Study on water stopping, repair and stabilization of lower PCV by geopolymer, etc. (Contract research); FY2022 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; The University of Tokyo*

JAEA-Review 2024-021, 126 Pages, 2024/11

JAEA-Review-2024-021.pdf:6.51MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2022. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2021, this report summarizes the research results of the "Study on water stopping, repair and stabilization of lower PCV by geopolymer, etc" conducted in FY2022. The present study aims to propose a construction method to stop jet deflectors by improved geopolymer and ultra-heavy muddy water, and to repair the lower part of the dry well. In addition, in order to increase the options for on-site construction in unknown situations such as deposition conditions, we will examine a wide range of construction outside the pedestal, and evaluate the feasibility of the construction method by the latest thermal flow simulation method.

Implication of E3 ligase RAD18 in UV-induced mutagenesis in human induced pluripotent stem cells and neuronal progenitor cells

Shimada, Mikio*; Tokumiya, Takumi*; Miyake, Tomoko*; Tsukada, Kaima*; Kanzaki, Norie; Yanagihara, Hiromi*; Kobayashi, Junya*; Matsumoto, Yoshihisa*

Journal of Radiation Research (Internet), 64(2), p.345 - 351, 2023/03

https://doi.org/10.1093/jrr/rrac099

Replacement of upper core structure in experimental fast reactor Joyo, 1; Existing damaged upper core structure jack-up test

Ito, Hiromichi; Suzuki, Nobuhiro; Kobayashi, Tetsuhiko; Kawahara, Hirotaka; Nagai, Akinori; Sakao, Ryuta*; Murata, Chotaro*; Tanaka, Junya*; Matsusaka, Yasunori*; Tatsuno, Takahiro*

Proceedings of 2015 International Congress on Advances in Nuclear Power Plants (ICAPP 2015) (CD-ROM), p.1058 - 1067, 2015/05

In the experimental fast reactor Joyo (Sodium-cooled Fast Reactor (SFR)), it was confirmed that the top of the irradiation test sub-assembly had bent onto the in-vessel storage rack as an obstacle and had damaged the upper core structure (UCS). There is a risk of deformation of the UCS and guide sleeve (GS) caused by interference between them unless inclination is controlled precisely. To mitigate the risk, special jack-up equipment for applying three-point suspension was developed. The existing damaged UCS (ed-UCS) jack-up test using the jack-up equipment was conducted on May 7, 2014. As a result of this test, it was confirmed that the ed-UCS could be successfully jacked-up to 1000 mm without consequent overload. The experience and knowledge gained in the ed-UCS jack-up test provides valuable insights and prospects not only for UCS replacement but also for further improving and verifying repair techniques in SFRs.

Studies on maintainability and repairability for Japan Sodium-cooled Fast Reactor (JSFR)

Isono, Kenichi; Kubo, Shigenobu; Chikazawa, Yoshitaka; Dozaki, Koji*; Oya, Takeaki*; Yui, Masahiro*

Proceedings of 22nd International Conference on Nuclear Engineering (ICONE-22) (DVD-ROM), 7 Pages, 2014/07

https://doi.org/10.1115/ICONE22-30175

Aiming at enabling maintenance and repair of almost all components in JSFR demonstration reactor to a level equivalent to that attained for the light water reactors, we identified a number of parts which have difficulty in maintenance and repair in main components of the reactor structure and the primary/secondary main coolant system. And we defined the criteria for design improvement and then provided candidates of improvement measures for the identified parts. Furthermore, we made a modification of the plant design in a consistent manner integrating the improvements investigated for each major component. A series of evaluations were conducted to check the feasibility as a power plant. As the result, we found that the concept could be adopted not only to the demonstration reactor (750 MWe) but to the commercial one (1500 MWe).

Enzymatic recognition of radiation-produced oxidative DNA lesion; Molecular dynamics approach

Pinak, M.

Modern Methods for Theoretical Physical Chemistry of Biopolymers, p.191 - 210, 2006/00

Results of molecular dynamics (MD) studies of several lesions on DNA and their respective repair enzymes are presented. Main focus is to describe structural and energy changes in DNA molecule with the respect to proper recognition of the lesion by respective repair enzyme. Pyrimidine and purine lesions were studied using MD simulation code Amber and respective force field modified for each lesion. The significant structural changes as breaking of hydrogen bonds network opening and bending the DNA double helix were observed. This collapsing of the double helical structure around the lesion is considered to facilitate docking of the repair enzyme into the DNA. Specific values of electrostatic interaction energy that enables repair enzyme to discriminate lesion from non-damaged site were also detected at several lesion sites.

