Uncertainty analysis of ROSA/LSTF test by RELAP5 code and PKL counterpart test concerning PWR hot leg break LOCAs

Takeshi Takeda,Iwao Ohtsu 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.6

An experiment was conducted for the OECD/NEA ROSA-2 Project using the large-scale test facility (LSTF),which simulated a 17% hot leg intermediate-break loss-of-coolant accident in a pressurized water reactor(PWR). In the LSTF test, core uncovery started simultaneously with liquid level drop in crossover legdownflow-side before loop seal clearing, and water remaining occurred on the upper core plate in theupper plenum. Results of the uncertainty analysis with RELAP5/MOD3.3 code clarified the influences ofthe combination of multiple uncertain parameters on peak cladding temperature within the defineduncertain ranges. For studying the scaling problems to extrapolate thermal-hydraulic phenomenaobserved in scaled-down facilities, an experiment was performed for the OECD/NEA PKL-3 Project withthe Primarkreislaufe Versuchsanlage (PKL), as a counterpart to a previous LSTF test. The LSTF testsimulated a PWR 1% hot leg small-break loss-of-coolant accident with steam generator secondary-sidedepressurization as an accident management measure and nitrogen gas inflow. Some discrepanciesappeared between the LSTF and PKL test results for the primary pressure, the core collapsed liquid level,and the cladding surface temperature probably due to effects of differences between the LSTF and thePKL in configuration, geometry, and volumetric size.

ROSA/LSTF test and RELAP5 code analyses on PWR 1% vessel upper head small-break LOCA with accident management measure based on core exit temperature

Takeshi Takeda 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.8

An experiment was performed using the large-scale test facility (LSTF), which simulated a 1% vesselupper head small-break loss-of-coolant accident with an accident management (AM) measure under anassumption of total-failure of high-pressure injection (HPI) system in a pressurized water reactor (PWR). In the LSTF test, liquid level in the upper head affected break flow rate. Coolant was manually injectedfrom the HPI system into cold legs as the AM measure when the maximum core exit temperaturereached 623 K. The cladding surface temperature largely increased due to late and slow response of thecore exit thermocouples. The AM measure was confirmed to be effective for the core cooling. TheRELAP5/MOD3.3 code indicated insufficient prediction of primary coolant distribution. The authorconducted uncertainty analysis for the LSTF test employing created phenomena identification andranking table for each component. The author clarified that peak cladding temperature was largelydependent on the combination of multiple uncertain parameters within the defined uncertain ranges.

ROSA/LSTF Test and RELAP5 Analyses on PWR Cold Leg Small-Break LOCA with Accident Management Measure and PKL Counterpart Test

Takeshi Takeda,Iwao Ohtsu 한국원자력학회 2017 Nuclear Engineering and Technology Vol.49 No.5

An experiment using the Primӓrkreislӓufe Versuchsanlage (PKL) was performed for the OECD/NEA PKL-3Project as a counterpart to a previous test with the large-scale test facility (LSTF) on a cold leg smallbreakloss-of-coolant accident with an accident management (AM) measure in a pressurized waterreactor. Concerning the AM measure, the rate of steam generator (SG) secondary-side depressurizationwas controlled to achieve a primary depressurization rate of 200 K/h as a common test condition;however, the onset timings of the SG depressurization were different from each other. In both tests, rapidrecovery started in the core collapsed liquid level after loop seal clearing, which caused whole corequench. Some discrepancies appeared between the LSTF and PKL test results for the core collapsed liquidlevel, the cladding surface temperature, and the primary pressure. The RELAP5/MOD3.3 code predictedthe overall trends of the major thermal-hydraulic responses observed in the LSTF test well, and indicateda remaining problem in the prediction of primary coolant distribution. Results of uncertainty analysis forthe LSTF test clarified the influences of the combination of multiple uncertain parameters on peakcladding temperature within the defined uncertain ranges.

