During a severe accident, hydrogen distribution and the depletion characteristics of passive autocatalytic recombiners (PARs) are highly dependent on containment thermal-hydraulic behavior. While pressure control systems—such as sprays, reactor containment fan-coolers (RCFC), filtered containment venting systems (FCVS), and passive containment cooling systems (PCCS)—are essential for maintaining containment integrity, their operation may influence the effectiveness of hydrogen mitigation strategies. This study experimentally evaluates PAR hydrogen removal characteristics under the operating conditions of RCFC and PCCS. Results indicate that during PAR-PCCS integrated operation, hydrogen removal rates remained consistent with established correlations, suggesting that PCCS operation has a negligible impact on PAR performance. Furthermore, experimental evaluations under fan-cooler operation demonstrate that forced convection induced by the fan-cooler does not negatively affect the hydrogen removal capability of the PAR installed above the fan-cooler. These findings confirm that the combined operation of pressure control systems and PARs maintains hydrogen safety, offering experimental validation for integrated containment management strategies during severe accidents.

Natural killer (NK) cells play a crucial role in immune surveillance by recognizing and eliminating tumor cells. However, tumors employ various mechanisms to evade NK cell-mediated immunity. NKp30 is a potent activating receptor on NK cells, but its function can be inhibited by specific ligands secreted by cancer cells. Here, we identified dipeptidase 1 (DPEP1) as a novel ligand for NKp30 in KM12C colon cancer cells, using co-immunoprecipitation, confocal microscopy, and flow cytometry. We examined how the DPEP1-NKp30 interaction affects NK cell activity and found that NK cytotoxicity increased in KM12C cells with DPEP1 knockdown but was significantly reduced in HCT116 cells overexpressing DPEP1. We further demonstrated that DPEP1 is secreted via extracellular vesicles and that its interaction with NKp30 suppressed the expression and secretion of perforin 1, granzyme B, CD107a, and interferon-γ in NK92 cells. In a xenograft mouse model treated with NK92 cells, tumors derived from HCT116/DPEP1 cells were significantly larger than those from HCT116/mock cells. Using peripheral blood-derived human NK cells, we confirmed that DPEP1 inhibited both cytotoxicity and granzyme B secretion. These findings suggest that disrupting the DPEP1-NKp30 interaction may enhance NK cell-mediated cytotoxicity and represent a novel therapeutic strategy for cancer immunotherapy.

In a pressurized water reactor (PWR) during a loss of coolant accident (LOCA) or a station blackout (SBO) accident, water and steam are released into the containment building. The water vapor mixes with the atmosphere, partially condensing into droplets or condensing on the containment walls. Although a significant amount of water vapor condenses, it coexists with hydrogen generated by the reactor core oxidation. As water vapor condenses, the volume fraction of hydrogen increases, raising the risk of explosion or flame acceleration. As such, water vapor’s behavior directly affects hydrogen distribution. To conservatively evaluate hydrogen safety in a PWR during a severe accident, lumped-parameter codes have been heavily used. As a best-estimate approach for hydrogen safety analysis in a PWR containment, a turbulence-resolved CFD code called contain3D has been developed. This paper presents the validation results of the code and simulation results of hydrogen behavior affected by water vapor condensation and hydrogen removal by passive autocatalytic recombiners (PARs) in the APR1400 containment. The results provide insight into the three-dimensional behaviors of the hydrogen in the containment.