Theoretical study of the human DNA repair protein HOGG1 activity

Schyman, P.*; Danielsson, J.*; Pinak, M.; Laaksonen, A.*

Journal of Physical Chemistry A, 109(8), p.1713 - 1719, 2005/02

https://doi.org/10.1021/jp045686m

We have examined the role of the catalytic lysine (Lys 249) in breaking the glycosidic bond of 8-oxoguanine in the enzyme human 8-oxoguanine DNA glycosylase. It has been assumed that this lysine acts as a nucleophile in a S2 type of reaction after being activated through a donation of a proton to a strictly conserved aspartate. We use hybrid density functional theory to characterize both associative and dissociative pathways. We find that the smallest energetical barrier involves a S1 type of mechanism where the lysine electrostatically stabilizes the dissociating base and then donates a proton with a very small barrier and then finally attacks the sugar ring to create the covalently bounded protein-DNA intermediate complex. Reported findings give further support to the assumption that a dissociative mechanism may be the preferred mode of action for this type of enzymes.

Impact of radiation damage on DNA determined by computational simulation

Pinak, M.

Hoken Butsuri, 39(1), p.35 - 41, 2004/03

https://doi.org/10.5453/jhps.39.35

Review of molecular dynamics (MD) studies of several radiation-originated lesions on DNA molecules is presented. Main focus is to describe structural and energy changes in DNA molecule with the respect to proper recognition of the lesion by respective repair enzyme. In most cases the observed changes are related to overall collapsing of the double helical structure around the lesion and are considered to facilitate docking of the repair enzyme into the DNA and formation of DNA-enzyme complex. Stable DNA-enzyme complex is necessary condition for the onset of entire enzymatic repair process. In addition to the structural changes, specific values of electrostatic interaction energy are detected at several lesion sites. The specific electrostatic energy is considered as a factor that enables repair enzyme to discriminate lesion from native, non-damaged site.

Computational determination of radiation damage effects on DNA structure

Pinak, M.

Central European Journal of Physics, 1(1), p.179 - 190, 2003/01

The molecular dynamics (MD) studies of several radiation originated lesions on the DNA molecules are presented with the respect to the proper recognition of the lesion by the respective repair enzyme. Several pyrimidine and purine lesions were subjected to the MD simulations for several hundreds picoseconds using MD simulation code AMBER 5.0 and respective force field modified for the lesion. In all cases the significant structural changes in the DNA double helical structure were observed. These changes were related to the overall collapsing double helical structure around the lesion and are supposed to facilitate the docking of the repair enzyme into the DNA in formation of DNA-enzyme complex. In addition to the structural changes, the specific values of electrostatic interaction energy were found at several lesion sites.

Disruption tests on repaired tungsten by CVD coating

Taniguchi, Masaki; Sato, Kazuyoshi; Ezato, Koichiro; Yokoyama, Kenji; Akiba, Masato

Journal of Nuclear Materials, 307-311(Part1), p.719 - 722, 2002/12

https://doi.org/10.1016/S0022-3115(02)01041-3

no abstracts in English

Characterization of RecA424 and RecA670 proteins from

Sato, Katsuya; Narumi, Issei; Kikuchi, Masahiro; Kitayama, Shigeru; Yanagisawa, Tadashi*; Yamamoto, Kazuo; Watanabe, Hiroshi

Journal of Biochemistry, 131(1), p.121 - 129, 2002/01

https://doi.org/10.1093/oxfordjournals.jbchem.a003066

RecA protein is considered to be the most important participant in the radiation resistance of . We identified a new mutation () in the DNA-repair deficient mutant strain KI696, the phenotype of which is remarkably different from mutant strain rec30 carrying . In vitro, neither RecA424 nor RecA670 could promote DNA strand exchange, indicating that both RecA424 and Rec670 are defective in recombination activity. RecA424 promoted the autocleavage reaction of LexA in vitro, whereas RecA670 did not. The LexA level in KI696 was decreased following -irradiation. However, the LexA level in strain rec30 was constant irrespective of irradiation. These results indicate that RecA424 retains co-protease activity, whereas RecA670 does not. While strain rec30 is extremely radiation sensitive, strain KI696 is only slightly sensitive. Together, these observations suggest that the co-protease activity rather than the recombination activity of RecA contributes to the radiation resistance in .