In nuclear fuel development research, consideration of the back-end cycle is essential. In particular, a review of an in-reactor performance of nuclear fuel related to the various degradation phenomena that can occur during spent fuel dry storage is an important area. The important factors affecting the degradation of zirconium-based cladding during dry storage are the cladding’s hydrogen concentration and rod internal pressure after irradiation. In this study, a preliminary analysis of the in-reactor behavior of the HANA cladding, which has been developed and is currently undergoing licensing review, was performed, and based on this result, a comparative analysis between nuclear fuel with HANA cladding and current commercial fuel under storage conditions was performed. The results show that the rod internal pressure of nuclear fuel with HANA cladding is not significantly different from that of commercial cladding, and the hydrogen concentration in the cladding tends to reduce due to the increased corrosion resistance, so fuel integrity in a dry storage conditions is not expected to be a major problem. Although the lack of cladding creep data under dry storage conditions, the results from the Halden research reactor test comparing in-reactor creep behavior with Zircaloy-4 showed that there is sufficient margin for degradation due to creep during storage.

Cathepsins (CTSs), a family of lysosomal cysteine proteases, and their inhibitors (CSTs) play a critical role in remodeling of the uterine endometrium and placenta for the establishment and maintenance of pregnancy in many animal species including rodents, sheep, cow and pigs. It has been shown that the high rate of pregnancy failure by somatic cell nuclear transfer (SCNT) is associated with abnormal placental development. Our previous study has shown that CST6 is highly expressed in the uterine endometrium from mid to late pregnancy in pigs. In this study, to understand whether appropriate endometrial and placental tissue remodeling occurs in the uterine endometrium from gilts with conceptuses derived from SCNT during pregnancy in pigs, we investigated expression of CST6 in the uterine endometrium. Uterine endometrial tissues were obtained from gilts that carried SCNT-derived normal conceptuses (NT-No) and abnormal conceptuses (NT-Ab), and from gilts carrying conceptuses from natural mating (Non-NT) on D114 of pregnancy. Immunoblot analysis showed that CST6 protein levels in the endometrial tissues of gilts carrying NT-No were lower than those of gilts carrying Non-NT. The levels of CST6 protein in the endometrial tissues of gilts carrying NT-Ab decreased even more than those of gilts carrying NT-No. These results indicate that decreased expression of CST6 in the endometrium with NT-No and NT-Ab reflects inappropriate endometrial tissue remodeling and pregnancy failure of pigs with SCNT derived conceptuses and that CST6 plays an important role for the maintenance of pregnancy in pigs. * This work was supported by the Next Generation BioGreen 21 program (#PJ007997), RDA, Republic of Korea.

Proteases and their inhibitors are involved in the process of pregnancy by remodeling uterine endometrium and placenta in many mammals. During placentation, proteases and their inhibitors contribute to formation of epitheliochorial type placentation in pigs. Our previous study showed that LGMN and CST6 were expressed in the uterine endometrium and localized mainly to glandular epithelial cells (GE) and chorionic membrane (CM) during mid to late pregnancy. In this study, we investigated expression of LGMN and CST6 in the uterine endometrium and fetal membrane during pregnancy in pigs. Uterine endometrial tissue samples and fetal membrane samples were collected from D30, D60, D90, and D114 of pregnancy. Real-time RT-PCR analysis showed that both LGMN and CST6 mRNAs were detected in the uterine endometrium and fetal membrane in all samples with higher levels during mid to late stage of pregnancy. Analysis by immunoblotting revealed that LGMN protein was present in the porcine uterine endometrium and fetal membrane. Based on the placental and endometrial distribution of proteases and their inhibitors, we examined LGMN mRNA and LGMN protein expression in the neonatal pigs. In situ hybridization analysis using the intestine from D90 of piglet revealed that LGMN mRNA was highly expressed in the absorptive epithelium of the intestinal villi. Immunohistochemical experiments demonstrated that LGMN protein was localized to epithelial villi. These results suggest a possible role of LGMN in modification of proteins that are transported through the fetal membrane from the uterine for successful transport and utilization in the fetus.