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Technical Papers

Experimental Investigation of Single- and Two-Phase Diversion Cross Flow in Simulated Subchannels of a Natural-Circulation Pressure Tube–Type BWR

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Pages 175-186 | Received 01 May 2017, Accepted 03 Jun 2017, Published online: 09 Aug 2017
 

Abstract

The Advanced Heavy Water Reactor (AHWR) is a vertical pressure tube–type, heavy water–moderated, and boiling light water–cooled natural-circulation–based reactor. The fuel bundle of AHWR contains 54 fuel rods arranged in three concentric rings of 12, 18, and 24 fuel rods. This fuel bundle is divided into a number of imaginary interacting flow passages called subchannels. Transition from a single-phase to a two-phase flow condition occurs in the reactor rod bundle with an increase in power. Predicting the thermal margin of the reactor has necessitated determining the diversion cross flow of coolant among these subchannels under two-phase flow. Thus, it is vital to evaluate cross flow between subchannels of the AHWR rod bundle. In this paper, experiments were carried out to investigate the diversion cross-flow phenomena for single- and two-phase flow in the simulated subchannels of the reactor. The size of the rod and the pitch in the test were the same as that of the actual rod bundle in the prototype. The cross-flow tests were carried out at atmospheric condition without adding heat. In addition, the capability of the existing correlation is also checked to predict the cross-flow resistance coefficient, and it is found that none of these models accurately predict the measured cross-flow resistance coefficient for the AHWR rod bundle. In view of this, a new model applicable to AHWR has been presented that predicts the cross-flow resistance coefficient quite accurately.

Nomenclature

A=

= flow area (m2)

Dh=

= hydraulic diameter (m)

d=

= rod diameter (m)

f=

= friction factor

G=

= mass flux (kg/m2·s)

g=

= acceleration due to gravity (m/s2)

J=

= superficial velocity

K=

= transverse resistance coefficient

P=

= pressure

Re=

= Reynolds number

R=

= rotameter

S=

= gap (m)

V=

= velocity

=

Greek

δ=

= centroidal distance between subchannel (m)

ρ=

= density (kg/m3)

ν=

= kinematic viscosity (m2/s)

=

Subscript

cal=

= calculated

dc=

= diversion cross flow

don=

= donor subchannel

exp=

= experimental

g=

= gas

i,j=

= subchannel identifier

l=

= liquid

rec=

= recipient subchannel

sp=

= single phase

tp=

= two phase

t=

= total

1, 2, 3=

= subchannel identifier

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