A jet pump, in combination with a TEMP, is employed to assure safe cooling of a nuclear reactor after shutdown. A TEMP, responsive to the heat from the coolant in the secondary flow path, automatically pumps the withdrawn coolant to a higher pressure and thus higher velocity compared to the main flow. The high velocity coolant is applied as a driver flow for the jet pump which has a main flow chamber located in the main flow circulation pump. Upon nuclear shutdown and loss of power for the main reactor pumping system, the TEMP/jet pump combination continues to boost the coolant flow in the direction it is already circulating. During the decay time for the nuclear reactor, the jet pump keeps running until the coolant temperature drops to a lower and safe temperature. At this lower temperature, the TEMP/jet jump combination ceases its circulation boosting operation. The TEMP/jet pump combination is automatic, self-regulating and provides an emergency pumping system free of moving parts

French, J. R.

English

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NASA CASE NO.	 ^ `l 7 GZ / ^—G' (J {
PRINT FIG.
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programs of the National Aeronautics and Space Administration.
The invention is owned by NASA and is, therefore, available for
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(NASA-Case-NPO-16494- 1-CU) JET PUMP-DRIVE	 N85-29182
SYSTEM FOR NEAT BINOV21 Patent Application
(NASA) 10 p NC A02/MF 401	 CSCL 20D
Unclas
G3/34 15174
,.rr
.SRO-JPL
AWARDS ABSTRACT
Inventor:	 James R. French	 JPL Case No. 16494
NASA Case No. NPO-16494-1-e-41
J&J Case No. JET1-E81
Date: April 1, 1985
Contractor: Jet Propulsion Laboratory
JET.PUMP-DRIVE SYSTEM FOR HEAT REMOVAL
The invention (Fig. 2) does away with the
necessity of moving parts such as a check valve (19,
Fig. 1) in a prior art nuclear reactor cooling system.
A jet pump (23, Fig. 2), in combination with a TEMP (22,
Fig. 22), is employed to assure automatic, self-regulating
and safe cooling of a nuclear reactor after shutdown. A
main flow (26, 27, Fig. 2) exists for a reactor coolant.
A point of withdrawal (25, Fig. l) is provided for a
secondary flow (28, Fig. 2). A TEMP, responsive to the
heat from said coolant in the secondary flow path, auto-
matically pumps said withdrawn coolant to a higher
pressure and thus velocity. The higher velocity is
applied as a driver flow (232A) for the jet pump (23)
which has a main flow chamber located in the main flow
circulation loop. Upon nuclear shutdown and loss of
power for the main reactor pumping system, the TEMP/jet
pump combination (22, 23) continues to boost the liquid
coolant flow in the direction it is already circulating.
During the decay time for the nuclear reactor, the jet
pump keeps running until the coolant temperature drops
to a lower and safe temperature where the heat is no
longer a problem.
f
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Serial N0,__&_3_44,_7X
Filing Date
	 _'
Coniract No.
	 NAS7.918
Contractor
	 Caltecll(JPL
Pasadena	 CA.	 91109(City)	 (State)	 (Zip)
	TO REACTOR	 TO REACTOR
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V ^CK	 TEMP	 TEMP
	
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COOLING	 COOLING	 j
PUMP	 j	 PUMP
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FROM	 FROM
	
REACTOR	 REACTOR
	
FI G. I	 FIG. 2	 a
PRIOR ART	 7 39j 7S Q	 ill k)
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PATENT
Serial No,_?Cq. f, .7P
JPL Case No.:
	
16494
NASA Case No.: NPO-16494-1-^1/ Co'•.r, fdo, 	 NAS7.918
J&J Case No.:	 JET1-EBl
	 CCJItech(JPL
aCA,	 91109 (State) 	 (tip)
JET PUMP-DRIVE SYSTEM FOR HEAT REMOVAL
BACKGROUND OF THE INVENTION
1. origin of the Invention
The invention described herein was made in the
performance of work under a NASA Contract and is subject
to the provisions of Public Law 96-517 (35 USC 202) in
which the contractor has elected not to retain title.
2. Field of the Invention
An emergency or normal shutdown of any high-
temperaturized nuclear reactor creates a need for a
system to remove excessive heat. During the course of
their operation, such nuclear reactors produce radio-
active materials which decay and produce heat for a
period of time after reactor shutdown. To prevent
damage or destruction to the reactor and associated
systems, the liquid metal coolant must continue to
circulate until a safe temperature' is'achieved. After
the reactor shutdown, there may ! not- be enough power for
the main pumping system to continue operation.
In accordance with this invention, a parallel
auxiliary Thermoelertric Electromagnetic Pump (TEMP), in
combination with a jet pump, is used as a self-starting
and self-regulating auxiliary pumping system. Whereas
the conventional prior art approach requires moving parts
such as check or similar valves, the invention, in a pre-
ferred embodiment, does not employ any moving parts.
,
r
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Moving parts, such as check valves, are notoriously
2 unreliable when subjected to high-temperature and held
3 in one position (open or closed) for long periods. This
4 unreliability is especially acute when a highly corro-
5 sive hot liquid metal coolant is involved as the cooling
6 medium for the system. Furthermore, if a check valve
7 fails in an open position, the system reactor may be
8 damaged or destroyed.
9
	