Resistance to UV radiation in the two-spotted spider mite, Tetranychus urticae

Takeshi Suzuki,Makio Takeda 한국응용곤충학회 2008 한국응용곤충학회 학술대회논문집 Vol.2008 No.10

Why do two-spotted spider mites (Tetranychus urticae) inhabit on the underside of leaves? Why are diapause females orange? A possible key to answering these questions is ultraviolet (UV) radiation. UV radiation directly damages DNA and produces reactive oxygen species (ROS). ROS also damages DNA, dissociates proteins, and oxidizes lipids. Because mites are small, the UV/ROS-induced damage would be lethal to mites. In non-diapause females, mortalities under UV-C (250 nm) at 0.6 W m–2 and UV-B (300 nm) at 2.4 W m–2 were significantly higher than those under continuous darkness (DD; control). Oviposition rates in such treatments were significantly lower than those under DD. No significant effects for mortality and oviposition rate were observed under UV-A (350 nm) even when the intensity was as high as 2.4 W m–2. In diapause females, the differences in mortalities between all types of UV radiation and DD were not significant. Interestingly, more than half of diapause females escaped from leaf disks under all types of UV radiation, and the escape rates were significantly higher than those under DD and those for non-diapause females. This suggests that diapause females exhibit negative phototaxis. Mites inhabit the underside of leaves in summer with dense vegetation. Most of UV radiation is absorbed and reflected by leaves. Therefore, the underside of leaves is considered a suitable environment for mites to avoid UV radiation, particularly UV-B (UV-C is completely absorbed by the ozone layer). In autumn, leaves start turning yellow and red as winter approaches and finally, fall. During this phenological event, the UV-B level in the plant canopy would increases dramatically while female mites enter diapause with a change in their body color from yellow-green to orange. It is known that the orange color is mainly due to the accumulation of β-carotene, which plays a role as a scavenger of ROS. Therefore, low mortalities observed in diapause females under UV-C and UV-B may be a result of β-carotene accumulation or merely due to the increase in the escape rate. Therefore, whether the escaped diapause females are resistant to UV-C and UV-B damage needs to be confirmed. Our findings suggest that UV radiation is utilized as an effective non-chemical measure to reduce the mite population and that the selection of habitat and change in body color is the mite’s strategy to reduce the deleterious effects of UV-B.

ROSA/LSTF test and RELAP5 code analyses on PWR steam generator tube rupture accident with recovery actions

Takeshi Takeda 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.6

An experiment was performed for the OECD/NEA ROSA-2 Project with the large-scale test facility (LSTF),which simulated a steam generator tube rupture (SGTR) accident due to a double-ended guillotine breakof one of steam generator (SG) U-tubes with operator recovery actions in a pressurized water reactor. Therelief valve of broken SG opened three times after the start of intact SG secondary-side depressurizationas the recovery action. Multi-dimensional phenomena specific to the SGTR accident appeared such assignificant thermal stratification in a cold leg in broken loop especially during the operation of highpressureinjection (HPI) system. The RELAP5/MOD3.3 code overpredicted the broken SG secondarysidepressure after the start of the intact SG secondary-side depressurization, and failed to calculatethe cold leg fluid temperature in broken loop. The combination of the number of the ruptured SG tubesand the HPI system operation difference was found to significantly affect the primary and SG secondarysidepressures through sensitivity analyses with the RELAP5 code.

Outcomes of partially covered self-expandable metal stents with different uncovered lengths in endoscopic ultrasound-guided hepaticogastrostomy: a Japanese retrospective study

Takeshi Okamoto,Takashi Sasaki,Tsuyoshi Takeda,Tatsuki Hirai,Takahiro Ishitsuka,Manabu Yamada,Hiroki Nakagawa,Takafumi Mie,Takaaki Furukawa,Akiyoshi Kasuga,Masato Ozaka,Naoki Sasahira 대한소화기내시경학회 2024 Clinical Endoscopy Vol.57 No.4

