Rod internal pressure of spent nuclear fuel and its effects on cladding degradation during dry storage

Kim, Ju-Seong,Hong, Jong-Dae,Yang, Yong-Sik,Kook, Dong-Hak Elsevier 2017 JOURNAL OF NUCLEAR MATERIALS Vol.492 No.-

<P><B>Abstract</B></P> <P>Temperature and hoop stress limits have been used to prevent the gross rupture of spent nuclear fuel during dry storage. The stress due to rod internal pressure can induce cladding degradation such as creep, hydride reorientation, and delayed hydride cracking. Creep is a self-limiting phenomenon in a dry storage system; in contrast, hydride reorientation and delayed hydride cracking are potential degradation mechanisms activated at low temperatures when the cladding material is brittle. In this work, a conservative rod internal pressure and corresponding hoop stress were calculated using FRAPCON-4.0 fuel performance code. Based on the hoop stresses during storage, a study on the onset of hydride reorientation and delayed hydride cracking in spent nuclear fuel was conducted under the current storage guidelines. Hydride reorientation is hard to occur in most of the low burn-up fuel while some high burn-up fuel can experience hydride reorientation, but their effect may not be significant. On the other hand, delayed hydride cracking will not occur in spent nuclear fuel from pressurized water reactor; however, there is a lack of confirmatory data on threshold intensity factor for delayed hydride cracking and crack size distribution in the fuel.</P>

전자빔 용접 수소 균열 가능성 평가와 균열 방지를 위한 용접 조건 최적화

송지민(Jimin Song),이상훈(Sang hun Lee),박승환(Seunghwan Park),송명의(Myeongeui Song) 한국자동차공학회 2023 한국자동차공학회 학술대회 및 전시회 Vol.2023 No.11

A hydrogen-induced crack is referred to as a crack that occurs at temperatures blow approximately 100 oC after solidification in welding. The Hydrogen-induced crack initiation is caused by the combined effects of high brittleness of the weld, residual stress (maximum principal stress) and diffusible hydrogen in the weld. The cooling rate affects the content of diffusible hydrogen in weld. It is generally recognized that a high cooling rate causes a higher hydrogen content. In this study, FE analyses and tests in various welding conditions were performed. T8/5 cooling rate and residual stress results are extracted and plotted on the plane coordinate to estimate the possibility of the occurrence of the hydrogen-induced crack.

건조수축 균열저감을 위한 지연줄눈의 현장적용 및 계측

이명호(Lee Myung-Ho),소광호(Sho Kwang-Ho),박형철(Park Hyung-Cheol) 대한건축학회 2010 大韓建築學會論文集 : 構造系 Vol.26 No.8

Delay joints are useful to reduce shrinkage cracks to allow a significant part of the shrinkage to take without inducing stresses. Recently, delay joints have been used in slabs of underground parking lots. Mark Fintel proposed that delay joint is usually 60 to 90㎝ wide across the entire building. Development length of HD13 for longitudinal reinforcement of slab is about 60㎝, but, development length of HD25 for longitudinal reinforcement of beam is about 220㎝. So, different development lengths between slab and beam make difficult to construct the delay joint. In this paper delay joints are constructed to have same width in slab and beam regions uncutting reinforcements in beam region. Also, to confirm the possibility to construct delay joint uncutting the longitudinal reinforcement of beam, behavior of restrained beam reinforcement in regions of delay joint was monitored using total eighteen measuring instruments (strain gauges, LVDTs, thermo couple and so on). Lastly effect of delay joint was investigated through the assessment of occurred slab crack.

