• Nuclear Engineering and Technology
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• v.53 no.11
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• pp.3517-3527
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• 2021

New 80-MW (electric) ultra-long-life sodium cooled fast reactor core having inherent safety characteristics is designed with heterogeneous fuel assemblies comprised of driver and blanket fuel rods. Several options using upper sodium plenum and SSFZ (Special Sodium Flowing Zone) for reducing sodium void reactivity are neutronically analyzed in this core concept in order to improve the inherent safety of the core. The SSFZ allowing the coolant flow from the peripheral fuel assemblies increases the neutron leakage under coolant expansion or voiding. The Monte Carlo calculations were used to design the cores and analyze their physics characteristics with heterogeneous models. The results of the design and analyses show that the final core design option has a small burnup reactivity swing of 618 pcm over ~54 EFPYs cycle length and a very small sodium void worth of ~35pcm at EOC (End of Cycle), which leads to the satisfaction of all the conditions for inherent safety with large margin based on the quasi-static reactivity balance analysis under ATWS (Anticipated Transient Without Scram).

• Nuclear Engineering and Technology
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• v.53 no.6
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• pp.1747-1755
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• 2021

This paper presents floating absorber for safety at transient (FAST) which is a passive safety device for sodium-cooled fast reactors with a positive coolant temperature coefficient. Working principle of the FAST makes it possible to insert negative reactivity passively in case of temperature rise or voiding of coolant. Behaviors of the FAST in conventional oxide fuel-loaded and metallic fuel-loaded SFRs are investigated assuming anticipated transients without scram (ATWS) scenarios. Unprotected loss of flow (ULOF), unprotected loss of heat sink (ULOHS), unprotected transient overpower (UTOP) and unprotected chilled inlet temperature (UCIT) scenarios are simulated at end of life (EOL) conditions of the oxide and the metallic SFR cores, and performance of the FAST to improve the reactor safety is analyzed in terms of reactivity feedback components, reactor power and maximum temperatures of fuel and coolant. It is shown that FAST is able to improve the safety margin of conventional burner-type SFRs during ULOF, ULOHS, UTOP and UCIT.

• Clinical and Experimental Pediatrics
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• v.49 no.6
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• pp.653-658
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• 2006

Purpose : Because voiding cystourethrography(VCUG) is an invasive method, we studied whether VCUG could be postponed through evaluation of alternative non-invasive tests including renal ultrasonography and $^{99m}Tc$-DMSA renal scan. Methods : We reviewed the medical records of 175 patients initially diagnosed with febrile urinary tract infection during the one year period of 1999, and compared 3-tests : renal ultrasongraphy, $^{99m}Tc$-DMSA renal scan, and VCUG. Results : Renal ultrasonography didn't contribute to the prognostication of pyelonephritis(photopenic areas) or vesicoureteral reflux(VUR). Presentation of photopenic areas in $^{99m}Tc$-DMSA renal scan was related to VUR. If both findings of renal ultrasonography and $^{99m}Tc$-DMSA renal scans were normal, this condition was closely related to normal results in VCUG. And if both examinations were abnormal, the condition was closely related to VUR. But this state could not always guarantee the normal result from VCUG because of low sensitivity in finding VUR. Conclusion : In cases in which acute phyelonephritis is demonstrated by $^{99m}Tc$-DMSA renal scan, VCUG is required. In addition to this, if the conditions of hydronephrosis, vesicoureteral dilatation, increases of renal volume, and changes of echogenesity are shown by renal ultrasonography, VCUG should be performed. If a patient has difficulty undergoing VCUG, temporary postponement of VCUG can be taken into consideration, but only in cases where both examinations of renal ultrasonography and $^{99m}Tc$-DMSA renal scan are normal. Nevertheless, close observation is be advised even in this case.