A parallel TEMP, in this invention, is used to
10 reinject a secondary stream of metal coolant into the
11 main coolant stream. The reinjection, acting as a drive
12 fluid for a jet pump and using the principal. of momentum
13 exchange, induces a circulation of the main fluid. Proper
14 arrangement and positioning of the jet pump, with respect
15 to flow withdrawal and reinjection, prevents backflow.
16
17
	 3. Background Discussion
18
	
TEMPS have been used in combination with check
19 valves in order to prevent backflow during continued
20 circulation after nuclear reactor shutdown. The TEMP
21 relies upon the excess heat in the nuclear reactor's
22 liquid coolant to keep circulation going until the
23 reactor temperature drops to a safe limit.
24
	
When a check valve of the prior art fails in
25 an open condition, which may happen in liquid metal
26 systems, the backflow impedes or..•'prevents circulation
27 and the system may be' damaged..or, destroyed. 	 These
28 moving-pars: check valves are unreiiable in liquid metal
29 circulation systems.
30
31 SUMMARY OF THE INVENTION
32
	
The invention does away with the necessity of
33 a check valve in a nuclear reactor cooling system.
34 Instead, in this invention a jet pump, in combination
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with a TEMP, is employed to assure safe cooling of a
nuclear reactor after shutdown.
The invention comprises a main flow for
reactor coolant together with a point of withdrawal for
a secondary flow. A TEMP, responsive to the heat from
said coolant in the secondary flow path, automatically
pumps said withdrawn coolant to a higher pressure. The
higher pressure is applied as a driver flow for a jet
pump which has a main flow chamber located in the main
flow circulation loop. Upon nuclear shutdown and loss
of power for the main reactor pumping system, the
TEMP/jet pump combination continues to boost the liquid
coolant flow in the direction it is already circulating.
During the decay time for the nuclear reactor, the jet
pump keeps running until the coolant temperature drops
to a lower and safe temperature where the heat is no
longer a problem. At this lower temperature, the
TEMP/jet pump combination ceases its circulation
boosting operation.
When the nuclear reactor is restarted and the
coolant again exceeds the lower temperature setting, the
TEMP/jet pump automatically resumes operation. Although
continually operative while the reactor is operational,
the TEMP/jet pump efficiency loss is small. Thus, a
highly reliable protection system is provided by this
invention.
BRIEF SUMMARY OF THE DRAWINGS
Figure 1 is a known prior art TEMP/check valve
system; and
Figure 2 depicts the TEMP/jet pump combination
for coolant flow in accordance with this invention.
-4-
1 DETAILED DESCRIPTION OF THE DRAWINGS
2
	
The known prior art, is depicted in Figure 1.
3 A liquid metal coolant circulation system 10 employs a
4 primary cooling pump 12 which takes the hot liquid metal
5 coolant 14 from the reactor and feeds it into a main
6 flow path 15 and an auxiliary flow path 18. A thermo-
7 electric electromagnetic pump (TEMP) 16 is connected in
8' the parallel path and is responsive to the heat for
9 auxiliary pumping of the coolant. A check valve 19 is
10 located in the main flow path 15. When closed, valve 19
11 prevents backflow.
12
	 When the reactor (not shown) shuts down, it is
13 imperative that coolant flow be maintained until the
14 excess temperature has been removed from the reactor.
15 The reactor will not cool to a safe level when the power
16 for the primary cooling pump 12 is lost.
17
	 A particularly difficult problem faced by the
18 prior art of Figure 1 is presented when the check
19
	
valve 19 fails. If the valve fails in an open position,
20 the flow will simply go around the loop and coolant in
21 the reactor will stagnate, which will damage or destroy
22
	 the reactor. If the valve fails in a closed condition,
23
	 the coolant cannot circulate.	 Such failure of check
24
	
valves is a distinct possibility due to valve 19 remain-
25
	 ing open for long periods during_ high power operations
26 which may be years in durat-on.
27
	 The present invention. is depicted in block form
28
	 in Figure 2.	 In the preferred embodiment, a TEMP/jet
29 pump combination 22/23 comprises a safety system which
30
	 is self-regulating and free of all moving parts. The
31
	 operation of this novel invention will now be described.
32
	
It should be appreciated that the reactor,
33
	 during operation, may reach _a temperature in the order
34
	
of 1200°K to 1500°K (roughly 1700°F to 2200°F). Typical
35
	
of well-known coolants for such a reactor is sodium or
0
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1 potassium or the like. The coolant metal is a very cor-
2 rosive material. In the interior of reactors, the metal
3 becomes elevated to the reactor's interior temperature.
4 outside of the reactor (based upon a given set of opera-
5 tions), the coolant temperature is in the order of 900°K
	
6
	 (1200"P).
	
