As part of the Nuclear Systems Office Fission Surface Power Technology Demonstration Unit (TDU) project, a reactor simulator test loop (RxSim) was design & built to perform integrated testing of the TDU components. In particular, the objectives of RxSim testing was to verify the operation of the core simulator, the instrumentation and control system, and the ground support gas and vacuum test equipment. In addition, it was decided to include a thermal test of a cold trap purification design and a pump performance test at pump voltages up to 150 V since the targeted mass flow rate of 1.75 kg/s was not obtained in the RxSim at the originally constrained voltage of 120 V. This paper summarizes RxSim testing. The gas and vacuum ground support test equipment performed effectively in NaK fill, loop pressurization, and NaK drain operations. The instrumentation and control system effectively controlled loop temperature and flow rates or pump voltage to targeted settings. The cold trap design was able to obtain the targeted cold temperature of 480 K. An outlet temperature of 636 K was obtained which was lower than the predicted 750 K but 156 K higher than the cold temperature indicating the design provided some heat regeneration. The annular linear induction pump (ALIP) tested was able to produce a maximum flow rate of 1.53 kg/s at 800 K when operated at 150 V and 53 Hz. Keywords: fission, space power, nuclear, liquid metal, NaK

Pearson, Boise Jon

Schoenfeld, Michael P.

Webster, Kenny L.

As part of the Nuclear Systems Office Fission Surface Power Technology Demonstration Unit (TDU) project, a reactor simulator test loop (RxSim) was design & built to perform integrated testing of the TDU components. In particular, the objectives of RxSim testing was to verify the operation of the core simulator, the instrumentation and control system, and the ground support gas and vacuum test equipment. In addition, it was decided to include a thermal test of a cold trap purification design and a pump performance test at pump voltages up to 150 V since the targeted mass flow rate of 1.75 kg/s was not obtained in the RxSim at the originally constrained voltage of 120 V. This paper summarizes RxSim testing. The gas and vacuum ground support test equipment performed effectively in NaK fill, loop pressurization, and NaK drain operations. The instrumentation and control system effectively controlled loop temperature and flow rates or pump voltage to targeted settings. The cold trap design was able to obtain the targeted cold temperature of 480 K. An outlet temperature of 636 K was obtained which was lower than the predicted 750 K but 156 K higher than the cold temperature indicating the design provided some heat regeneration. The annular linear induction pump (ALIP) tested was able to produce a maximum flow rate of 1.53 kg/s at 800 K when operated at 150 V and 53 Hz

Pearson, Boise J.

NASA Technical Reports Server

DISTRIBUTION STATEMENT A.  Approved for public release; distribution is unlimited. 
 
This work was done in support of the Fission Power Systems Technology Demonstration Unit funded by the Office of the Chief 
Technologist.   
 
REACTOR SIMULATOR TESTING 
M.P. Schoenfeld, K.L. Webster and B.J. Pearson 
NASA MSFC/Propulsion Systems & Technology Branch/Nuclear Systems Team 
Huntsville, AL 
ABSTRACT 
As part of the Nuclear Systems Office Fission Surface Power Technology Demonstration Unit 
(TDU) project, a reactor simulator test loop (RxSim) was design & built to perform integrated testing of the 
TDU components.  In particular, the objectives of RxSim testing was to verify the operation of the core 
simulator, the instrumentation and control system, and the ground support gas and vacuum test 
equipment.  In addition, it was decided to include a thermal test of a cold trap purification design and a 
pump performance test at pump voltages up to 150 V since the targeted mass flow rate of 1.75 kg/s was 
not obtained in the RxSim at the originally constrained voltage of 120 V.  This paper summarizes RxSim 
testing.  The gas and vacuum ground support test equipment performed effectively in NaK fill, loop 
pressurization, and NaK drain operations.  The instrumentation and control system effectively controlled 
loop temperature and flow rates or pump voltage to targeted settings.  The cold trap design was able to 
obtain the targeted cold temperature of 480 K.  An outlet temperature of 636 K was obtained which was 
lower than the predicted 750 K but 156 K higher than the cold temperature indicating the design provided 
some heat regeneration.  The annular linear induction pump (ALIP) tested was able to produce a 
maximum flow rate of 1.53 kg/s at 800 K when operated at 150 V and 53 Hz.    
INTRODUCTION 
A 40 kWe fission power system Technology Demonstration Unit (TDU) is being developed under 
the Fission Power Systems project.  The TDU is comprised of a non-nuclear core simulator, sterling 
engine power conversion system, Annular Linear Induction Pump (ALIP), liquid sodium/potassium (NaK) 
coolant, and radiator heat rejection.  In support of TDU development, the RxSim test loop was developed 
to perform integrated component testing to verify operability prior to the TDU development.  The RxSim 
was a NaK filled test loop comprising of a 37 pin reactor core simulator, NaK-GN2 HX (for simulating the 
thermal load of the sterling power conversion system), an electromagnetic flow meter, and the TDU ALIP.  
In addition, although not part of the TDU, the RxSim had a secondary bypass loop across the ALIP to test 
a cold trap purification design.  Figure 1 shows the RxSim layout.  This report covers testing in the RxSim 
loop while details of the design and development are in a separate report. 
 
https://ntrs.nasa.gov/search.jsp?R=20130014191 2019-08-29T16:16:52+00:00Z
FIGURE 1. RxSim Test Loop Layout. 
REACTOR SIMULATOR OPERATION AND CONTROL 
Reactor simulator control systems were develop to provide the following five modes of operation 
for operations: basic, power, power ramp, temperature and reactor simulator function (RSF). Figure 2 
shows the user interface panel for operating the RxSim. 
 