• Childhood Kidney Diseases
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• v.9 no.2
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• pp.201-212
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• 2005

Purpose : Acute pyelonephritis is one of the most common causes of unexplained fever in children. It may lead to the development of progressive renal damage. However, the deteclion of acute pyelonephritis can be difficult, especially in infants. The objective of this study was to evaluate the diagnostic value of various lab tests and imaging studies for acute renal parenchymal changes in children with APN. We correlated the clinical and laboratory manifestations of acute pyelonephritis with the Imaging studies. Methods : We reviewed the records of 115 children (85 males and 30 females) who were hospitalized Outing the period of January 1998 to December 2002 with initial clinical symptoms suggestive of pyelonephritis. The patients' age, sex, duration of fever, laboratory findings, and causative organisms were compared with the findings of imaging studies (Technetium-99m dimercaptosuccinic acid renal scan, renal ultrasonography, intravenous pyelography, voiding cystourethrography). Results : No significant relation between the number of febrile days, leukocyte count, causative organism, and the renal abnormalities in the imaging studies were observed. On the other hand, both C-reactive protein and erythrocyte sedimentation rate levels were significantly elevated in children with positive dimercaptosuccinic acid renal scan. Furthermore, females and children older than 1 year presented with significantly higher rate of abnormal dimercaptosuccinic acid renal scan findings and vesicoureteral reflux presented by voiding cystourethrography. Conclusion : We recommend females and children older than 1 year who are suspected of acute pyelonephritis be evaluated carefully for renal involvement by performing imaging studies including dimercaptosuccinic acid renal scan and voiding cystourethrography. (J Koroan Soc Pediatr Nephrol 2005;9:201-212)

• Childhood Kidney Diseases
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• v.15 no.2
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• pp.163-171
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• 2011

Purpose : To evaluate the prevalence of vesicoureteral reflux (VUR) according to the timing of voiding cystourethrography (VCUG) in infantile urinary tract infection (UTI). Methods : The data of 134 infants (1-12 months) with renal cortical defect in $^{99m}Tc$-2, 3-dimercaptosuccinic acid ($^{99m}Tc$-DMSA) scan with a diagnosis of UTI in two hospitals from 2000 to 2010 were retrospectively analyzed. The VCUG was performed after 2 weeks from the diagnosis of UTI in Group I (n=68), and the VCUG was performed within 2 weeks from the diagnosis of UTI in Group II (n=66). Results : There were no significant differences between the two groups in the duration of fever, white blood cell count, C-reactive protein levels, and abnormalities in ultrasonography (P>0.05). There was no significant difference between the two groups in the prevelence of VUR, bilateral VUR, and severe VUR. VCUG-induced UTI was detected 16 (23.5%) of patients in whom the procedure was performed 2 weeks after the diagnosis, and none of VCUG-induced UTI occurred in those in whom the procedure was performed 2 weeks within the diagnosis. Conclusion : We conclude that the prevalence of VUR according to the timing of VCUG did not differ between the two groups in infantile UTI with renal cortical defect in DMSA scan. We also found that performing VCUG with antibiotics can decrease risk of VCUG-induced UTI.

• Childhood Kidney Diseases
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• v.1 no.1
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• pp.53-59
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• 1997