지연줄눈 구간의 구속된 보 및 슬래브 철근의 거동

이명호(Lee Myung-Ho),박형철(Park Hyung-Cheol),오보환(Oh Bo-Hwan) 대한건축학회 2009 大韓建築學會論文集 : 構造系 Vol.25 No.12

Delay joints are temporary joints that are left open for a certain time during construction to allow a significant part of the shrinkage to take without inducing stresses. Recently, delay joints have been used to a considerable extent in slabs of underground parking lots, for the purpose of reducing shrinkage stresses and minimizing shrinkage cracks. Mark Fintel proposed that delay joint is usually 60 to 90㎝ wide across the entire building. Development length of HD13 for longitudinal reinforcement of slab is about 60㎝, but, development length of HD25 for longitudinal reinforcement of beam is over 200㎝. So, different development lengths between slab and beam make difficult to construct the delay joint. In this paper delay joints are constructed to have same width in slab and beam regions uncutting reinforcements in beam region. Also, behavior of restrained beam and slab reinforcement in regions of delay joint was evaluated.

시편 예열 온도가 FCW 용착금속의 확산성 수소량에 미치는 영향

김동윤,황인성,김동철,강문진,Kim, Dong Yoon,Hwang, In Sung,Kim, Dong Cheol,Kang, Moon Jin 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.2

Cold cracking of weldment is one of the most serious welding problems. A sufficient quantity of diffusible hydrogen, a residual stress, and a sensitive microstructure are the causes of cold cracking. Removal of any one of these factors can be used to prevent cold cracking. Application of flux cored arc welding process is increasing due to high productivity and easiness of welding. In addition, to prevent cold cracking in the HAZ or weldment, preheat temperature and interpass temperature have to be controlled. In this study, the effect of preheat temperature on the levels of diffusible hydrogen in the weld metal deposited using flux cored wire was examined. The levels of preheat temperature of base metal specimen were ambient temperature, 50, 100 and $150^{\circ}C$ respectively. The result showed that the increase of preheat temperature was a linear relationship with reduction of diffusible hydrogen content in weldment.

대구경-후판 압력용기용 저 합금강(Mn-Mo)의 용접특성

안종석,박진근,윤재연,Ahn, Jong-Seok,Park, Jin-Keun,Yoon, Jae-Yeon 대한용접접합학회 2012 대한용접·접합학회지 Vol.30 No.6

Recently the low alloy steel plate made with manganese-molybdenum is used widely in steam drum and separator of the new coal-fired power plant boiler. This material is suitable for the vapor storage of high pressure and high temperature. The high temperature creep strength of Mn-Mo alloy is higher than the carbon plate(SA516) that used in the subcritical pressure boiler. It reduces the thickness of the pressure vessel and makes the lightweight possible. Recently in the power plant boiler operation and production process, the damage has happened frequently in the heat affected zone and base material according to the hydrogen crack and delayed crack. This paper describes the research result about the damage case experienced in the boiler steam drum production process and present the optimum manufacture method for the similar damage prevention of recurrence.

Effect of Hydride Reorientation on Delayed Hydride Cracking In Zr-2.5Nb Tubes

Yun Yeo Bum,Kim Young Suk,Im Kyung Soo,Cheong Yong Moo,Kim Sung Soo Korean Nuclear Society 2003 Nuclear Engineering and Technology Vol.35 No.6

The objective of this study is to investigate the reorientation of hydrides with applied stress intensity factor, the peak temperature and the time when to apply the stress intensity factor in a Zr-2.5Nb pressure tube during its thermal cycle treatment. Cantilever beam (CB) specimens with a notch of 0.5 mm in depth made from the Zr-2.5Nb tube were subjected to electrolytic hydrogen charging to contain 60 ppm H and then to a thermal cycle involving heating to the peak temperature of either 310 or $380^{\circ}C$, holding there for 50 h and then cooling to the test temperature of $250^{\circ}C$. The stress intensity factor of either 6.13 or $18.4\;MPa\sqrt{m}$ was applied at the beginning of the thermal cycle, at the end of the hold at the peak temperatures and after cooling to the test temperature, respectively. The reorientation of hydrides in the Zr-2.5Nb tube was enhanced with the increased peak temperature and applied stress intensity factor. Furthermore, when the CB specimens were subjected to $18.4\;MPa\sqrt{m}$ from the beginning of the thermal cycle, the reoriented hydrides occurred almost all over the Zr-2.5Nb tube, surprisingly suppressing the growth of a DHC crack. In contrast, when the CB specimens were subjected to the stress intensity factor at the test temperature, little reorientation of hydrides was observed except the notch region, leading the Zr-2.5Nb to grow a large DHC crack. Based on the correlation between the reorientation of hydrides and the DHC crack growth, a governing factor for DHC is discussed along with the feasibility of the Kim's DHC model.

