Cold Spray Deposition Coatings to Extend Lifetime of Spent Nuclear Fuel Storage Stainless Steel Canisters

Hwasung Yeom,Kumar Sridhran 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1

Long-term safe storage of spent nuclear fuel (SNF) determines sustainability of the current light water reactor (LWR) fleet. In the U.S., SNF is stored in stainless steel canister in dry cask storage system (DCSS) after spending several years in wet pool storage system while there is no DSCC in Republic of Korea. The SNF storage time in DSCC is expected to be multiple decades since no permanent geological repositories are identified in both countries. One limiting factor for extended storage of SNF in DSCC is chloride-induced stress corrosion cracking (CISCC) in the welded regions of the stainless steel canisters. The propensity for the occurrence of CISCC has warranted the development of the mitigation and repair technologies to ensure the safe and long-term storage for both present and new canister although no CISCC failure was reported yet. This study investigates cold spray deposition coatings of 304 L and 316 L stainless steels on prototypical stainless steel canisters such as sensitized flat and C-ring samples. The cold spray technology has been identified as the most promising approach by Extended Storage Collaboration Program (ESCP) driven by Electric Power Research Institute (EPRI). The talk includes microstructural characterization, adhesion strength measurement, residual stress evaluation, and corrosion behavior of the coated materials in boiling MgCl2 solution and electrochemical corrosion tests in NaCl solution. In addition, the capability of repair of cracks on the canister surface using the coating technology will be presented.

Technical Aspects of Back-end Fuel Cycle of Advanced Accident Tolerant Fuel

Hwasung Yeom,Kumar Sridharan 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2

The Fukushima-Daiichi accident in 2011 revealed the limitations of Zr-alloys in accident scenarios where severe steam oxidation led to the liberation of heat and hydrogen and the destruction of the reactor core. In response to this accident, there has been a concerted effort by industry, national laboratories, and universities to develop cladding and fuel materials for lightwater reactors (LWRs) that are more accident tolerant. The near-term approach has been to develop coatings for Zr-alloys that would provide additional safety and operational margin by virtue of its excellent corrosion/oxidation resistance at both normal and accident conditions. The designs being considered for implementation by major nuclear fuel suppliers include a thin Cr or a ceramic coating on the conventional LWR fuel cladding. For improved economics, the industries are also considering ATF coated cladding with high enrichment fuel (up to 8%) to achieve high burnup (> 75 GWd/MTU). While the development of ATF concepts (i.e., the front end of the fuel cycle), including coated claddings and doped fuels have progressed at an accelerated pace, relatively less attention has been devoted to the used fuel disposition of ATF fuels (i.e., the backend of the fuel cycle). For accelerated deployment of the ATF designs in the current LWR fleet, it is necessary to investigate technical aspects of the ATF used nuclear fuel (UNF) management in transportation, storage, and disposal. This presentation will provide a brief overview of state-of-the-art ATF developments and list out potential considerations to apply the fuels into back-end fuel cycle. New test plan should be planned to compare the characteristics of current LWR used nuclear fuels with those of the new fuel designs. For example, research focus can be understanding of ATF used fuel particulate size and quantity (at high burnup condition) and mechanical integrity of coated cladding under normal and off-normal conditions during transportation and long-term storage. Finally, the impacts of CRUD on the new fuel cladding, increased container weight, temperature, and radiation level to the back-end fuel cycle activities need to be investigated.

Surface Engineering Technologies for Mitigation and Repair of Chloride- Induced Stress Corrosion Cracking in Stainless-Steel Canisters for Spent

Jinwook Choi,Hwasung Yeom 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2

Safe management of spent nuclear fuel (SNF) is a key issue to determine sustainability of current light water reactor (LWR) fleet. However, none of the countries are actually conducting permanent disposal of SNFs yet. Instead, most countries are pursuing interim storage of spent nuclear fuels in dry cask storage system (DCSS). These dry casks are usually made of stainlesssteels for resistibility against cracking and corrosion, which can be occurred over a long-term storage period. Nevertheless, some corrosion called Chloride-Induced Stress Corrosion Cracking (CISCC) can arise in certain conditions, exacerbating the lifetime of dry casks. CISCC can occur if the three conditions are satisfied simultaneously: (i) residual tensile stress, (ii) material sensitization, and (iii) chloride-rich environment. A residual tensile stress is developed by the two processes. One is the bending process of stainless-steel plates into a cylindrical shape, and the other is the welding process, which can incur solidification-induced stress. These stresses provide a driving force of pit-to-crack transition. Around the fusion weld areas, chromium is precipitated at the grain boundary as a carbide form while it depletes chromium around it, leading to material susceptible to pitting corrosion. It is called sensitization. Finally, coastal regions, where nuclear power plants usually operate, tend to have a higher relative humidity and more chloride concentration compared to inland areas. This high humidity and chloride ion concentration initiate pitting corrosion on the surface of stainless-steels. To prevent initiation of CISCC, at least one of the three conditions should be removed. For this, several surface engineering techniques are under investigation. One of the most promising approaches is surface peening method, which is the process that impacts the surface of materials with media (e.g., small pins, balls, laser pulse). By this impact, plastic deformation on the surface occurs with compressive stress that counteracts with pre-existing residual tensile stress, so this approach can prevent pit-to-crack transition of stainless-steels. Also, cold spray deposition can prevent CISCC. Cold spray deposition is a method of spraying fine metal powder to a substrate by accelerating them to supersonic velocity with propellant gas. As a result, a thin coating composed of the feedstock powders can protect the substrate from outer corrosive environments. In addition, the impact of the feedstock powder on the substrate during the process provides compressive stress, similar to the peening method.