Paulownin, a natural compound derived from Paulownia tomentosa wood, exhibits various physiological functions, including anti-bacterial and anti-fungal effects. However, the impact of paulownin on natural killer (NK) cell immune activity remains largely unknown. In this study, we investigated the effect of paulownin on NK cell activity both in vitro and in vivo, and explored its potential mechanisms. NK-92 cells were used for in vitro experiments and a BALB/c mouse model with B16F10 cells injected subcutaneously were used for in vivo anti-tumor analysis. We found that paulownin enhanced the cytolytic activity of NK-92 cells against leukemia, human colon, and human lung cancer cell lines. Paulownin treatment increased the expression of the degranulation marker protein CD107a and cytolytic granules, including granzyme B and perforin in NK-92 cells. Moreover, these enhancements of cytotoxicity and the expression of cytolytic granules induced by paulownin were also observed in human primary NK cells. Signaling studies showed that paulownin promoted the phosphorylation of JNK. The increased perforin expression and elevated cytotoxic activity induced by paulownin were effectively inhibited by pre-treatment with a JNK inhibitor. In vivo studies demonstrated that the administration of paulownin suppressed the growth of B16F10 melanoma cells allografted into mice. Paulownin administration promoted the activation of NK cells in the spleen of mice, resulting in enhanced cytotoxicity against YAC-1 cells. Moreover, the anti-tumor effects of paulownin were reduced upon the depletion of NK cells. Therefore, these results suggest that paulownin enhances NK cell cytotoxicity by activating the JNK signaling pathway and provide significant implications for developing new strategies for cancer immunotherapy.

In the present study, we investigated the velocity distribution, temperature distribution and condensation characteristics of steam jet issuing from four different orifice nozzles with a Reynolds number of approximately 79,000 using the phase Doppler particle analyzer system and a K-type thermocouple. The steam jet discharged from the orifice nozzle has a wider jet width compared to pipe nozzle because of the vena-contracta which can enhance the mixing of steam jet with the ambient air. Therefore, the orifice jet showed less condensation due to its wideness, resulting in small velocity decay rate and large temperature decay rate due to momentum conservation and decreased latent heat release compared to pipe nozzle, respectively. Also, the wider jet width of the orifice jet resulted in larger velocity and temperature spread rate compared to the pipe jet. In addition, the increase in the aspect ratio of the orifice jet led to more condensation and larger velocity spread rate and temperature spread rate due to both the vena-contracta and axis-switching effect, resulting in the increase of jet entrainment.

Rho guanine nucleotide dissociation inhibitor 1 (RhoGDI1) plays a critical role in regulating the activity of Rho guanosine triphosphatases (GTPases). Phosphorylation of RhoGDI1 dynamically modulates the activation of Rho GTPases, influencing cell proliferation and migration. This study explored the involvement of Never In Mitosis A (NIMA)-related serine/threonine protein kinase 2 (NEK2) in phosphorylating RhoGDI1 and its implications in cancer cell behavior associated with tumor progression. We employed GST pull-down assays and immunoprecipitation to investigate the interaction between NEK2 and RhoGDI1. Truncation fragments identified the region of RhoGDI1 responsible for binding with NEK2. Phosphorylation assays determined the site of NEK2-mediated phosphorylation on RhoGDI1. Functional assays were conducted using overexpression of the RhoGDI1 substitution mutant to assess their impact on cancer cell behavior. NEK2 directly bound to RhoGDI1 and phosphorylated it at Ser174. This phosphorylation event facilitated cancer cell proliferation and motility by activating RhoA and Rac1. The RhoGDI1 aa 112-134 region was critical for the binding to NEK2. Disruption of the NEK2-RhoGDI1 interaction through overexpression of a RhoGDI1 truncated fragment (aa 112-134) led to diminished RhoGDI1 phosphorylation and RhoA/Rac1 activation induced by NEK2, resulting in reduced cancer cell proliferation and migration. Moreover, in vivo studies showed reduced tumor growth and lung metastasis when the NEK2-RhoGDI1 interaction was disrupted. This study indicates that NEK2 promotes the metastatic behaviors of cancer cells by activating RhoA and Rac1 by phosphorylating RhoGDI1.

Passive auto-catalytic recombiners (PARs) are widely used to mitigate a hydrogen hazard. The first step to evaluate the hydrogen safety by PARs is to obtain qualified test data of the PARs for validation of their analytical model. SPARC PAR tests SP8 and SP9 were conducted to evaluate the hydrogen recombination characteristics of a honeycomb-shaped catalyst PAR. To obtain the hydrogen recombination rate from the PAR test data, two methods, Method-1 and Method-2, introduced by the THAI project, were applied. Since a large gradient of hydrogen concentration developed during hydrogen injection can cause a large error in the hydrogen mass obtained by integrating the measured hydrogen concentrations, a gate was installed at the PAR inlet to homogenize hydrogen in the test vessel before the PAR operation in the tests. A computational fluid dynamics (CFD) code with a PAR model was also applied to evaluate the characteristics of the PAR recombination according to the PAR inlet conditions, and the results were compared with those from Method-1 and Method-2. It was confirmed that the recombination rates from Method-1 require a correction factor to be compatible with results from Method-2 and the CFD simulation in the case of the SPARC-PAR tests.