There have been many recent reports that unilateral renal agenesis and multicystic dysplastic kidneys are accompanied by contralateral vesicoureteral reflux leading to its injury. We grouped the children with unilateral renal agenesis, renal hypoplasia, multicystic dysplastic kidney into abnormal unilateral renal development and investigated whether it was accompanied with contralateral vesicoureteral reflux. We retrospectively reviewed 96 pediatric cases of unilateral renal agenesis, hypoplasia, multicystic dysplastic kidney diagnosed at Shinchon Severance Hospital, Yongdong Severance Hospital from 1987 to 1996 and Ajou University Hospital from 1994 to 1996. Diagnosis was based on radiological findings, renal hypoplasia being defined as small renal size with no apparent renal scarring and no irregularity of the calyceopelvic system on abdominal sonography or intravenous pyelography. Among the 96 cases,48 cases carried out voiding cystourethrography. 58 cases were male(60%) and 38 cases were female(40%). The cases of abnormal unilateral development on the left side were 45(47%) and that on the right side were 51(53%). Although there were diverse reasons leading to diagnosis, the major ones included were prenatal sonography, urinary tract infection, and other congenital anomalies. In cases of unilateral renal agenesis & hypoplasia the leading factors were urinary tract infection & other congenital anomalies and in cases of multicystic dysplastic kidney that was prenatal sonography. There was a chronological gap between the mean age of diagnosis(1.8 year) and voiding cystouerthrography(2.5 year, P < 0.01). 9 of the 18 unilateral renal agenesis cases, 5 of the 11 unilateral renal hypoplasia cases, and 3 of the 19 unilateral multicystic dysplastic kidney cases showed contralateral vesicoureteral reflux. Average reflux grade was above G III.Among the 17 children who had contralateral vesicoureteral reflux, 3 children had chronic renal failure and ureteroneocystostomy was carried out in 6 children. From the above results we conclude that screening voiding cystourethrography should be performed in children with abnormal unilateral renal development for early detection of vesicoureteral reflux in the contralateral kidney.

• Childhood Kidney Diseases
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• v.11 no.1
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• pp.65-73
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• 2007

Purpose : Voiding cystourethrography(VCUG) is a commonly performed diagnostic procedure in children with urinary tract infections. Recently, with the widespread use of prenatal ultrasonography, VCUG is performed as part of the postnatal radiological evaluation of asymptomatic infants with prenatally detected hydronephrosis. The procedure is relatively simple but it involves discomfort and some complications. We studied post procedural symptoms and complications in children who underwent VCUG. Methods : This study reviewed 259 patients who underwent VCUG in our hospital between October 2005 and September 2006. We did a chart review and a telephone interview with the patients' parents about symptoms and complications associated with VCUG. Results : Among 269 children, 217 patients(80.7%) were under 2 years of age and 5 patients (1.9%) were over 8 years of age. Their mean age was $13.1{\pm}22.9$ months. After VCUG, dysuria was found in 49 patients presented with dysuria, and irritability in 36 patients with irritability. Other complications were hematuria, fever, frequency, bladder rupture and urinary tract infection. Mean symptoms duration was $1.4{\pm}0.7$ days. There was no significant relationship between prophylactic antibiotics use and complication rate associated with VCUG. Conclusion : Our study demonstrated that 32.7% of patients showed complications including bladder rupture and urinary tract infection after VCUG. We also found that prophylactic antibiotics use did not prevent urinary tract infection nor decrease the rate of complications associated with VCUG. Therefore, we suggest that the procedure must be done carefully and aseptically, and we should closely observe the children who undergo VCUG for development of possible complications.

• Journal of the Korean Society of Radiology
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• v.9 no.7
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• pp.529-533
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• 2015

VCUG(Voiding Cystourethrography) study is being performed to check urinary reflex symptom from bladder to ureter or kidney in the method of filling the bladder with radiation opaque contrast agent. However, VCUG study have been performed impersonally, patients have to be naked and open their legs and then void. This method is so impersonal that it is immediately needed to improve the way of testing and crete new aid. Therefore, this study through producing underwear for VCUG, analysis and compares the test time of VCUG, patient radiation dose and patient satisfaction. The target of this study was 79 Male and Female patients who visited genitourinary clinic of PNUYH for their VCUG tests AXIUM Iconos R200(Siemens Medical System : Germany) and self-produced plastic underwears made by vinyl and plasic molding machine were used. The 79 patient were divided into two groups : experiment of patient and comparison group of we patient (using aid) in order to compare, testing time, DAP (dose area product) and patient satisfaction. There was time reduction, from 35.3min of comparison group to 27.8min experimentation group by 7.5min decrease. And comparison group of $4566.6{\mu}Gym^2$(DAP) decreased experimental group (using aid) of $3411.9{\mu}Gym^2$ by $1154.7{\mu}Gym^2$. In the case of patients satisfaction study, anxiety had a drop by 3.45 of comparison group to 2.51 experimentation group by 0.94 decrease. in experimental group. And shame had a drop by 4.02 of comparison group to 3.08 experimentation group by 0.94 increase. in experimental group. Difference of the smooth voiding had a drop by 1.90 of comparison group to 2.84 experimentation group by 0.94 increase. in experimental group. In addition satisfaction had a rise by 1.19 in experimental group. There were also other opinions of uncomfortableness on it and troublesome to wear. VCUG is one of the sensitive care required test. Therefore staff and the aid can give patients such comfortable and the aid can consentive on voiding. As a result test time and DAP can be reduced. It is needed to make testing at more comfortable for patients.

