United States Nuclear Regulatory Commission - Protecting People and the Environment

Assessment of the Wall Film Condensation Model with Non-condensable Gas in RELAP5 and TRACE for Vertical Tube and Plate Geometries (NUREG/IA-0491)

On this page:

Download complete document

Publication Information

Manuscript Completed: August 2017
Date Published: February 2019

Prepared by:
Jehee Lee*, Chi-Jin Choi*, Hyoung Kyu Cho*, Kyung Won Lee**, Min Ki Cho**

*Department of Nuclear Engineering,
Seoul National University
1 Gwanak-ro, Gwanak-gu, Seoul, 08826, Republic of Korea

**Korea Institute of Nuclear Safety
62 Gwahak-ro, Yuseong-gu, Daejeon 34142, Republic of Korea

K. Tien, NRC Project Manager

Division of Systems Analysis
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

Prepared as part of:
The Agreement on Research Participation and Technical Exchange
Under the Thermal-Hydraulic Code Applications and Maintenance Program (CAMP)

Published by:
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

Availability Notice


In the interest of providing increased power supply, available passive safety features such as Passive Containment Cooling System (PCCS) and Passive Auxiliary Feedwater System (PAFS) have been adopted for use in advanced nuclear power reactors. The accurate prediction of condensation heat transfer in these systems has been emphasized to assure the safety of nuclear reactors. Especially in the PCCS, condensation occurs in the presence of non-condensable gases that concentrate on the condenser wall. The concentrated gases reduce the steam partial pressure and degrade the heat transfer rate.

In order to predict the condensation rate under this condition, RELAP5 (which is generally used for simulation of best-estimate transients in light water reactor coolant systems) uses the Colburn-Hougen model. Recently, it was found that an error was included in the condensation mass flux model of RELAP5, and the source code of the model was corrected. Next, it was necessary to assess the predictive capability of the corrected model in relation to existing experimental results and in relation to results predicted using another code.

In this study, seven condensation experiments were simulated using RELAP5 and TRACE. These were used to describe condensation on the inner wall of the channel in the presence of non-condensable gases. Then, the predicted heat flux and heat transfer coefficient from both codes were compared with experimental results to evaluate the condensation models.

Page Last Reviewed/Updated Friday, February 15, 2019