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research-article

MICRO-POROUS COATINGS AND ENHANCED CHF FOR DOWNWARD FACING BOILING DURING PASSIVE EMERGENCY REACTOR COOLING

[+] Author and Article Information
Albert E. Segall

The Pennsylvania State University University Park, PA 16803 USA
aesegall@psu.edu

Faruk A. Sohag

The Pennsylvania State University University Park, PA 16803 USA
fahmed.buet@gmail.com

Faith R. Beck

The Pennsylvania State University University Park, PA 16803 USA
frb115@psu.edu

Lokanath Mohanta

The Pennsylvania State University University Park, PA 16803 USA
lxm971@psu.edu

Dr. Fan-Bill Cheung

The Pennsylvania State University University Park, PA 16803 USA
fxc4@psu.edu

Timothy J. Eden

The Pennsylvania State University University Park, PA 16803 USA
tje1@arl.psu.edu

John Potter

The Pennsylvania State University University Park, PA 16803 USA
Jkp6@psu.edu

1Corresponding author.

ASME doi:10.1115/1.4037001 History: Received November 09, 2016; Revised June 01, 2017

Abstract

During a Reaction Initiated Accident (RIA) or Loss of Coolant Accident (LOCA), passive external-cooling of the reactor lower head is a viable approach for the in-vessel retention of Corium; while this concept can certainly be applied to new constructions, it may also be viable for operational systems with existing cavities below the reactor. However, a boiling crisis will inevitably develop on the reactor lower head owing to the occurrence of Critical Heat Flux or CHF that could reduce the decay heat removal capability as the vapor phase impedes continuous boiling. Fortunately, this effect can be minimized for both new and existing reactors through the use of a Cold-Spray delivered, micro-porous coating that facilitates the formation of vapor micro-jets from the reactor surface. The micro-porous coatings were created by first spraying a binary mixture with the sacrificial material then removed via etching. Subsequent quenching experiments on uncoated and coated hemispherical surfaces showed that local CHF values for the coated vessel were consistently higher relative to the bare surface. Moreover, it was observed for both coated and uncoated surfaces that the local rate of boiling and local CHF limit varied appreciably along the outer surface. Nevertheless, the results of this intriguing study clearly show that the use of Cold Spray coatings could enhance the local CHF limit for downward facing boiling by more than 88%. Moreover, the Cold-Spray process is amenable to coating the lower heads of operating reactors.

Copyright (c) 2017 by ASME
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