Fi 
0.008-in. 
sensing be 
jexure tube 
Hows 
Pressure = 
tops F— 
—" 
FIG. 7. Pneumatic-transmission differ- 
ential-pressure cell employing a bellows 
sensing element 
rates a two-section, three-ply stainless- 
steel sealing bellows, an integral forged 
347 stainless-steel seat, and a stellite 
No. 6 plug. The mechanically formed 
bellows plies are each 0.0085-in. thick. 
The valve operator is all metallic so as 
to be radiation resistant; it uses a bel- 
lows to produce the linear shaft motion. 
The shaft is also sealed with a bellows 
to prevent air leakage into the evacu- 
ated reactor equipment cell. 
The valve,* is rated for 2,500-psi 
service with the flow introduced under 
the seat; however, the downstream 
pressure is limited to 500 psi by the 
bellows seal. The valve strokes !9 in. 
and has a C, of 0.1. The secondary 
packing seal is graphited asbestos. 
The reversible operatort has a 50-in.? 
effective area and is rated for a maxi- 
mum of 60 psi air. 
The dump valve is a similar but 
larger valvef designed for on-off service. 
This valve strokes 5g in. and has a C, 
of 10. The trim material and sealing 
bellows are the same as those used in 
the letdown valve. The larger oper- 
ator has a two-ply 321 stainless-steel 
bellows with an effective area of 68 in.* 
and is rated for 80-psi actuating air 
pressure. 
The absolute-pressure transmitter 
shown in Fig. 6 is a weld-sealed electric- 
transmission type§] with an operating 
range of 0-300 in. of water but is capa- 
ble of withstanding overranging to 
2,000 psi. Overrange protection is pro- 
vided by the convoluted diaphragm 
backup flange, which limits the dia- 
* Supplied by The Fulton-Sylphon Divi- 
sion, Robertshaw-Fulton Controls Co. 
t+ Supplied by The Annin Co. 
t Valve and operator were supplied by 
The Fulton-Sylphon Division. 
{These units were supplied by 
Foxboro Co. 
The 
30 
phragm motion. Such instruments 
may be overranged from dumps, when 
the contents of the high-pressure sys- 
tem are rapidly emptied into the stor- 
age tanks. Specifications include 
140° F operating temperature, 1 mv/v 
output, 3% accuracy, and 347 stainless 
steel in contact with process fluids. 
Differential-pressure cells with similar 
design are also utilized. 
Figure 7 illustrates a 3- to 15-psi out- 
put pneumatic-transmission differen- 
tial-pressure cell§ which uses a bellows 
sensing element and an all-welded flex- 
ure tube seal. The range of the cell is 
+50 psi with an overrange rating of 
+100 psi. The housing design pres- 
sure of the cell, is 4,000 psi. The unit 
is completely weld-sealed and fabri- 
cated from 347 stainless steel. 
Float switches of the type used for 
high or low liquid-level alarm** also 
have all-weld seals. The mercury 
switch is tripped by the action of the 
moving magnetic piston on a perma- 
nent magnet. All parts exposed to the 
process fluid or its vapors are stainless 
steel. The control is rated for 600-psi 
service. 
Another pneumatic pressure trans- 
mitterft has a range of 0-3,000 psi. 
Specifications provide for overrange to 
3,750 psig, operating temperature of 
140° F, hysteresis of +15 psi, sensi- 
tivity of +3 psi, and weld-sealed 347 
stainless steel element. 
Interlocks 
Extensive protective interlocking of 
the controls circuits is provided to pre- 
vent unsafe operating conditions. 
However, flexibility of operation is pro- 
vided by the ‘‘jumper board” to facili- 
tate special experimental operating 
conditions. 
Examples of interlocked systems in- 
clude the following: 
Pumping of fuel instead of conden- 
sate to the reactor core is prevented by 
several interlocks that keep the fuel- 
addition valve closed until the core is 
full of condensate and has been heated 
to 200° C. This prevents power and 
consequent pressure surges. 
For the same reason the fuel pump 
is started in reverse to provide a low 
flow rate as protection against pumping 
cold solution too rapidly from the heat 
exchanger into the core. 
§ Supplied by The Foxboro Co. 
** Supplied by Magnetrol Inc. 
+t This transmitter was supplied com- 
plete by The Taylor Instrument Companies. 
To avoid dangerous thermal stresses, 
the control circuits do not permit the 
pumping of cold feed water into the 
heat exchangers until the level is above 
50%. 
To give smooth startup, the fuel 
injection pump can only run at half 
speed up to a temperature of 240° C. 
The fuel feed valve will be closed and 
the concentration in the fuel system 
will be lowered by injecting condensate 
if the core outlet temperature becomes 
excessive, if the circulating pump stops, 
or if the power level exceeds normal. 
The contents of the high-pressure 
systems will be automatically emptied 
to the low-pressure storage tanks 
through the ‘‘dump” valves on a signal 
of extremely high pressure, or a radi- 
ation leak into the steam system. Dif- 
ferential-pressure control between the 
core and blanket systems during this 
dump is by off-on control of valves 
from a differential-pressure signal. 
Inventory Systems 
For obtaining an accurate inventory 
of the fuel and moderator solutions, 
as required for accountability purposes 
with special nuclear materials, the stor- 
age and condensate tanks are weighed 
with pneumatic weigh cells. This was 
found to be the only feasible method of 
measuring the liquid in the 16-ft-long 
15-in.-diameter horizontal storage 
tanks necessary because of criticality 
and space considerations. A  pneu- 
matic system was selected primarily 
because taring can be done remotely 
with balancing air pressures and com- 
ponents are less susceptible to radiation 
damage. 
Piping to the tanks is kept flexible, 
to compensate for the varying loads 
which result from thermal expansion, 
by confining piping runs to horizontal 
planes with “L”’ and ‘‘U” bends in the 
lines. 
* * * 
The author wishes to acknowledge the 
following Oak Ridge National Laboratory 
instrumentation and control personnel whose 
work is reported in this paper—J. N. Baird, 
M. C. Becker, A. M. Billings, J. R. Brown, 
J.C. Gundlach, R. L. Moore, W. P. Walker 
(now at the University of Virginia), E. 
Vincens, and K. W. West. 
Dean L. R. Quarles of the University of 
Virginia has served as an invaluable con- 
sultant. 
BIBLIOGRAPHY 
1. S. E. Beall, C. E. Winters, Chem. Eng. Prog. 
50, No. 5, 256 (1954) 
. W.R. Gall, Mech. Eng., 575 (1955) 
. S.E. Beall, J. A. Swartout. The Homogeneous 
Reactor Test in ‘‘Proceedings of the Inter- 
national Conference on Peaceful Uses of 
Atomic Energy, vol. 3, p. 263 (United Nations, 
New York, 1956) 
we 
