other site activities Cost Lifetime Sustainability Environmental & Safety Worker Dose Public Dose Non-radiological Resource use Disturbance/nuisance Secondary Waste Technology Maturity of Technology Public Opinion & Social Stakeholder consultation Impact on jobs Impact on local community Slide 23 BPEO (Radiological) -AGR Spent Fuel Management The conclusions drawn from life cycle analysis of the open and closed nuclear fuel cycles have shown the Human Irradiation risks and non-active burdens to be comparable The risks ~8-9E-09 are considered small per TJ The generic question of whether one approach is better than the other from a Best Environmental Option (BEO) approach reduces to issues such as policy, cost and whether facilities are currently available Slide 24 12

13 Resources Major Material Changes (Example) Area Change Material Volume /m3 Pond Storage AGR Containers Pro Energy - Stainless Steel Concrete Reprocessing Operations Pro Energy Uranium (AGR) Repro Wastes LLW Packages (Ht containers) Con^ LLW Mild Steel Weight /t Energy /Gwhr -1 0 Product Storage Fuel Encapsulation Direct Disposal ILW drums Operations HA Operations Vit containers Pu cans U cans Encapsulation into disposal canisters Operations Vit Containers Con^ ILW Pro Energy Stainless Steel OPC HA Liquor Pro Energy Stainless Steel PuO2 UO3 Stainless Steel Pro Energy Cast iron Copper HAW Fuel Disposal Canisters HAW + ve Slide 25 Major Discharges (Comparison to reprocessing) Area Change Species (dominant) Pond Storage No Change Reprocessing AGR fuel Total Aerial reprocessed (I 129,Kr 85,C 14 ) Weight /t CG Dose /µsυ Coll Dose / man Sυ NOx Total Liquid (Ru 106,Ce 144, I 129,C 14, Cs 137 ) Repro Wastes LLW No change Nitrate/Nitrite ILW No change HAW Operations NOx - - Product Storage Fuel Encapsulation Direct Disposal No change Unknown Vit Containers Se 79 Fuel Disposal Canisters Se 79 Slide 26 13

14 Typical annual doses to those exposed to radiation (UK) 20mSv ~2.5mSv Regulatory dose limit for workers Average dose to us all from exposure to natural background radiation (8mSv in Cornwall) ~ 2mSv Average additional dose to airline crews through exposure to cosmic rays ~1.3mSv Average dose to a Sellafield radiation worker from occupational exposure (Thorp average about half ~ 0.6mSv) 1mSv Dose limit for members of the public from practices. ~0.2mSv Highest (critical group) dose to public from Sellafield * ~0.6µSv Critical group dose to public from TR&S operations *i.e. those believed to be most at risk due to extreme behaviours/exposure patterns Slide 27 Summary Overview of the UK position spent fuel management Provided examples of a utility and back end service provider studies It s a snap shot in time and should be considered as work in progress The strategy to be adopted is pending the national review on spent fuel management initiated by the Nuclear Decommissioning Authority Slide 28 14