Safety issues arising from a hydrogen explosion accident in Korea are discussed herein. In order to increase the safety of hydrogen refueling stations (HRSs), the Korea Gas Safety Corporation (KGS) decided to install a damage-mitigation wall, also referred to as a barrier, around the storage tanks at the HRSs after evaluating the consequences of hypothetical hydrogen explosion accidents based on the characteristics of each HRS. To propose a new regulation related to the barrier installation at the HRSs, which can ensure a proper separation distance between the HRS and its surrounding protected facilities in a complex city, KGS planned to test various barrier models under hypothetical hydrogen explosion accidents to develop a standard model of the barrier. A numerical simulation to investigate the effect of the recommended barrier during hypothetical hydrogen explosion accidents in the HRS will be performed before installing the barrier at the HRSs. A computational fluid dynamic (CFD) code based on the open-source software OpenFOAM will be developed for the numerical simulation of various accident scenarios. As the first step in the development of the CFD code, we conducted a hydrogen vapor cloud explosion test with a barrier in an open space, which was conducted by the Stanford Research Institute (SRI), using the modified XiFoam solver in OpenFOAM-v1912. A vapor cloud explosion (VCE) accident may occur due to the leakage of gaseous hydrogen or liquefied hydrogen owing to a failure of piping connected to the storage tank in an HRS. The analysis results using the modified XiFoam predicted the peak overpressure variation from the near field to the far field of the explosion site through the barrier with an error range of approximately ±30% if a proper analysis methodology including the proper mesh distribution in the grid model is chosen. In addition, we applied the proposed analysis methodology using the modified XiFoam to barrier shapes that varied from that used in the test to investigate its applicability to predict peak overpressure variations with various barrier shapes. Through the application analysis, we concluded that the proposed analysis methodology is sufficient for evaluating the safety effect of the barrier, which will be recommended through experimental research, during VCE accidents at the HRSs.

During a severe accident of a light-water reactor, a large amount of water vapor and hydrogen gas are generated, filling up the containment space. The hydrogen concentration in the containment space must be held below the flammable limit, even during a severe accident. The increase and decrease in the water vapor level may result in overpressure and elevation of the hydrogen concentration, respectively. Therefore, the risk of hydrogen in the containment building is closely related to the distribution and behavior of the water vapor. Condensation and evaporation change the concentration of the water vapor. A steam jet is one of the main water vapor condensation mechanisms during the early stages of accident scenarios. We investigated the flow features of the condensation of a steam jet experimentally as well as numerically. For different steam flow rates, flow characteristics induced by water vapor condensation were examined and certain flow features, in this case, the decay and spread of the velocity and temperature were studied. From the numerical study, it was found that a numerical simulation can accurately predict the condensation process from a macroscopic standpoint.

During an accident, hydrogen distribution in a containment building of a nuclear power plant (NPP) and characteristics of hydrogen depletion by passive autocatalytic recombiners (PARs) differ depending on the thermal-hydraulic behaviors occurring in the containment. A spray system installed in the NPP containment to control the pressure in accident conditions may interact with PAR operations. This study intended to experimentally evaluate the hydrogen removal characteristics of a grid-type PAR when a spray was operating. For the experimental simulation of hydrogen recombination characteristics of the PAR affected by a spray operation, we used the SPARC experimental facility, which was equipped with a pressure vessel capable of controlling the wall temperature with a volume of 82 m3. To measure gas species concentrations, 14 probes each for hydrogen, oxygen, and water vapor were installed. Two tests were designed depending on the spray initiation time. The SSP3 test was an experiment to simulate an accident in which the PAR operated as hydrogen was released after the spray is activated, and the SSP4 test was an experiment to simulate an accident in which the spray began after the operation of the PAR was initiated by the hydrogen release. In the experiment, two contradictory results were obtained, which were an increased start-up delay time of the PAR by early initiation of the spray and a negligible impact on the PAR’s performance by the delayed initiation of the spray.