 
 
FIGURE 2. User Interface Panel for the RxSim Control. 
 
The basic control mode allows the operator to control the individual voltage and current settings 
for each of the 12 heater zones of the core simulator. Figure 3 shows the user interface panel for this 
control mode. This panel also provides a mechanism for calibrating the analog command used to control 
the current setting of each power supply. 
 
 
FIGURE 3. User Interface Panel for Basic Control Mode. 
 
Each of the 12 zones can operate in constant current or constant voltage mode depending on the 
voltage and current settings. When the load attempts to draw more current than the current setting, 
constant current mode is enabled. Otherwise, constant voltage mode is enabled. The voltage and current 
settings for each zone are limited to 150 V and 100 A, respectively. 
 
The power control mode allows the operator to control the total power setting for the core. The 
power delivered to the core is distributed to each of the 12 heater zones according to weighting factors 
specified by the operator. For all operations to date, all weighting factors have been set to 1.0 so that the 
power is distributed evenly among all 12 heater zones. The power to a zone is controlled by operating its 
power supply in constant current mode. Current and voltage measurements for each zone are used to 
calculate the load resistance and the target set points required to achieve the desired power setting. As 
new measurements are taken, the current setting is adjusted to compensate for changes in the load 
resistance. When starting from a power setting of zero, the current and voltage settings of a zone are 
gradually increased until useable current and voltage measurements are obtained. The total power 
setting and power rate of change are limited and constrained by the maximum power and slew rate 
setting specified by the operator. The following power control configuration dialog is provided for the 
operator to specify the maximum power, maximum slew rate and weighting factors. 
 
 
 
FIGURE 4. User Interface For Configuration Settings of the Core Power Control Mode 
 
The power ramp control mode allows the operator to ramp the total power from a starting set 
point to a new set point over a specified period of time. Once the desired power is achieved, the control 
mode switches to the power control mode to maintain the new power setting. The ramp rate is limited by 
the maximum slew rate specified in the power control configuration dialog. 
 
The temperature control mode allows the operator to control the NaK outlet temperature of the 
core. This mode uses 2 control loops to achieve temperature control. When the difference between the 
outlet temperature measurement and the set-point is less than a specified limit, a temperature control 
loop is used. Otherwise, a temperature rise rate control loop is used. This insures that the temperature 
does not rise or fall too rapidly when the difference between the measurement and set-point are large.  
Each of the control loops combines a feedback (closed-loop) PID controller with a feed-forward (open-
loop) control. Feed-forward control uses knowledge about the system to estimate the power setting 
required to achieve the desired set-point, while the PID controller responds to differences between the 
set-point and the actual measured temperature and adjusts the power setting to eliminate those 
differences. Although the open-loop estimate is not perfect, it does provide most of the power setting 
required to achieve the set-point. The combination of feed-forward and PID control greatly improves 
overall system performance compared with PID control alone. The open-loop power setting estimates for 
temperature control are given by equation 1 and temperature rise rate given by equation 2. 
 
    44 ctipitpt TTATcTcm    [1] 
    44 ooipiopoopcc TTATcTcmTcm    [2] 
 
In order to insure bump less transfer when the temperature control mode is activated and when 
switching between temperature and temperature rise rate control loops, both loops continue to perform 
control calculations even when inactive. Figure 5 shows the user interface for tuning these control loops. 
 
 
 
FIGURE 5. User Interface For Tuning Temperature And Temperature Rise Rate Control Loops 
The RSF mode enables remote control of the core power by a LabVIEW application running on a 
National Instruments cRIO-9024 real-time controller. The application runs a Simulink model which 
simulates the response of a real nuclear reactor. Two TCP network connections are used to communicate 
with the application. Feedback in the form of the core inlet temperature, NaK pressure and NaK mass 
flow rate is provided to the application over one connection. The core power setting and various model 
outputs are returned over the other connection. The RSF mode can only be enabled when both TCP 
connections are active with no errors and when the core outlet temperature is within an operator specified 
range. If either connection is lost or the outlet temperature goes out of range, the control mode switches 
to temperature control mode to take the system back to the operator specified temperature set-point. 
Figure 6 shows the user interface for specifying the temperature limits and configuring the TCP 
communication. 
 
