Instrumentation 
and Controls 
for HRT 
Here's a description of the over-all system for 
control of the HRT as well as the components 
that make it up. In particular several 
temperature, level, and pressure transmitters 
are described in detail 
By D. S. TOOMB, Jr. 
Oak Ridge National Laboratory, Oak Ridge, Tennessee 
eaters | 
FIG. 1. Basic flow sheet for HRT. Heavy lines show fuel flow 
26 
THE INHERENT STABILITY of the aque- 
ous homogeneous reactor system* elim- 
inates the need for control or safety 
rods. Control functions are performed 
by valves which regulate the fuel con- 
centration and the rate of steam re- 
moval from the heat exchangers. 
The instrumentation and controls 
system for the Homogeneous Reactor 
Test (1-3), the second experimental 
aqueous homogeneous reactor to be 
constructed under the AEC program 
for the evaluation of power reactors, 
was heavily influenced by the need for 
extreme reliability. All components 
exposed to the process fluid are abso- 
lutely leaktight and resistant to high 
levels of nuclear radiation. Special 
liquid-level transmitters have been de- 
veloped for use under the reactor op- 
erating conditions, and all-welded con- 
struction was used broadly. 
Basic Flow Sheet 
Figure 1 indicates the basic flow 
sheet for HRT. Heat is generated in 
the 32-in.-diameter core vessel by fis- 
sion. Steam from the heat exchanger 
goes to a turbine generator (or to an 
air-cooled condenser at power levels 
above the rating of the turbine). Also 
shown are the circulating pump that 
circulates the fuel at 400 gpm; and an 
electrically heated pressurizer that pre- 
vents boiling in the circulating stream 
and whose vapor space provides a 
surge volume to damp _ reactivity 
excursions. 
Also shown is a secondary stream 
consisting of gas and entrained liquid 
removed from the nrain stream by the 
gas separator; this gas-liquid mixture 
flows to the low-pressure dump tanks 
and gas recombiners through the let- 
down valve. The liquid loss from the 
high-pressure system is made up by 
continuous feed-pump operation. 
The blanket flow system is identical 
but circulates a different fluid (heavy 
water at 230 gpm during initial opera- 
tion, fertile material later). 
The 60-in.-i.d. blanket vessel is de- 
signed to withstand the 2,000-psi op- 
erating pressure. But the 5{¢-in.- 
* A homogeneous nuclear reactor is one 
in which the fuel material is evenly dis- 
persed throughout the moderator as dif- 
ferentiated from reactors using solid fuel 
elements. Aqueous homogeneous reactors 
are desirable because the fluid state of the 
fuel and the properties of light and heavy 
water as a moderator permit the design of a 
system with high power density and low 
fuel inventory. 