This study was conducted to investigate the effect of absorption coefficient models on the P1 radiation model for a premixed hydrogen flame containing the water vapor. A CFD combustion simulation analysis was performed using XiFoam, one of the open-source CFD solvers in OpenFOAM. The solver using the flamelet combustion model has been modified to implement radiative heat transfer. The absorption coefficient models used in this study the grey-mean model and constant model, and for comparison, case without radiation was added. This CFD simulation study consisted of benchmarking the THAI HD-15 and HD-22 experiments. The difference between the two tests is the inclusion of water vapor in the condition before ignition. In the case of the HD-22 experiment containing water vapor in the initial condition, the simulation results show that the grey-mean absorption coefficient model has a strong influence on the temperature decrease of the flame and on the change in pressure inside the vessel.

We performed a hydrogen combustion analysis in the Advanced Power Reactor 1400 MWe (APR1400) containment during a severe accident initiated by a small break loss of coolant accident (SBLOCA) which occurred at a lower part of the cold leg using a multi-dimensional hydrogen analysis system (MHAS) to confirm the integrity of the APR1400 containment. The MHAS was developed by combining MAAP, GASFLOW, and COM3D to simulate hydrogen release, distribution and combustion in the containment of a nuclear power plant during the severe accidents in the containment of a nuclear power reactor. The calculated peak pressure due to the flame acceleration by the COM3D, using the GASFLOW results as an initial condition of the hydrogen distribution, was approximately 555 kPa, which is lower than the fracture pressure 1223 kPa of the APR1400 containment. To induce a higher peak pressure resulted from a strong flame acceleration in the containment, we intentionally assumed several things in developing an accident scenario of the SBLOCA. Therefore, we may judge that the integrity of the APR1400 containment can be maintained even though the hydrogen combustion occurs during the severe accident initiated by the SBLOCA.

Kallikrein-related peptidase (KLK)6 is associated with inflammatory diseases and neoplastic progression. KLK6 is aberrantly expressed in several solid tumors and regulates cancer development, metastatic progression, and drug resistance. However, the function of KLK6 in the tumor microenvironment remains unclear. This study aimed to determine the role of KLK6 in the tumor microenvironment. Here, we uncovered the mechanism underlying KLK6-mediated cross-talk between cancer cells and macrophages. Compared with wild-type mice, KLK6−/− mice showed less tumor growth and metastasis in the B16F10 melanoma and Lewis lung carcinoma (LLC) xenograft model. Mechanistically, KLK6 promoted the secretion of tumor necrosis factor-alpha (TNF-α) from macrophages via the activation of protease-activated receptor-1 (PAR1) in an autocrine manner. TNF-α secreted from macrophages induced the release of the C-X-C motif chemokine ligand 1 (CXCL1) from melanoma and lung carcinoma cells in a paracrine manner. The introduction of recombinant KLK6 protein in KLK6−/− mice rescued the production of TNF-α and CXCL1, tumor growth, and metastasis. Inhibition of PAR1 activity suppressed these malignant phenotypes rescued by rKLK6 in vitro and in vivo. Our findings suggest that KLK6 functions as an important molecular link between macrophages and cancer cells during malignant progression, thereby providing opportunities for therapeutic intervention.

Hydrogen can be generated by the interactions of the core melt with containment structures and water during severe accident in a nuclear reactor. In case of releasing into the reactor containment, it can induce the hydrogen combustion. It may result in detonation in a nuclear power plant and can threaten the containment integrity. Various mitigation measures such as PAR(passive mitigation system) were prepared to prevent the hydrogen combustion in containment. Although the related safety measures were prepared, Hydrogen combustion is still one of the key issues in nuclear power plant. Many researches on Hydrogen combustion in nuclear power plant have been performed. The large scale experiments on the effect of obstacles and transverse venting on flame acceleration and transition to detonation have been conducted by SNL[1]. Experimental research on hydrogen and fission product behaviour in containments have been done in THAI test facility[2]. Kim et al.[3] have performed numerical analysis of hydrogen flame acceleration in a containment. Combustion is a complex phenomenon accompanying not only heat and mass transfer but also chemical reactions so that the related numerical analysis needs lots of computational resources. Recently various opensource tools such as Cantera[4] and OpenFOAM[5] are available that can handle the problems involving chemical kinetics, thermodynamics and transport process. In this study parametric analysis has been conducted using an open source solver[5] as a preliminary research for the analysis of hydrogen combustion phenomena in a reactor. The numerical model for the analysis was introduced and parameter’s effect was evaluated. The preliminary application on hydrogen flame propagation in a channel has been conducted.

