‘Magnetic piston \ 
H~ with SS sheath j 
) ~~ Motion - sensing 
coll 
Loading springs 
Copper damping ring 
“with SS sheath bellows 
Actuating 
fa ~~ Spring loading 
adjustment 
: “Stem sealing bellows ~~~ Ve 
Ni Helical suspension | So a cee ee 
A} “/ springs 
sary. ff (“ZAK 
tee 
A, ax 
Y RG | : 
F Secondary packing 
N a 
S 'Backseating stem._ ~ 
High level -~ WY ! —~~ Leak detecting tap 
tap N : 
PA i Bellows seal weld-——-~ 
Y fy } t ‘ 
eee ey Y fy ‘ 
OF Faas Ss ; - Seal bellows 
inches Y) o1.2 3 : 
g Displacer : inches : 
Y | : -—- 347 stainless steel 
ff as , 
co ee ee ~—— Stellite No.6 plug | 
FIG. 4. Displacement-type pressurizer-level transmitter 
side the main reactor tank. The in- 
struments were located in these 5-ft- 
diameter 15-ft-long vertical tanks to 
avoid opening the main tank to replace 
instruments, to provide a location for 
instrument components which could 
not be readily protected from the 
water-flooding of the main tank during 
remote maintenance operations, and to 
minimize radiation exposure. How- 
ever, the cubicles are sealed and 
shielded to the same requirements as 
the reactor tank. 
The cell air monitors, which will pro- 
vide an alarm in case of a leak of radio- 
active vapor from the reactor system, 
are installed in one of these instrument 
cubicles. Cell air is circulated through 
a 2-in. pipe from the reactor tank, past 
the enclosed monitors, and then back 
to the cell. The blower is sized so that 
only 5 sec is required for cell air to 
reach the radiation monitors. 
The neutron-sensing elements that 
supply signals to the radiation meter- 
ing instruments are located in two 
5-in.-diameter and two 3-in.-diameter 
aluminum tube ‘‘thimbles.’’ These 
are, in turn, located in a 30-in.-diam- 
eter cylinder-26 ft long, which slopes 
diagonally down from just outside the 
main control room through the 5-ft- 
28 
a ke 
FIG. 5. 
thick sand-and-water radiation shield 
into the main reactor cell. The cham- 
ber ‘‘thimbles” are filled with water 
for shielding and for ready withdrawal 
or positioning. The 30-in. cylinder is 
filled with lead shot and water to re- 
duce the gamma irradiation of the neu- 
tron-sensing elements. 
Design Features 
Interesting design features of the in- 
strumentation and controls system in- 
clude the following: 
(a) Key transmitters are duplicated. 
Signals from electrical transmitters are 
converted to 3- to 15-psi pneumatic 
signals by transducers. The output 
of the unit not controlling is displayed 
on an adjacent receiver gage. A valve 
allows either signal to be fed into 
the controller. Plug-in pneumatic re- 
corders and controllers are used, and 
an air switch allows the loop to be 
manually controlled while the control- 
ler is being replaced. Pneumatic trans- 
mitters are used in control loops affect- 
ing plant safety because an inexpensive, 
reliable emergency control air system, 
in the event of power or compressor 
failure, is provided by nitrogen cylin- 
ders. The supply is adequate for an 
orderly shutdown. 
Letdown valve. 
Action shown is air to open 
(b) A 48-v d-c supply from batteries 
is used for control-circuit power and 
for the operation of key pilot solenoid 
valves controlling the air to critical 
valves. 
(ec) During power operation a nomi- 
nal 300-kva turbine-generator operated 
by reactor steam will be used to pro- 
vide current for sustained operation. 
(d) The critical dump circuit and 
pilot solenoid valves may be checked 
during operation by atest panel. Sole- 
noid valves in this circuit are also dup- 
licated. Ifa bona-fide dump signal oc- 
curs during this test, the test signals 
are overridden. 
(e) All electrical and thermocouple 
leads are insulated with inorganic in- 
sulations, such as, ‘‘Fiberglas,”’ mag- 
nesium oxide, and porcelain to resist 
the deteriorating radiation effects. 
Nuclear Instrumentation 
Nuclear instrumentation in HRT 
is relatively conventional, consisting of 
monitors for process leaks and general 
area radioactivity as well as neutron 
level in the core. 
The gamma monitors for detecting 
process leaks, consist of a simple one- 
tube, three-decade logarithmic ampli- 
fier sealed within the chamber head 