7
	 The heat of the coolant is used to advantage
8 in this invention by providing a self-regulating and
9 self-powered safety system. The withdrawal point 25 for
10 the hot metal coolant 26 should be located at a point in
11 the system which is safely upsti.eam from a flow restric-
12 tion. The location of withdrawal and reinjection points,
13 as is well known to those of ordinary skill in the art,
14 shall guard against self-recirculation by the TEMP/jet
15 pump combination.
	
16
	 Assume that the primary coolant pump 12 stops
17 either intentionally or accidentally. The main flow of
18 the hot conductive metal has momentum and tends to
19 continue its flow. That momentum is used to advantage
20 in this invention.
	
21
	 The withdrawn hot metal 28 is a good electrical
22 conductor. The TEMP 22 generates a magnetic field using
23 electrical energy from thermoelectric elements driven by
24 the heat of the hot metal 28. The magnetic field, in a
25 well-known manner, moves the electrically conductive
26 metal 28. The field is proportional to the heat and
27 thus will diminish as the coolant. ' cools down. Accord-
28 ingly, the coolant 26;28 continues to circulate in the
29 same direction that the coolant was circulating when the
30 reactor (not shown) shut down. The withdrawn coolant is
31 raised to a high pressure at the output side of TEMP 22.
32 That high pressure is fed into the drive side 23A of the
	
33
	 jet pump 23 where the pressure is converted to velocity.
34 A jet pump 23, as well known in the art, reacts to the
35 high velocity to drag the main flow stream along with it. j
N bar 1;^
-6-
	
1
	 The main flow 26, 27 is larger, slower and at
2 a lower pressure than the withdrawn coolant 28 through
3 the TEMP 22. That main flow is through the main opening
4 of jet pump 23. The output side 27 from the jet pump 23
5 is circulated through the reactor's cooling system in a
6 standard manner.
	
7
	 Since the TEMP responds to the heat in the
8 coolant 26, the withdrawn coolant 28 circulates with
9 greater pressure and velocity when the coolant is
10 hottest. As the coolant continues to circulate, the
11 coolant loses its temperature and the coolant's velocity
12 is slower. At a safe lower temperature, the coolant
'3 circulation stops. By the time the circulation stops,
14 the reactor's time decay heat is no longer a problem.
	
15
	 As soon as the coolant warms up again on the
16 next reactor operation, the TEMP 22 and jet pump 23 auto-
	
17
	
matically resume functioning. 	 Although the TEMP/jet
18 pump combination operates while the reactor is on, the
19 flow is small compared to the main flow. Thus, the
	
20
	 system's efficiency is not diminished. Obviously, the
21 safety factor is greatly enhanced by this invention,
22 which provides a circulation system without any moving
23 parts and which is self-regulating.
24 If a small amount of stand-by energy is avail-
25. able, the TEMP could be replaced by an electrically-
26' driven centrifugal pump of any, well-known type. Such a
27 pump, however, does have moving 'parts and thus is not
28 the most preferred embodiment.
	
29
	 Other modifications will readily suggest them-
30 selves to those of ordinary skill in the art without
	
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	 departing from the spirit and scope of the claimed
	
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	 invention.
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JET PUMP-DRIVE SYSTEM FOR HEAT REMOVAL
ABSTRACT OF THE DISCLOSURE
The inventiorx does away with the necessity of
moving parts such as a check valve in a nuclear reactor
cooling system. Instead, a jet pump, in combination
with a TEMP, is employed to assure safe cooling of a
nuclear reactor after shutdown. A main flow exists for
a reactor coolant. A point ol, withdrawal is provided
for a secondary flow. A TEMP, responsive to the heat
from said coolant in the secondary flow path, automati-
cally pumps said withdrawn coolant to a higher pressure
and thus higher velocity compared to the main flow. The
high velocity coolant is applied as a driver flow for
the jet pump which has a main flow chamber located in
the main flow circulation pump. Upon nuclear shutdown
and loss of power for the main reactor pumpinj system,
the TEMP/jet pump combination continues to boost the
coolant flow in the direction it is already circulating.
During the decay time for the nuclear reactor, the jet
pump 'reeps running until the coolant temperature drops
to a lower and safe temperature where the heat is no
longer a problem. At this lower temperature, the TEMP/
jet pump combination ceases its circulation boosting
operation. When the nuclear_ reactor is restarted and
the coolant again exceeds the lower temperature setting,
the TEMP/jet pump automatically resumes operation. The
TEMP/jet pump , combination is thus automatic, self-
regulating and provides an emergency pumping system free
of moving parts.
5


Jet pump-drive system for heat removal

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