Hyun Sik Park

A condensation experiment in the presence of noncondensables in a vertical tube of a passive containment cooling system and its assessment with RELAP5/MOD3.2

A condensation experiment in the presence of non-condensable gas in a vertical tube of the passive containment cooling system of the CP-1300 is performed. The experimental results show that the heat transfer coefficients (HTCs) increase as the inlet air mass fraction decreases and the inlet saturated steam temperature decreases. However the dependence of the inlet mixture Reynolds number on the HTC is small for the operating range. An empirical correlation is developed, and its predictions are compared with experimental data to show good agreement with the standard deviation of 22.3%. The experimental HTCs are also compared with the predictions from the default and the alternative models used in RELAP5/MOD3.2. The experimental apparatus is modeled with two wall-film condensation models in RELAP5/MOD3.2 and the present model, and simulations are performed for several subtests to be compared with the experimental results. Overall, the simulation results show that the default model of RELAP5/MOD3.2 underpredicts the HTCs, and the alternative model over-predicts them, while the present model predicts them well throughout the condensing tube.

Simulation Capability of the ATLAS Facility for Major Design-Basis Accidents

A thermal-hydraulic integral-effect test facility [advanced thermal-hydraulic test loop for accident simulation (ATLAS)] is being constructed at the Korea Atomic Energy Research Institute. The ATLAS is a one-half-reduced-height and 1/288-volume-scaled test facility based on the design features of the APR1400, an evolutionary pressurized water reactor developed by the Korean industry. The simulation capability of the ATLAS for major design-basis accidents (DBAs), including a large-break loss-of-coolant accident and direct vessel injection line-break and main-steam-line-break accidents, is evaluated by the best-estimate system code MARS with the same control logics, transient scenarios, and nodalization scheme. The validity of the applied scaling law and the thermal-hydraulic similarity between the ATLAS and the APR1400 for the major DBAs are assessed. It is confirmed that the ATLAS can maintain an overall similarity with the reference plant APR1400 for the major DBAs considered in the study. However, depending on the accident scenarios, there are some inconsistencies in certain thermal-hydraulic parameters, such as cladding temperature, subcooling at the lower plenum of the core, break flow rate, core and downcomer water level, and secondary pressure. The causes of the inconsistencies are carefully investigated by considering the detailed design features of the ATLAS. It is found that the inconsistencies are mainly due to the reduced power effect and the increased stored energy in the structure. The similarity analysis was successful in obtaining a greater insight into the unique design features of the ATLAS and would be used for developing optimized experimental procedures and control logics.

Assessment and Improvement of Condensation Models in RELAP5/MOD3.2

The condensation models of the standard RELAP5/ MOD3.2 code are assessed and improved based on a database that is constructed from previous experimental data of various condensation conditions. The RELAP5/MOD3.2 default model of laminar film condensation does not give any reliable predictions, and the alternative model always predicts values higher than those of the experimental data. Therefore, a new correlation based on the experimental data of various operating ranges is needed. The Shah correlation, which is used to calculate the turbulent film condensation heat transfer coefficients in the standard RELAP5/MOD3.2, gives good agreement with the database except for Kuhn s experimental data. The RELAP5/MOD3.2 horizontally stratified condensation model overpredicts both cocurrent and countercurrent experimental data. The Kim correlation predicts the database relatively well compared with that of RELAP5/MOD3.2.

Effects of Break Size on Direct Vessel Injection Line Break Accidents of the ATLAS

Abstract The direct vessel injection (DVI)-adopted power plant APR1400 considers a DVI line break among the analyzed small-break loss-of-coolant accidents in safety analysis. The first-ever integral effects test database for various DVI line break sizes from 5% to 100% was established with the Korea Atomic Energy Research Institute’s Advanced Thermal-Hydraulic Test Loop for Accident Simulation (ATLAS) test facility. This database enhances our physical understanding of the major thermal-hydraulic behaviors of the APR1400 during DVI line break accidents, and it can also be used to examine the prediction capabilities and identify any deficiencies in the existing best-estimate safety analysis codes. Effects of the break size were experimentally investigated, and the best-estimated MARS code was assessed against the experimental database. On the whole, the prediction of the MARS code shows a good agreement with the measured data. However, the code predicted a higher core level than the data just before a loop seal clearing occurs, and it also produced a more rapid decrease in the downcomer water level than the data. These disagreements are the expected consequence of uncertainties in predicting countercurrent flow or condensation phenomena in a downcomer region. The present integral effects test data will be used to support the present conservative safety analysis methodology and to develop a new best-estimate safety analysis methodology on the DVI line break accidents of the APR1400.

DEVELOPMENT OF A WALL-TO-FLUID HEAT TRANSFER PACKAGE FOR THE SPACE CODE

The SPACE code that is based on a multi-dimensional two-fluid, three-field model is under development for licensing purposes of pressurized water reactors in Korea. Among the participating research and industrial organizations, KAERI is in charge of developing the physical models and correlation packages for the constitutive equations. This paper introduces a developed wall-tofluid heat transfer package for the SPACE code. The wall-to-fluid heat transfer package consists of twelve heat transfer subregions. For each sub-region, the models in the existing safety analysis codes and the leading models in literature have been peer reviewed in order to determine the best models which can easily be applicable to the SPACE code. Hence a wall-to-fluid heat transfer region selection map has been developed according to the non-condensable gas quality, void fraction, degree of subcooling, and wall temperature. Furthermore, a partitioning methodology which can take into account the split heat flux to the continuous liquid, entrained droplet, and vapor fields is proposed to comply fully with the three-field formulation of the SPACE code. The developed wall-to-fluid heat transfer package has been pre-tested by varying the independent parameters within the application range of the selected correlations. The smoothness between two adjacent heat transfer regimes has also been investigated. More detailed verification work on the developed wall-to-fluid heat transfer package will be carried out when the coupling of a hydraulic solver with the constitutive equations is brought to completion.