• Childhood Kidney Diseases
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• v.12 no.1
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• pp.54-61
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• 2008

Purpose: This study was performed to assess necessity of voiding cystourethrography (VCUG) for infants with urinary tract infection (UTI) who had both normal renal sonography and normal DMSA renal scans. Methods: We reviewed 117 infants hospitalized for UTI between February 2002 and July 2007 at Sanggye Paik Hospital. The diagnosis of UTI was made by culture from a urine specimen obtained by suprapubic puncture(n=57), catheterization(n=58), or collection bag method (n=2, twice positive culture of the same organism). All patients had undergone renal sonography, DMSA renal scan and VCUG. Children with both normal renal sonography and normal DMSA renal scans were evaluated for the presence or severity of vesicoureteral reflux (VUR). Results: Of the 117 patients, 96 were boys and 21 were girls. 28 patients(23.9%) had VUR. 59(50.4%) showed both normal renal sonography and normal DMSA renal scans. Among these 59 patients, 7(11.9%) showed VUR. Three of them had grade I-II reflux, two grade III reflux, and the other two grade IV reflux. One of them showed bilateral VUR, grade IV reflux on the right and grade III on the left. Conclusion: Although the negative predictive value of both normal renal sonography and normal DMSA renal scan for VUR was 88.1%, 7 patients had VUR and two of them had high grade reflux(grade IV). So, we suggest that VCUG should be performed in infants with UTI despite both normal renal sonography and normal DMSA renal scans.

• Childhood Kidney Diseases
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• v.12 no.2
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• pp.194-201
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• 2008

Purpose : Voiding cystourethrography(VCUG) is required to detect vesicoureteral reflux(VUR), which may manifest as urinary tract infection(UTI) in children. It is well known that VCUG can cause UTI(post-VCUG UTI). In this study, risk factors for post-VCUG UTI and the preventive effect of antibiotics against this complication of VCUG were explored. Methods : Medical records of 284 patients who underwent VCUG at our hospital in 2007 were reviewed retrospectively. The incidence of post-VCUG UTI and risk factors for post-VCUG UTI, and the impact of antibiotic use on prevention of post-VCUG UTI were evaluated. According to antibiotics usage, we divided the enrolled patients into 4 groups of noantibiotics group, prophylactic antibiotics group(prophylactic antibiotics having been used before), antibiotics-for-VCUG group(antibiotics added for VCUG) and antibiotics-for-treatment group(treatment dose of antibiotics). Results : Seven of 284 children(2.5%) developed UTI after they underwent VCUG. Highgrade(grade$\geq$III) VUR was the only statistically significant risk factor(odds ratio[OR] 6.266, P=0.026) for post-VCUG UTI, while sex, age, and other anomalies of urinary system were not significant. Five post-VCUG UTI cases belonged to prophylactic antibiotics group. Antibiotics use (three groups using antibiotics vs. no-antibiotics group) or addition of antibiotics for VCUG (antibiotics-for-VCUG vs. other groups) did not have any effect on prevention of post-VCUG UTI. Conclusion : The risk factor for post-VCUG UTI was high-grade VUR. Antibiotics use did not prevent post-VCUG UTI in this study.