Theoretical models of threshold stress intensity factor and critical hydride length for delayed hydride cracking considering thermal stresses

Jingyu Zhang,Jiacheng Zhu,Shurong Ding,Liang Chen,Wenjie Li,Hua Pang 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.7

Delayed hydride cracking (DHC) is an important failure mechanism for Zircaloy tubes in the demandingenvironment of nuclear reactors. The threshold stress intensity factor, KIH, and critical hydride length, lC ,are important parameters to evaluate DHC. Theoretical models of them are developed for Zircaloy tubesundergoing non-homogenous temperature loading, with new stress distributions ahead of the crack tipand thermal stresses involved. A new stress distribution in the plastic zone ahead of the crack tip isproposed according to the fracture mechanics theory of second-order estimate of plastic zone size. Thedeveloped models with fewer fitting parameters are validated with the experimental results for KIH andlC. The research results for radial cracking cases indicate that a better agreement for KIH can be achieved;the negative axial thermal stresses can lessen KIH and enlarge the critical hydride length, so its effectshould be considered in the safety evaluation and constraint design for fuel rods; the critical hydridelength lC changes slightly in a certain range of stress intensity factors, which interprets the phenomenonthat the DHC velocity varies slowly in the steady crack growth stage. Besides, the sensitivity analysis ofmodel parameters demonstrates that an increase in yield strength of zircaloy will result in a decrease inthe critical hydride length lC , and KIH will firstly decrease and then have a trend to increase with the yieldstrength of Zircaloy; higher fracture strength of hydrided zircaloy will lead to very high values ofthreshold stress intensity factor and critical hydride length at higher temperatures, which might be themain mechanism of crack arrest for some Zircaloy materials

합금속의 수소취성과 응력부식균열 고찰

김영석,임경수,정용무 한국수소및신에너지학회 2004 한국수소 및 신에너지학회논문집 Vol.15 No.4

The objective of this study is an understanding of stress corrosion cracking of metals that is recognized to mostly limit the lifetime of the structural materials by comparing the features of delayed hydride cracking of zirconium alloys with those of stress corrosion cracking (SCC) of Ni-based alloys and hydrogen cracking of stainless steels. To this end, we investigated a dependence of delayed hydride cracking (DHC) velocity on the applied stress intensity factor and yield strength, and correlated a temperature dependence of the striation spacing and the DHC velocity. We reviewed a similarity of the features between the DHC of zirconium alloys, the SCC of Ni-based alloys and turbine rotor steels, and the hydrogen cracking of stainless steels and discussed the SCC phenomenon in metals with our DHC mode

Mechanism of crack propagation for K9 glass

Xiaoguang Guo,Yutong Shi,Xichun Luo,Renke Kang,Zhuji Jin,Fei Ding,Zhipeng Li 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.5

In order to study the mechanism of crack propagation, the varied cutting-depth scratch experiment is carried out and smoothed particle hydrodynamics (SPH) simulation method is used to assistant the investigation. The SPH simulation results reveal that crack will propagate in the direction where stress concentration exceeds the fracture toughness of K9 glass. The initial crack length in critical transition depth is calculated by combining the critical stress of fracture and the fracture toughness of K9 glass. Based on the effective plastic strain, the relation between scratching depth and crack depth is obtained. The recovery of crack tip is found and explained from the relationship between cutting depth and crack depth. Using the energy balance theory of Griffith, the variation of material internal energy is revealed. Comparing the scratching forces obtained from experiment and simulation, the validity of simulation results is verified. The phenomenon of crack delayed propagation is found in both experiment and simulation. The explanation of mechanism is given.