Severe accident mitigation technology was developed and evaluated for a small integral reactor of SMART. The containment pressure and hydrogen behavior were analyzed using MELCOR computer code (Sandia National Laboratory, 2018) in the SBO (Station Black Out) sequence, which was selected from PSA (Probabilistic Safety Assessment) results for the SMART. The severe accident mitigation technology to improve the SMART safety include reactor vessel depressurization using the ADS (Automatic Depressurization System) to prevent DCH (Direct Containment Heating) in case of a reactor vessel failure, a reactor cavity flooding using the CFS (Cavity Flooding System) with the IRWST (In-containment Refueling Water Storage Tank) for the IVR-ERVC (In-Vessel corium Retention through External Reactor Vessel Cooling) to prevent the reactor vessel failure, and a hydrogen control system of PARs (Passive Autocatalytic Recombiners) to remove hazards from hydrogen combustion considering the amount of hydrogen to be generated by 100% fuel cladding oxidation. The MELCOR results showed that the containment pressures during the SBO sequence was below the design pressure, which meant that the containment integrity is maintained during a severe accident in the SMART. The hydrogen mole fraction of the containment was much lower than the hydrogen safety criteria of 10 vol%, which meant that the possi-bility of the hydrogen burn in the containment was negligible. For this reason, it could be concluded that the hydrogen was controlled by the hydrogen moving path and the hydrogen control system of PARs in the SBO sequence of the SMART.

Hydrogen can be generated in the event of a severe accident. By oxidation reactions occurring between fuel cladding materials and high-temperature steam, hydrogen gas is formed. The hydrogen created in the reactor building can be released into the containment building. Investigations have been performed so as to make strategies and means to control hydrogen concentrations inside the containment building during a severe accident. The investigations concerning the hydrogen behavior inside the containment, distribution, combustion, mitigation and interaction with mitigation measures and safety system have been performed. [1] SPARC (Spray-Aerosol-Recombiner-Combustion) test facility constructed in the Korea Atomic Energy Research Institute (KAERI) has been utilized for observation of the hydrogen’s behavior inside the containment building. Experiments about hydrogen behavior interaction with passive auto-catalytic recombiners (PAR) or spray system have been conducted in SPARC test facility. [2] In these experiments, gas analysis system plays an important role in understanding of a hydrogen gas concentration distribution inside the SPARC pressure vessel. This paper described the improvements of gas analysis system and the calibration of gas analyzers.

Background: Radiation therapy, an effective treatment modality against various types of cancer including colorectal cancer, reduces local recurrence rate despite damaging both normal and cancer cells. However, the presence of cancer cells resistant to radiation therapy remains a major therapeutic obstacle; thus, understanding the mechanisms underlying radiation resistance is an important step toward achieving successful outcomes in cancer treatment. Hence, in the present study, radioresistant cell lines were established and the radiation-induced genetic changes associated with radiation resistance were examined.Methods: We generated radioresistant colorectal cancer cell lines and subjected them to RNA sequencing. To know the relationship between CRMP4 downregulation and radiation resistance, western blotting and flow cytometry were used.Results: CRMP4 was identified as the candidate gene associated with radiation sensitivity. The intracellular Ca2+ concentrations increased when cells were exposed to radiation, which in turn, initiated apoptosis. Decreased CRMP4 expression enhanced resistance to radiation and Ca2+ ionophore A23187. Conversely, Ca2+ deficiency by BAPTA-AM caused higher cell death in CRMP4-depleted cells than in CRMP4-expressing cells.Conclusion: Our results indicated that CRMP4 influences Ca2+ signaling pathways involved in apoptosis, and that CRMP4 is critical for radiation sensitivity in colorectal cancer as it can sensitize cancer cells to radiation therapy.