Background/Aims: The optimal length of the uncovered portion of partially covered self-expandable metal stents (PCSEMSs) used in endoscopic ultrasound-guided hepaticogastrostomy (EUS-HGS) remains unclear. This study investigated the safety and efficacy of PCSEMSs with different uncovered lengths, with a focus on stent migration and time to recurrent biliary obstruction (RBO). Methods: Outcomes of patients undergoing EUS-HGS using PCSEMSs with 5-mm and 20-mm uncovered portions at our institution from January 2016 to December 2021 were compared. Results: Sixty-two patients underwent EUS-HGS using PCSEMS (5/20-mm uncovered portions: 32/30). Stent migration occurred only in the 5-mm group. There were no differences in RBO rates (28.1% vs. 40.0%) or median time to RBO (6.8 vs. 7.1 months) between the two groups. Median overall survival (OS) was longer in the 20-mm group (3.1 vs. 4.9 months, p=0.037) due to the higher number of patients that resumed chemotherapy after EUS-HGS (56.7% vs. 28.1%, p=0.029). Good performance status, absence of hepatic metastases, and chemotherapy after EUS-HGS were independent predictors of longer OS. Conclusions: No migration was observed in patients treated with PCSEMS with 20-mm uncovered portions. Patients treated with PCSEMS with 20-mm uncovered portions performed at least as well as those treated with 5-mm uncovered portions in all material respects.

Rotatable sphincterotome as a rescue device for endoscopic retrograde cholangiopancreatography cannulation: a single-center experience

Takeshi Okamoto,Takashi Sasaki,Tsuyoshi Takeda,Takafumi Mie,Chinatsu Mori,Takaaki Furukawa,Yuto Yamada,Akiyoshi Kasuga,Masato Matsuyama,Masato Ozaka,Naoki Sasahira 대한소화기내시경학회 2024 Clinical Endoscopy Vol.57 No.1

Background/Aims: Selective bile duct or pancreatic duct cannulation remains a significant initial hurdle in endoscopic retrograde cholangiopancreatography (ERCP) despite advances in endoscopy and accessories. This study evaluated our experience with a rotatable sphincterotome in cases of difficult cannulation. Methods: We retrospectively reviewed ERCP cases using TRUEtome, a rotatable sphincterotome, as a rescue device for cannulation at a cancer institute in Japan from October 2014 to December 2021. Results: TRUEtome was used in 88 patients. Duodenoscopes were used for 51 patients, while single-balloon enteroscopes (SBE) were used for 37 patients. TRUEtome was used for biliary and pancreatic duct cannulation (84.1%), intrahepatic bile duct selection (12.5%), and strictures of the afferent limb (3.4%). Cannulation success rates were similar in the duodenoscope and SBE groups (86.3% vs. 75.7%, p=0.213). TRUEtome was more commonly used in cases with steep cannulation angles in the duodenoscope group and in cases requiring cannulation in different directions in the SBE group. There were no significant differences in adverse events between the two groups. Conclusions: The cannulation sphincterotome was useful for difficult cannulations in both unaltered and surgically altered anatomies. It may be an option to consider before high-risk procedures such as precut and endoscopic ultrasound-guided rendezvous techniques.

Comparison of tube-assisted mapping biopsy with digital single-operator peroral cholangioscopy for preoperative evaluation of biliary tract cancer

Tsuyoshi Takeda,Takashi Sasaki,Takafumi Mie,Takeshi Okamoto,Chinatsu Mori,Takaaki Furukawa,Yuto Yamada,Akiyoshi Kasuga,Masato Matsuyama,Masato Ozaka,Naoki Sasahira 대한소화기내시경학회 2022 Clinical Endoscopy Vol.55 No.4

