The improvement of the interfacial drag model in RELAP5/MOD3.3 to simulate downcomer boiling phenomena in APR1400
Conference
·
OSTI ID:21016377
- Nuclear Environmental Technology Institute, Korea Hydro and Nuclear Power Co., Ltd (KHNP) P.O.Box 149, Yuseong, Daejeon, 305-600 (Korea, Republic of)
In late reflood phase of LBLOCA, the injected water flow-rate is small compared to those in refill and early reflood phases due to the termination of large cooling water source, that is, the Safety Injection Tanks (SITs). At this situation, the water in downcomer could be vaporized near the reactor vessel wall surface having stored energy. The technical issue is if this local boiling could be extended to the bulk boiling, so called 'Downcomer Boiling'. Some system codes (e.g. RELAP, TRACE) predict this generated steam prevents the penetration of safety injection water into core and eventually degrades the core cooling capability. In this concern, separate effect tests on the downcomer boiling phenomena have been performed. When water in downcomer is boiled off by heated wall, interactions between void and liquid become important. Interfacial drag model is one of key factors to handle those phenomena in RELAP5/MOD3.3. So, we assessed several models related to interfacial drag in RELAP5/MOD3.3 code to obtain the most appropriate model using the experiment. EPRI and Bestion correlations are compared to Kataoka-Ishii correlation. Also, we perform the comparison by adopting Blasius model used in TRACE code. In TRACE code, Blasius model is a special interfacial drag model which applied in the downcomer only. Especially, because Bestion correlation is developed for channel having small diameter, we conduct additional assessment by multiplying factor for calibration of hydraulic diameter term within the correlation. As the results of the assessment, the modified Bestion model is most appropriate to simulate the experiments. Finally, we assess CCTF (Cylindrical Core Test Facility) C2-4 test using the improved model to confirm the validity of the developed model. (authors)
- Research Organization:
- American Nuclear Society, 555 North Kensington Avenue, La Grange Park, IL 60526 (United States)
- OSTI ID:
- 21016377
- Country of Publication:
- United States
- Language:
- English
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