본 연구에서는 SWAT-CUP을 이용하여 밀양댐 상류에 위치한 단장천 유역을 대상으로 목적함수에 따른 매개변수의 보정과 검정을 실시하고 그 적용성을 평가하였다. 단장천 유역은 낙동강 권역 중 하나의 표준유역으로써 유역 면적은 61.9 ㎢이며, 토지 이용은 산림 92.7 %, 농경지가 4.59 %를 차지한다. SWAT 모형의 구동을 위한 수치표고모델, 하천망도, 토지이용도, 토양도는 ArcGIS 10.5를 이용하여 구축하였다. 선정한 23개 매개변수를 SWAT-CUP의 SPE 알고리즘을 이용하여 목적함수를 1개씩 순차적으로 변경하여 1000회 반복 수행하였다. 연구결과, 유출량의 관점에서 보면 목적함수 PBIAS를 적용한 경우 가장 실측유출량과 동일한 결과를 보였으며, P-factor와 R-factor의 결과에서 보면 P-factor 0.88, R-factor 0.56으로 모두 같은 결과값을 보였다. 8개의 목적함수를 적용한 시나리오 중에서 최상의 매개변수 보정결과로써 목적함수 bR²은 P-factor는 0.88, R-factor는 0.56, R²는 0.66, NS는 0.66, PBIAS는 3.0으로 모의 결과가 가장 우수한 수준으로 나타났다. 그러나 같은 조건에서 SWAT-CUP을 이용한 자동보정을 수행하였을 때 8개의 목적함수를 적용하며, 유사한 범위의 매개변수 보정 결과를 나타내기도 했지만 전혀 다른 보정 결과를 나타내기도 하였다. 이러한 결과는 목적함수를 통해 정의되는 SWAT 모형의 불확실성을 나타내며, 향후 이에 대한 연구가 필요할 것으로 판단된다.

For three-dimensional analysis of the thermal hydraulic phenomena associated with hydrogen behavior in a containment building, geometry modelling that reflects the three-dimensional features of the containment building is required. A lot of equipment and concrete structures are installed in the containment building, and gratings are also installed on a large floor area. Gratings in the containment can affect gas flow and heat transfer, so modelling of the grating is required for three-dimensional analysis of hydrogen behavior in the containment. As a method of modelling gratings, many computational mesh nodes are required to directly simulate gratings made of steel plates several millimeters thick, so a large amount of computation is required for accident analysis. Therefore, simple modelling of gratings is required to properly control the size of the three-dimensional mesh. In this study, a method of simulating porous media for gratings was adopted, and the model was extended to allow for consideration of heat transfer of the gratings. To verify the porosity-based grating model, analyses of the H2P1_10_2 experiment recently performed through the international joint project OECD/NEA HYMERES-2 were conducted. Through a comparison with the H2P1_10_2 experimental data, it was confirmed that the porous media-based model showed calculation results very similar to those of the direct simulation of the grating, and that the porous media-based model reduced the mesh size by 1/5 and the calculation time by 1/5 compared to those values in the direct simulation of the grating.

During the severe accident of a nuclear power plant, the hydrogen is generated by the reactor core oxidation which may be stratified or distributed in the containment building. There are risks such as hydrogen explosion at a certain concentration of hydrogen, and therefore a detailed analysis is needed to assess the hydrogen risk. Meanwhile, the spray system operates as part of a severe accident strategy, and the dynamic effects of spray, in particular, are expected to have a significant impact on the gas entrainment and global mixing. Some parameters such as a buoyancy term in a turbulence model and particle diameter affecting the global behavior, have been reported in the previous researches. However, the detailed mechanisms of the dynamic aspect of spray were not described. Thus, the present study aims to perform an in-depth analysis of the effect of the buoyancy term in a turbulence model and the droplet size on the mixing characteristics (mixing tendency and mixing time) in TOSQAN 113 test.