Evaluation of critical heat flux of ATF candidate coating materials in pool boiling

Jo, HangJin,Yeom, Hwasung,Gutierrez, Emilio,Sridharan, Kumar,Corradini, Michael North-Holland Pub. Co 2019 Nuclear engineering and design Vol.354 No.-

<P><B>Abstract</B></P> <P>The critical heat flux (CHF) of potential accident tolerant fuel (ATF) cladding materials and concepts, Cr and FeCrAl coatings on zirconium-alloy substrates, was investigated experimentally. A cold spray process, which involves the propulsion of high velocity powder particles on to the substrate surface to form a coating upon impact, was used to create the coatings. Surface parameters such as contact angle, surface roughness, and morphology that are associated with CHF in pool boiling were characterized. Non-hydrodynamic effects of newly developed ATF candidate coating materials on CHF were also evaluated. The effects of thermal properties and coating thickness and expected challenges for evaluation of CHF for new ATF cladding materials development are discussed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Evaluating critical heat flux (CHF) on accident tolerant fuel cladding designs. </LI> <LI> Analyzing CHF with surface characteristics. </LI> <LI> Discussing non-hydrodynamic effects on CHF for nuclear cladding designs. </LI> </UL> </P>

Mobile-IP 환경에서 캐쉬 버퍼를 이용한 신뢰적인 멀티캐스트 데이터 전송방법

염홍주(Hongju Yeom),김화성(Hwasung Kim) 한국통신학회 2004 한국통신학회 학술대회논문집 Vol.2004 No.7

Mobile-IP환경에서 데이터 손실 방지를 위한 효과적인 멀티캐스트 메커니즘

염홍주(Hongju Yeom),이상호(Sangho Lee),김영진(Youngjin Kim),김화성(Hwasung Kim) 한국통신학회 2004 한국통신학회 학술대회논문집 Vol.2004 No.11

IP기반 이동통신 시스템에서 데이터 손실방지를 위한 효과적인 멀티캐스트 메커니즘

염홍주(Hongju Yeom),김화성(Hwasung Kim) 한국통신학회 2005 한국통신학회 학술대회논문집 Vol.2005 No.6

A Novel Approach for Manufacturing Oxide Dispersion Strengthened (ODS) Steel Cladding Tubes using Cold Spray Technology

Benjamin Maier,Mia Lenling,Hwasung Yeom,Greg Johnson,Stuart Maloy,Kumar Sridharan 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.4

A novel fabrication method of oxide dispersion strengthened (ODS) steel cladding tubes for advanced fastreactors has been investigated using the cold spray powder-based materials deposition process. Coldspraying has the potential advantage for rapidly fabricating ODS cladding tubes in comparison with theconventional multi-step extrusion process. A gas atomized spherical 14YWT (Fe-14%Cr, 3%W, 0.4%Ti, 0.2%Y, 0.01%O) powder was sprayed on a rotating cylindrical 6061-T6 aluminum mandrel using nitrogen asthe propellant gas. The powder lacked the oxygen content needed to precipitate the nanoclusters in ODSsteel, therefore this work was intended to serve as a proof-of-concept study to demonstrate that freestandingsteel cladding tubes with prototypical ODS composition could be manufactured using thecold spray process. The spray process produced an approximately 1-mm thick, dense 14YWT deposit onthe aluminum-alloy tube. After surface polishing of the 14YWT deposit to obtain desired claddingthickness and surface roughness, the aluminum-alloy mandrel was dissolved in an alkaline medium toleave behind a free-standing ODS tube. The as-fabricated cladding tube was annealed at 1000 C for 1 hin an argon atmosphere to improve the overall mechanical properties of the cladding