Title: Mitigation of Baffle Plate Heat Transfer Effects for the AP1000 and HSP1000

Title: Mitigation of Baffle Plate Heat Transfer Effects for the AP1000 and HSP1000

Sponsor: Westinghouse

Sponsor Advisor: Jeff Dederer, Cranberry , 412-374-3452, Charles Kling, Windsor CT, , 860-731-6604

Description: Following the events that occurred at the Fukushima-Daichi power plant in Japan, there has been significant interest in the development of a high seismic version of the AP1000 nuclear power plant design. Important aspects of such a design include the ability of the plant to place and maintain itself in a safe shutdown condition using only passive systems. Following a high seismic event with a subsequent station blackout condition (loss of offsite and onsite power), it is desirable to have a design which can cope with these conditions for as long as possible without intervention. One critical part of this is the ability to reject heat to the atmosphere from the containment. The Passive Containment Cooling System (PCS) relies on natural convection airflow through an annulus around the containment vessel. There is a baffle plate separating the concrete of the Shield Building from the steel of the CV which also acts as a guide for the airflow. A percentage of the heat generated by the steel CV shell is radiated to the baffle plate and therefore acts as a pre-heater to the incoming airflow in the downcomer area. This phenomenon has a negative effect on heat transfer from the CV to the bulk airflow between the baffle and the steel shell (lower delta T → lower heat transfer). If the amount of heat transferred to the downcomer air from the baffle could be minimized, then colder air would come into contact with the steel CV and greater heat transfer would occur thereby improving the overall coping capability of the plant.

This analysis effort [GOTHIC software] is intended to examine methods of reducing the heat transfer from the baffle to the incoming air. Specifically, the following elements would be part of this effort:

1.  Reviewing current PCS design and airflow paths

2.  Developing an appropriate model to quantify heat transfer from the containment surface to the baffle plate/up flowing air and from the baffle plate to the incoming (down flowing) air in the current design

3.  Brainstorming different methods which could be beneficial in reducing heat transfer to the incoming air

4.  Researching different materials/coatings/geometries to minimize heat transfer to the incoming air

5.  Adjusting the model to test the candidate modification

6.  Compiling analysis data and making comparisons to baseline

7.  Producing a final report of analysis, methods, findings, and recommendations

Westinghouse will provide appropriate design input along with the boundary conditions for the incoming air and the containment surface temperature, based on previous GOTHIC analyses of the containment for the current design.

Objective:. Initially students are to concentrate on 1) understanding the air cooling process for the containment and 2) potential modifications to the baffle plate design to reduce heat transfer to the incoming air. Boundary condition input will be provided based on current GOTHIC analyses as the baseline for the study. Based on the various design modifications they identify, Westinghouse is most interested in the impact on the incoming air. Only if they complete this scope and have additional time would we have them consider how to implement the baffle plate modifications into GOTHIC in order to evaluate the impact on the peak containment pressure.