• Journal of the Korean Society for Nondestructive Testing
• /
• v.28 no.4
• /
• pp.364-371
• /
• 2008

Ultrasonic waveguide sensor has been developed for under-sodium viewing of reactor internal structures of a sodium-cooled fast reactor (SFR). The structure design concept of a waveguide sensor assembly was suggested and evaluated for the application in SFR. A 10 m long ultrasonic waveguide sensor assembly has been manufactured and the experimental feasibility tests were carried out. The 10 m long distance propagation performance of zero-order antisymmetric $A_0$ Lamb wave has been verified. The feasibility of ultrasonic waveguide sensor has been demonstrated by the C-scanning resolution performance test.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.25 no.5
• /
• pp.269-278
• /
• 2013

In this study, in order to examine the applicability of computational fluid dynamics with the porous model to the analysis of APR+ (Advanced Power Reactor Plus) internal flow, simulation was conducted with the commercial multi-purpose computational fluid dynamics software, ANSYS CFX V.14. In addition, among the various reactor internals, the effect of flow skirt geometry on reactor internal flow was investigated. It was concluded that the porous model for some reactor internal structures could adequately predict the hydraulic characteristics inside the reactor in a qualitative manner. If sufficient computation resource is available, the predicted core inlet flow distribution is expected to be more accurate, by considering the real geometry of the internal structures, especially located in the upstream of the core inlet. Finally, depending on the shape of the flow skirt, the flow distribution was somewhat different locally. The standard deviation of the mass flow rate (${\sigma}$) for the original shape of flow skirt was smaller, than that for the modified shape of flow skirt. This means that the original shape of the flow skirt may give a more uniform distribution of mass flow rate at the core inlet plane, which may be more desirable for the core cooling.

• Corrosion Science and Technology
• /
• v.20 no.4
• /
• pp.210-229
• /
• 2021

To safely operate domestic nuclear power plants approaching the end of their design life, the material degradation management strategy of the components is important. Among studies conducted to improve the soundness of nuclear reactor components, research methods for understanding the degradation of reactor internals and preparing management strategies were surveyed. Since the IGSCC (Intergranular Stress Corrosion Cracking) initiation and propagation process is associated with metal dissolution at the crack tip, crack initiation sensitivity was decreased in the hydrogenated water with decreased crack sensitivity but occurrence of small surface cracks increased. A stress of 50 to 55% of the yield strength of the irradiated materials was required to cause IASCC (Irradiation Assisted Stress Corrosion Cracking) failure at the end of the reactor operating life. In the threshold-stress analysis, IASCC cracks were not expected to occur until the end of life at a stress of less than 62% of the investigated yield strength, and the IASCC critical dose was determined to be 4 dpa (Displacement Per Atom). The stainless steel surface oxide was composed of an internal Cr-rich spinel oxide and an external Fe and Ni-rich oxide, regardless of the dose and applied strain level.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.20 no.1
• /
• pp.25-31
• /
• 2024

The core shroud of rector vessel internals (RVI) of OPR1000 and ARP1400 is made of Type 304 stainless steel (SS) by bending and welding process that may induce high deformation and residual stress in manufacturing. This work aims to evaluate the susceptibility of stress corrosion crack (SCC) initiation of bent parts of RVI in high temperature primary water environment. For SCC initiation test, tensile specimens were fabricated from the 90 degree bent plate of Type 304 SS (DT specimen), that is an archived part of a Korean APR1400. After the SCC initiation test, the specimen surface was thoroughly examined by optical and scanning electron microscopy, and compared to the specimen fabricated from the as-received plate of Type 304 SS (AR specimen). The surface observation revealed that SCC initiated on the AR specimen surface in typical intergranular (IG) mode, while SCC on the DT specimen occurred in transgrannular mode as well as IG mode. It was also found that the size and number of SCC on the DT specimen were larger than that on the AR specimen. This was attributable to a strain-hardening during the bending process. To compare the susceptibility of SCC initiation, total crack density (TCD) was calculated from the total crack length divided by the measured area of AR and DT specimens. TCD of DT specimen was 4.6 times higher than AR specimen in average, indicating that higher possibility of degradation of bent parts of RVI for a long-term operation.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.44 no.4
• /
• pp.282-293
• /
• 2008

