PSI - Issue 19

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ScienceDirect ScienceDirect Structural Integrity Procedia 00 (2019) 000 – 000 Structural Integrity Procedia 00 (2019) 000 – 000 Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect

www.elsevier.com/locate/procedia

Procedia Structural Integrity 19 (2019) 346–361

© 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers. Multi-purpose canisters (MPCs) are being employed for dry canister storage of spent fuel at nuclear plant sites as a temporary approach until an interim or permanent dry storage site(s) is available. For storage in coastal or lakeside regions and even humid environments, the corrosive nature of the moist air with entrained chlorides can make the welded regions of the canisters susceptible to pitting and chloride induced stress corrosion cracking (CISCC). In this report we evaluate CISCC lifetimes of welded 316L stainless steel canister plates showing in excess of 19 times increase of laser peened panel sections vs. those left as-welded using ASTM G36 (2013) accelerated corrosive testing. Specifically cracks never developed or propagated into the laser peening area. We also provide measurements of residual stress in test plates and related calculations of stress intensity and depth expected in the full canister geometry. We discuss the relevance of stress depth to pitting depth and crack growth rates. For this project welded 316L stainless steel panels were configured to MPC geometry and laser peened in the same manner as deployed for actual canisters. Our two-dimensional stress mapping shows that high energy laser peening provides deep (>5 mm) plastic compression. Literature information is not clear as to specific dependence of crack initiation and growth rates on variables including temperature, specifics of chlorine exposure, pit nucleation and residual stress intensity and depth. In our CISCC testing, although extensive cracking developed quickly (less than 18 hours) in the unpeened area, no cracking developed at all in the laser peened sections after 340 hour exposure. We further show that cracking that initiated and grew in unpeened regions arrested upon propagating to the laser peened boundary. We performed detailed finite element stress analysis (FEA) to evaluate the difference in expected retention of stress generated by the peening of test panels and the more constrained geometry of actual storage canisters. Our analysis shows that the 4 mm depth of stress measured in unconstrained test panels correlates to actual stress depth in the confined canister geometry of 6 mm, that is approximately 2 mm deeper thus satisfying a key stress depth requirement. The accelerated CISCC tests indicate that MPC design life can be dramatically improved by laser peening thereby making the MPCs a viable technical and economic solution to prevent CISCC. Following qualification testing and system configuration, a high energy laser peening process was deployed to peen welds of the dry fuel canisters for the San Onofre Nuclear Power Plant. The laser peening thereby helps ensure that the storage canisters will remain free from chlorine induced stress corrosion cracking. Mul i-purpose canisters (MPCs) are being employed for dry canister storage of spent fuel at nuclear plant sites as a temporary approach until an interim or permanent dry storage site(s) is available. For storage in coastal or lakeside regions and even humid environment , the corrosive nature of the moist air with entrained chlo ides can make the w lded regions of the canisters susceptible to pitting and chloride induced stress corrosion cracking (CISCC). In this report we evaluate CISCC lif time of w lded 316L stainless steel caniste plat s showing in excess of 19 times i crease of laser peened panel s ctions vs. thos left as-welded using ASTM G36 (2013) accelerat corrosive te ti g. Specifically cracks ever developed or propagated into the laser pe ning area. We also provide measurements f residual stre s in tes plates and r lated calculations of stress ntensity and d p h exp ct in the full canister geometry. We discuss the r levance of stress depth to pitting depth and crack growth rates. For this proj ct welded 316L tainless steel panels were configured to MPC geometry laser peened in he ame manner as deploye for actual canisters. Our two-dimensional stress mapping shows that high energy laser peeni provides eep (>5 mm) pl stic c mpre sion. Literature informat on i not cle r a to spe ific dep ndence of crack initiation and growth rat s on vari bles including tempera re, specifics of chlorine exposure, pit nucleation and residual stress intensity and depth. In our CISCC testing, l hough extensive cracking developed quickly (less than 18 hours) in th unpeened area, no cr cking develop d at all in the laser peen d s ctions aft r 340 hour exposure. We further show that cracking that initiated and grew in unpee ed egions arrested upon propagati g to the laser p ened boundary. We performed detailed finite el m nt stress analysis (FEA) t evaluate the difference in xpected retention of stress generat d by the p ening of test panels and he more constrained geometry of actual storage canisters. Our analysis shows that the 4 mm depth of stress measured in unconstrained te t p nels correlates to actual stress d pth i the confin d canister geometry of 6 mm, t at is approximately 2 mm deep r thus satisfying a key str ss depth requirement. The accelerated CISCC test indicat that MPC design life can be dramatically improved by l s r peening thereby m king the MPCs a viable techni l and ec nomic solution to prevent CISCC. Following qualification testi and s em configuration, a high en rgy laser peening proces was deployed to peen welds of the dry fuel canisters for the San Onofr Nuclear Power Pla t. The laser peening hereby helps nsure that the storage canis ers will remain free from chlori e induced stre s corr sion cracking. © 2019 The Authors. Publ hed by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers. Fatigue Design 2019 Preventing Stress Corrosion Cracking of Spent Nuclear Fuel Dry Storage Canisters Lloyd Hackel (a) , Jon Rankin (a) , Matt Walter (a) , C Brent Dane (a) , William Neuman (b) , Pierre Fatigue Design 2019 Preventing Stress Corrosion Cracking of Spent Nuclear Fuel Dry St rage Ca isters Lloyd Hackel (a) , Jon Rankin (a) , Matt Walter (a) , C Brent Dane (a) , William Neuman (b) , Pierre Oneid (c) , Gareth Thom s (c) and Fred Bidrawn (c) a Curtiss-Wright Surface Technologies, b Intellifos, c Holtec International Corresponding author: Lloyd.Hackel@cwst.com Oneid (c) , Gareth Thomas (c) and Fred Bidrawn (c) a Curtiss-Wright Surface Technologies, b Intellifos, c Holtec International Corresponding author: Lloyd.Hackel@cwst.com Abstract Abstract

2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers. 2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers.

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