A SUMMARY OF 50 th OECD/NEA/CSNI INTERNATIONAL STANDARD PROBLEM EXERCISE (ISP-50)

This paper describes a summary of final prediction results by system-scale safety analysis codes during the OECD/NEA/CSNI ISP-50 exercise, targeting a 50% Direct Vessel Injection (DVI) line break integral effect test performed with the Advanced Thermal-Hydraulic Test Loop for Accident Simulation (ATLAS). This ISP-50 exercise has been performed in two consecutive phases: “blind” and “open” phases. Quantitative comparisons were performed using the Fast Fourier Transform Based Method (FFTBM) to compare the overall accuracy of the collected calculations. Great user effects resulting from the combination of the possible reasons were found in the blind phase, confirming that user effect is still one of the major issues in connection with the system thermal-hydraulic code application. Open calculations showed better prediction accuracy than the blind calculations in terms of average amplitude (AA) value. A total of nineteen organizations from eleven countries participated in this ISP-50 program and eight leading thermal-hydraulic system analysis codes were used: APROS, ATHLET, CATHARE, KORSAR, MARS-KS, RELAP5/MOD3.3, TECH-M-97, and TRACE.

An Integral Effect Test on the Reflood Period of a Large-Break LOCA for the APR1400 Using ATLAS

A thermal-hydraulic integral effect test facility, Advanced Thermal-Hydraulic Test Loop for Accident Simulation (ATLAS), has been constructed at the Korea Atomic Energy Research Institute. It is a 1/2-reduced-height and 1/288-volume-scaled test facility based on the design features of APR1400, an evolutionary pressurized water reactor developed by the Korean industry. ATLAS was used to perform a set of integral effect tests on the reflood period of a large-break loss-of-coolant accident (LBLOCA) after intensive performance tests had been conducted to verify ATLAS’s operational performance and controllability for major thermal-hydraulic components. The present LB-CL-09 test is one of the integral effect reflood tests for investigating the thermal-hydraulic characteristics during an entire reflood period that can be used to provide reliable data to help validate the LBLOCA analysis methodology for APR1400. The main objective of the present test is to identify the major thermal-hydraulic characteristics such as the direct emergency core coolant (ECC) bypass, downcomer boiling, and core cooling behavior during the reflood phase of an LBLOCA for APR1400 under conditions where the downcomer region interacts with the reactor core region and the heat could be transferred through the steam generator. The initial and boundary conditions were obtained by applying scaling ratios to the MARS simulation results. The decay heat and the ECC flow rate from the safety injection tank were simulated from the start of the reflood period. The ECC flow rate from the safety injection pump was 0.32 kg/s. The system pressure was fixed at ~0.1 MPa, and the initial outer-wall temperature was determined to be 205°C. The experimental results showed the typical thermal-hydraulic trends expected to occur during the reflood phase of the LBLOCA scenario.

Health-Related Quality of Life, Perceived Social Support, and Depression in Disease-Free Survivors Who Underwent Curative Surgery Only for Prostate, Kidney and Bladder Cancer: Comparison among Survivors and with the General Population

Purpose The purpose of this study was to compare health-related quality of life (HRQoL) of disease-free prostate (PC), kidney (KC), and bladder cancer (BC) survivors with that of the general population. Materials and Methods Our study included 331 urological cancer (UC) survivors (114 PC, 108 KC, and 109 BC) aged ≥ 50 years disease-free for at least 1 year after surgery. The control group included 1,177 subjects without a history of cancer. The HRQoL was assessed using the European Organization for Research and Treatment of Cancer QLQ-C30, the Duke-UNC Functional Social Support Questionnaire, and the Patient Health Questionnaire-9. Results There was no significant difference between the groups in terms of any of the functioning sub-scales and symptoms, except significantly lower social functioning observed in BC survivors than that observed in KC survivors. Although the three groups of UC survivors showed essentially similar functioning sub-scales and symptoms when compared to the general population, PC and BC survivors showed significantly lower social functioning and a lower appetite than that observed in controls. KC survivors showed lower physical functioning, as well as higher pain and dyspnea. Although all three groups of UC survivors reported higher financial difficulties, they also reported higher perceived social support than that reported by the non-cancer control group. No statistically significant difference was observed in terms of depressive symptoms between each group of UC survivors and the general population. Conclusion Disease-free survivors of the three major types of UCs showed generally similar HRQoL compared to the general population, as well as compared to each other.

Post-Test Analysis of an Integral Effect Reflood Test for an APR1400 Large-Break LOCA Scenario

Post-test analysis was performed on an integral effect reflood test, the ATLAS Test No. 9, for an APR1400 Large-Break LOCA (LBLOCA) scenario by using the MARS code. Integral effect tests on the reflood period of a large break LOCA were performed by using the ATLAS facility to help understand the thermal-hydraulic phenomena during the reflood period of a large-break LOCA for APR1400 and for resolving the current safety issues for the APR1400 licensing on the downcomer boiling phenomenon. The present ATLAS Test No. 9 is one of the integral effect reflood tests for investigating the thermal-hydraulic characteristics during an entire reflood period to provide reliable data to help validate the LBLOCA analysis methodology for APR1400.Copyright