In order to develop the substitutive materials for natural baits of swimming crab pots, the attracting effects of swimming crab such as the preference of baits which were made of the by-products of marine and stock raising through the water tank experiments and fishing experiments. On the investigation of mean entrapped catch number to the pot by the baits after putting the 4 kinds of baits, mackerel(M), mackerel with grinded mackerel s internals($MM_I$), mackerel with tuna s internals$MM_I$) and makerel with grinded krill(MK) each in one pot by turns, $MM_I$ and MK were entrapped mean 3.9(13.0%) and they were a little more comparing to M, and $MT_I$ is least with mean 2.1(7.0%)(F=12.913, P < 0.05). Otherwise, on the preference investigation of swimming crabs by the baits after putting the 4 kinds of baits in the 4 pots each, M was entrapped mean 3.0(10%), but $MM_I$, $MT_I$ and MK were mean 1.2(4.0%), 1.0(3.3%) and 1.5(5.0%) each and they were only 30-50% of M(F=13.398, P < 0.05). On the preference investigation of swimming crabs by the 5 kinds of baits, mackerel(M), and krill(K), manila clam($M_C$), pig s fat($P_F$) and chicken s head($C_H$) which were used in substitutive baits, M was entrapped mean 3.2(10.7%), but K was about 50% of catch of M with mean 1.6(5.3%), and $M_C$, $P_F$ and $C_H$ were very few with mean 0.1-0.2(0.3-0.7%)(F=89.186, P < 0.05). On the preference investigation of swimming crabs by the pots which were put each the 3 kinds of baits, original krill(K), grinded krill with gluten and soybean oil cake($K_GGS$) and grinded krill with gluten, soybean oil cake and glycine($K_GGSG_L$) in the blue fluorescent hexahedral plastic bait cages(BF), and which were put the mackerel(M) in the non-fluorescent hexahedral red plastic bait cage($RF_N$), it was entrapped mean 3.0(10.0%) in the pot which was put the mackerel in the $RF_N$, and the same level in the pots which were put the K and $K_GGSG_L$ in the BF, but it was mean 2.0(6.7%) in the pots which was put the $K_GGS$ in BF and it was decreased by 30% of catch comparing to $RF_N$(F=3.750, P < 0.05). On the preference investigation of swimming crab by the pots which was put grinded tuna with gluten, soybean oil cake and glycine($T_IGSG_L$) in the blue fluorescent hexahedral plastic bait cage(BF), and which was put mackerel(M) in the nonfluorescent hexahedral red plastic bait cage($RF_N$), it was entrapped mean 3.3(11.0%) in the pot which was put mackerel in $RF_N$, and mean 2.7(9.0%) in the pot which was put $T_IGSG_L$ in BF and it was about 15% less comparing to use bait M(t=1.387, P < 0.05). As a results of fishing experiments, a plan for enhancing catching efficiency of $T_IGSG_L$ will be required because catching efficiency of $T_IGSG_L$, alternative bait, was half of fish catching efficiency of natural bait using mackerel. Fishing experiments were conducted 3 times using reinforced substitutive artificial bait that is reinforced attractive effect of $T_IGSG_L$ and composed of tuna intestine, grinded mackerel, gluten, soybean cake, glycine and alanine($T_IM_GGSG_LA$). Catching efficiency of $T_IM_GGSG_LA$ was about 80% of that of natural bait made of mackerel.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.1
• /
• pp.316-322
• /
• 2014

The present study investigated the inflammatory hypersensitivity following activation of the transient receptor potential vanilloid receptor-1(TRPV1) in rats. Experiments were carried out on male Sprague-Dawley rats weighing 220-260g. Following an subcutaneous injection of 5% formalin in the orofacial area, nociceptive scratching behavior was recorded for 9 successive 5-min intervals in rats. The subcutaneous injection of $25{\mu}L$ of 5% formalin produced noxious scratching behavior. Injection of capsaicin, TRPV1 agonist, alone into the vibrissa pad did not produced nociceptive behavior. After subcutaneous injection of capsaicin(0$0.1{\mu}g$, $1{\mu}g/10{\mu}L$) in the formalin-treated rats, nociceptive scratching behavior was recorded for 9 successive 5-min internals. Injection of capsaicin into the vibrissa pad significantly increased the number of scratches at 1 hours after injection. Noxious behavioral responses induced by subcutaneous capsaicin injection were significantly potentiated in formalin-treated rats. Pre or post-treatment with iodo-resinaferatoxin(IRTX), TRPV1 antagonist, significantly attenuated increased nociceptive behavior. These findings suggest that activation of the TRPV1 enhanced formalin-induced inflammatory pain in the orofacial area of rats.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.44 no.3
• /
• pp.174-183
• /
• 2008