Background/Aims: Digital single-operator cholangioscopy (DSOC)-guided mapping biopsy (DMB) and tube-assisted mapping biopsy(TMB) are two techniques used for preoperative evaluation of biliary tract cancer (BTC). However, data regarding the diagnostic performanceof these techniques are limited. Methods: We retrospectively examined consecutive patients with BTC who underwent either technique at our institution between2018 and 2020. We evaluated the technical success rate, adequate tissue acquisition rate, and diagnostic performance of these techniquesfor the evaluation of lateral spread of BTC. Results: A total of 54 patients were included in the study. The technical success rate of reaching the target sites was 95% for DMB and100% for TMB. The adequate tissue acquisition rate was 61% for DMB and 69% for TMB. The adequate tissue acquisition rate was low,especially for target sites beyond the secondary biliary radicles. The sensitivity of DMB alone was 39%, which improved to 65% whencombined with visual impression. Experts demonstrated a higher negative predictive value and diagnostic accuracy with respect toboth DSOC visual impression and DMB for the evaluation of lateral spread of BTC compared to trainees. Conclusions: Adequate tissue acquisition rates were similar between the two techniques. Since DMB requires expertise, TMB may bean acceptable option when DSOC is unavailable or when DSOC expertise is limited.

Prediction of random-regression coefficient for daily milk yield after 305 days in milk by using the regression-coefficient estimates from the first 305 days

Yamazaki, Takeshi,Takeda, Hisato,Hagiya, Koichi,Yamaguchi, Satoshi,Sasaki, Osamu Asian Australasian Association of Animal Productio 2018 Animal Bioscience Vol.31 No.10

Objective: Because lactation periods in dairy cows lengthen with increasing total milk production, it is important to predict individual productivities after 305 days in milk (DIM) to determine the optimal lactation period. We therefore examined whether the random regression (RR) coefficient from 306 to 450 DIM (M2) can be predicted from those during the first 305 DIM (M1) by using a RR model. Methods: We analyzed test-day milk records from 85,690 Holstein cows in their first lactations and 131,727 cows in their later (second to fifth) lactations. Data in M1 and M2 were analyzed separately by using different single-trait RR animal models. We then performed a multiple regression analysis of the RR coefficients of M2 on those of M1 during the first and later lactations. Results: The first-order Legendre polynomials were practical covariates of RR for the milk yields of M2. All RR coefficients for the additive genetic (AG) effect and the intercept for the permanent environmental (PE) effect of M2 had moderate to strong correlations with the intercept for the AG effect of M1. The coefficients of determination for multiple regression of the combined intercepts for the AG and PE effects of M2 on the coefficients for the AG effect of M1 were moderate to high. The daily milk yields of M2 predicted by using the RR coefficients for the AG effect of M1 were highly correlated with those obtained by using the coefficients of M2. Conclusion: Milk production after 305 DIM can be predicted by using the RR coefficient estimates of the AG effect during the first 305 DIM.

Phenotypic Relationship between Lactation Persistency and Change in Body Condition Score in First-lactation Holstein Cows

Yamazaki, Takeshi,Takeda, Hisato,Nishiura, Akiko,Sasai, Youji,Sugawara, Naoko,Togashi, Kenji Asian Australasian Association of Animal Productio 2011 Animal Bioscience Vol.24 No.5

We examined the correlations between lactation curve shape, including persistency and changes in body condition score (BCS) during early-stage (0 to 30 days in milk (DIM)), nadir-stage (31 to 90 DIM), and late-stage (91 to 240 DIM) lactation in 191 first-lactation cows. Data used were first-parity BCS records, scored twice every month after calving, and daily milk yields. Individual lactation curves were depicted by the Wilmink function. Lactation persistency was defined as the difference in estimated milk yields between 240 DIM and 60 DIM. Changes in BCSs in the early and late stages were defined as linear regression coefficients. There were no significant correlations between traits for lactation curve shape and change in BCS in early-stage lactation. Peak yield and total milk yield were negatively correlated with BCSs in nadir- and late-stage lactation and with BCS change in late-stage lactation, suggesting that cows with high lactation yields had low body reserves and health status in mid- to late lactation and had delayed recovery of body reserves. Lactation persistency was positively correlated with change in BCS in late-stage lactation, suggesting that cows with high lactation persistency tended to be healthy and to recover their body reserves well in late lactation.