CASKLOAD - Optimize Cask Loadings and Manage Fuel Pool Axel Becker 2011 International Users Group Meeting Stockholm, Sweden | May 24-25, 2011 Overview • Dry Casks for Intermediate Storage of Spent Fuel • Cask Loading Problem • Cask Design Criteria • Cask loading sample study • CMS codes for Back-End Applications May 24-25, 2011 International Users Group Meeting Dry Casks for Intermediate Storage Dry cask storage is one concept for intermediate storage (about 30-40 years) of spent fuel assemblies. The dry cask concept is used in Germany. Similar concepts are applied in several other countries. May 24-25, 2011 International Users Group Meeting Intermediate Storage Facilities in Germany Intermediate Storage Facilities in Operation http://www.bfs.de/de/transport/gv/dezentrale_zl/karte.html http://www.kkw-gundremmingen.de/ May 24-25, 2011 International Users Group Meeting Fuel Assembly Storage on Site Spent fuel assemblies are stored in the fuel pond first, then loaded into casks and the casks are stored in the intermediate storage facility. Reactor Building Fuel Pond Intermediate Storage Facility Cask Pond Cask Distance 150 m http://www.kkw-gundremmingen.de/popup_grafik.php?id=kkw_t5_1 May 24-25, 2011 International Users Group Meeting Cask Loading Problem Reactor Operation Phase Cask Loading Campaigns Final plant Restriction due shutdown to Fuel Pond Capacity Plant Post-Operation Phase Final plant shutdown All nuclear fuel High Post-Operation unloaded Costs Minimize post-operation phase! May 24-25, 2011 International Users Group Meeting Optimize Cask Loadings Goals: • Minimize costs for dry casks • Minimize plant operation costs after final plant shutdown • Manage fuel pool – Restriction due to fuel pool capacity – Minimize number of fuel assemblies in pool Parameters: • Different cask types (e.g. different vendors) • Different cask designs • Cask loading dates • Full loading vs. partial loadings • etc. May 24-25, 2011 International Users Group Meeting Cask Design Cask Design Requirements ⇒ • Max. Temperature ( Fuel assembly (FA) decay heat limit) • Subcriticality (⇒ max. initial enrichment, min. burnup) • Max. radiation at cask surface (⇒ FA neutron/gamma sources limit) Cask Design by Cask Vendor Vendor designs regions having different Cask Acceptance Criteria (CAC) for fuel assemblies to improve cask utilization. BWR sample PWR sample May 24-25, 2011 International Users Group Meeting Cask Acceptance Criteria (CAC) Base criteria • Max. initial enrichment, min. and max. FA burnup • FA decay heat, neutron/gamma sources (time-dependent) Additional considerations • CAC are region dependent • One physical cask type can have different region layouts • Only specific partial loadings are allowed • CAC might be interdependent between regions May 24-25, 2011 International Users Group Meeting Cask Load Planning Assign each discharged fuel assembly (FA) to a specific position in a cask to meet cask acceptance criteria and optimize costs. Discharged FAs All FAs unloaded Final plant from Pool shutdown Restriction due to Spent Fuel Pool Capacity High Post-Operation Costs Done by CASKLOAD May 24-25, 2011 International Users Group Meeting Cask Load Studies Several studies for BWR-NPP and PWR-NPP have been performed. One BWR study is presented here. Scope: 1.Projection of plant operation with CASMO/SIMULATE until end of plant life time and determination of discharged FAs for each cycle 2.Calculation of FA spent fuel properties with SNF like decay heat, radiation, cask acceptance criteria etc. 3.Assigning each FA to a specific cask at a certain loading date and a certain cask region with CASKLOAD. May 24-25, 2011 International Users Group Meeting Cask Types Heterogeneous Cask Loading with Dummy-FA All BWR cask types considered Heterogeneous Cask Loading Homogeneous Cask Loading D D D D here are physically identical having U U U U U U U U D U U U U D 52 FA positions but can be utilized U S S S S U U U U U U U for different loadings D U U S S U U D U S U U U U S U U U U U U U U U D U S S S S U D • homogeneous loading (52 U-FAs) U S U U U U S U U U U U U U U U D U S S S S U D U S U U U U S U • heterogeneous loading U U U U U U U U D U U S S U U D U S U U U U S U 52 FAs : 36 U + max. 16 S U U U U U U U U D U U U U D U S S S S U S = e.g. special U-FA with higher BU U U U U U U D D D D • heterogenous loading UU UU UU U U 32 FAs: 20 U + max. 12 S and 20 Dummies May 24-25, 2011 International Users Group Meeting Fuel Assembly (FA) Properties 37 months after NPP Number of FAs fulfilling Cask Acceptance Criteria (CAC) shutdown: 800 32 hete S pos CAC are fulfilled for 700 52 hete S pos all FAs for the S 600 position of the 32 500 loading. 400 No. of FAs => 300 first feasible point in 200 time to load all FAs 100 into casks 0 0 10 20 30 X 40 50 60 Months after Reactor Shutdown May 24-25, 2011 International Users Group Meeting Cask Loading Scenarios Theoretical scenario: When trying to load all FAs exactly 37 months after NPP shutdown a solution was found: – 5 heterogenous 52 loadings – 16 heterogenous 32 loadings ⇒ 21 casks in total Realistic scenarios A and B: One week (A) or two weeks (B) loading time per cask are taken into account May 24-25, 2011 International Users Group Meeting Realistic Scenario A and B Optimal solutions: Scenario A -11w < X <+10w 20 casks (15x32er+5x52er= 728) Scenario B -11w < X <+22w 17 casks (7x32er+10x52er = 728) Scenario A: loading one cask per week Scenario B: loading two casks per week May 24-25, 2011 International Users Group Meeting Codes for In-Core and Back-End SNF Spent Nuclear Fuel Properties CASMO 5 Isotopic Data Power CASKLOAD SIMULATE Optimization of History Cask Loadings In-Core Analysis Back-End Analysis May 24-25, 2011 International Users Group Meeting CASKLOAD CASKLOAD supports the engineer to plan loading spent nuclear fuel from fuel pond into dry storage casks and optimizing cask loadings due to criteria: Total Costs and APRT (Average Pool Residence Time) User Input CASMO5 SIMULATE CASKLOAD SNF Fuel Property File May 24-25, 2011 International Users Group Meeting Summary • CASMO / SIMULATE / SNF provide an integrated approach for back-end calculations – with high accuracy (resolution in space and time) – and easy-to-use. • CASKLOAD supports the engineer to plan cask loadings and optimizing it due to selected criteria. May 24-25, 2011 International Users Group Meeting May 24-25, 2011 International Users Group Meeting May 2010.