In order to develop the substitutive materials for natural baits of swimming crab pots, the fluorescent characteristics of the baits were analyzed, and the preference of fluorescent dyes were investigated by the mean entrapped catch number to the pots through the water tank experiments and fishing experiments. On the investigation of fluorescent characteristics by the 5 kinds of baits, mackerel, krill, manila clam, pig's fat and chicken's head which were used in substitutive baits for test in the UV long wave(365nm) area, it showed clear blue fluorescence in the skin of mackerel, shell of krill, manila clam and bill of chicken's head, and green fluorescence in the mackerel s muscle and internals, and yellow fluorescence in the pig's fat and chicken's head. On the investigation of fluorescent characteristics by the bait cages in the UV short wave(254nm) and long wave(365nm) area, it showed each green, red and blue fluorescence in the cylinderical or hexahedral red plastic bait cages which were painted each green, red and blue fluorescence dyes, but it showed yellowish green flourescence in the cylinderical or hexahedral red plastic bait cage which was painted yellow fluorescent dye. On the preference investigation of the fluorescent dyes of swimming crabs by the 5 kinds of the bait cages which were put the mackerel in the non-fluorescent red plastic cage($RF_N$), red, yellow, green and blue fluorescent plastic cages(RF, YF, GF, BF) each, nonfluorescent red plastic cage($RF_N$) was entrapped mean 2.0(6.7%), but blue fluorescent plastic cage(BF) was mean 5.0(16.7%) and it was more 2.5 times comparing to $RF_N$, and red fluorescent cage(RF) was same level and green fluorescent cage(GF) was 50% of catch number comparing to $RF_N$, and yellow fluorescent cage(YF) was entrapped nothing(F 46.324, P < 0.05). On the investigation of the entrapped catch number to the pots which were put the mackerel in the blue fluorescent hexahedral plastic cage(HP) and blue fluorescent silicon mackerel model cage(SM), HP was mean 3.4(11.3%) and it was a little more comparing to SM which was entrapped mean 3.2(10.7%)(t 0.775, P > 0.05). Fishing experiments on the preference investigation of swimming crabs by the pots which were put in the non-fluorescent red plastic cage($RF_N$) and blue fluorescent plastic cage(BF) were conducted 3 times. Mean catching number and weight of $RF_N$ were 71.7 ind.(18.3%) and 16.9kg(64.3%), and those of BF were 93.0 ind.(23.1%) and 19.8kg(64.5%), respectively.

• Fire Science and Engineering
• /
• v.28 no.4
• /
• pp.21-28
• /
• 2014

This study obtained the following results by analyzing the standards related to a $1{\phi}$ 2W MCCB and evaluating its heat resistance characteristics. Since KS C 8321 corresponds to IEC 60947-2 standards, most of the related regulations are similar. The NFPA, which presents the user oriented safety regulations, contains no details about tests or inspections, etc., but it does specify in detail the regulations directly related to safety. It can be seen that KS C 8321 classifies in detail the items about tests and inspections. However, IEC 60947-2 and IEEE C37.51 simplified the test and inspection items or omitted some of them. When applying thermal stress to an MCCB for 6 hours at $180^{\circ}C$ using a heat resistant experimental device, it was found that the actuator lever was transformed and moved in the tripped state. In addition, most of the fixing hanger was melted down, losing their function. When applying thermal stress to the MCCB at $90^{\circ}C$, it showed nothing peculiar, but the fixing hanger was partly deformed at $105^{\circ}C$ and $120^{\circ}C$. It was found that the fixing hanger was deformed and the name plate was discolored at $150^{\circ}C$. It can be seen from the analysis of the internals of the MCCB that the trip bar has been melted away and that the up and down operator has moved up. The experiment performed by applying a withstanding voltage of 6 kV for 60 s showed that all items remained intact. In addition, the evaluation of the insulation performance performed by applying DC 500 V using an insulation-resistance tester showed good insulation performance.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.17 no.4
• /
• pp.437-445
• /
• 2019

After the permanent shutdown of K1 in 2017, decommissioning processes have attracted great attention. According to the current decommissioning roadmap, the dismantling of the activated components of K1 may start in 2026, following the removal of its spent fuel. Since the reactor vessel (RV) and reactor vessel internal (RVI) of K1 contain massive components and are relatively highly activated, their decommissioning process should be conducted carefully in terms of radiological and industrial safety. For achieving maximum efficiency of nuclear waste management processes for K1, we present activation analysis of the segmentation process and waste classification of the RV and RVI components of K1. For RVI, the active fuel regions and some parts of the upper and lower active regions are classified as intermediate-level waste (ILW), while other components are classified as low-level waste (LLW). Due to the RVI's complex structure and high activation, we suggest various underwater segmentation techniques which are expected to reduce radiation exposure and generate approximately nine ILW and nineteen very low level waste (VLLW)/LLW packages. For RV, the active fuel region and other components are classified as LLW, VLLW, and clearance waste (CW). In this case, we suggest in-situ remote segmentation in air, which is expected to generate approximately forty-two VLLW/LLW packages.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.15 no.4
• /
• pp.403-409
• /
• 2017

For dry storage of the spent nuclear fuel (SNF) stored in the storage pool of a nuclear power plant, essentially all moisture must be removed to prevent corrosion of the assembly and canister internals and/or degradation of fuel cladding integrity after SNF canister loading operation. R&D work is now in progress on a forced gas drying system that can be used to remove residual water in canisters. In this work, preliminary design is performed to manufacture the forced gas drying system. This process includes a case study of dry methods for canister moisture removal, relative codes and standards, confirmation of adequate dryness, needs analysis at plant sites, and characteristics of SNF stored in pools. Through this preliminary design work, we obtained a conceptual flow diagram and preliminary P&ID of the forced gas drying system. The results of this study can be used to determine details of the design to manufacture the forced gas drying system.