 
 
FIGURE 6. User Interface For Specifying Temperature Limits and TCP Communication Regarding the 
Reactor Simulator Function Control Mode. 
CONTROL FOR ALIP OPERATION 
Two modes of operation are provided for operating the ALIP: voltage and flow rate. Figure 7 
shows the user interface for operating the ALIP. 
 
 
FIGURE 6. User Interface For ALIP Operation. 
 
The voltage control mode allows the operator to control the line-to-line voltage setting of the ALIP 
power supply. To insure that there are no abrupt changes in voltage while the pump is operating, new 
settings are limited by an operator specified slew rate. The voltage setting is limited to 150 VAC. 
 
The flow rate control mode allows the operator to control the NaK mass flow rate. This mode is 
implemented with a control loop that combines a feedback (closed-loop) PID controller with feed-forward 
(open-loop) control. Feed-forward control uses knowledge about the system to estimate the voltage 
setting required to achieve the desired set-point, while the PID controller responds to differences between 
the set-point and the actual measured flow rate and adjusts the voltage setting to eliminate those 
differences. A linear curve fit of the measured flow rate at various voltage settings was used for the open-
loop estimate. The differences due to nonlinearity and changes in temperature dependent fluid 
characteristics were easily compensated for by the PID controller. The combination of feed-forward and 
PID control greatly improves overall system performance compared with PID control alone. In order to 
insure bump less transfer when flow rate control is activated, the control loop continues to perform control 
calculations even when inactive. Figure 7 shows the user interface for tuning these control loops. 
 
 
 
FIGURE 7. User Interface For Tuning ALIP Operation Control Loop. 
 
 
RESULTS AND DISCUSSION 
RxSim testing involved operational checkouts of the loop control and instrumentation system and 
the gas and vacuum test support equipment.  To accomplish this, the RxSim was to be operated at TDU 
representative temperatures and flow rates (800 K and 1.75 kg/s).  Vacuum and gas support equipment 
were used for NaK transfer operations (evacuating the RxSim loop, lower reservoir or accumulator, 
applying Ar pressure head, and actuating a remote operating valve).  The gas system also supported the 
TDU ALIP by supplying and regulating (relief valve and regulator in conjunction) He pressure in the 
electrical areas of the ALIP.  In the past, this support equipment was provided by the test facility.   These 
gas and vacuum racks were built to provide dedicated support equipment for the TDU.  The vacuum and 
gas support equipment proved to be sufficient.  The system’s control and instrumentation program 
provided control algorithms to operate the loop at targeted core outlet temperatures and either mass flow 
rates or pump voltage.  The control algorithms also controlled the slew rate within constraints.  These 
algorithms proved to be sufficient and effective.  
During the first series of test, pump voltages and frequencies were ramped up and varied to 
achieve the maximum flow rate.  It was found that the maximum flow rate obtainable in the RxSim loop 
with the TDU ALIP pump was about 1.33 kg/s (when the ALIP was provided 120 V at 55 Hz and a NaK 
temperature of 800 K).  Thus it was decided to extend the pump to a maximum of 150 V in which a 
maximum flow rate of 1.53 kg/s was obtained (Figure 2). 
 
Figure 2. Expanded Pump Testing up to 150 V at Tcoreout = 800 K.  Maximum Mass Flow Rate Observed 
for the TDU ALIP in the RxSim Test Loop was 1.5 kg/s at 150 V and 73 Hz. 
 
Thermal performance of a cold trap design with heat regeneration was tested.  The design 
consisted of a bellows jacketed GN2-NaK HX for cooling and accommodating thermal expansion.  The 
NaK flow path consisted of a downcomer flow through alternating disk and donut baffles to create cross 
flow and increase NaK residing time within the cold trap.  The volume between the baffles was packed 
with stainless steel wool to provide a reaction surface for oxide precipitation.  The return flow path was 
through a tube running up the centerline of the cold trap and then terminating in a coil that was bathed in 
hot NaK from the inlet at the top of the cold trap. A cold temperature of 480 K was the targeted goal of the 
cold trap design as analysis had indicated that purification of the NaK could be obtained within a 
reasonable period of time with this cold temperature.  The analysis also indicated that a return flow 
through a coil would provide sufficient heat regeneration so cold NaK would not be put back into the 
system acting a thermal load.  However, for this performance, the analysis indicated that a very slow NaK 
flow rate was required.  The design proved to provide a good cooling capacity to reach a sufficiently low 
cold temperature with slow NaK flow rates as predicted.  Heat regeneration was observed to occur more 
effectively within the cold trap return line than predicted but not as effectively within the coil regenerator 
than predicted.  An outlet temperature of about 750 K was predicted but 636 K was observed (Figure 3). 
 
Figure 3. Cold Trap Design and Performance.  Left:  Cold Trap Design.  Dots Correspond to the 
Locations of the Thermocouple Probe Locations. Right:  Comparison of Cold Trap Thermal Model and 
Measured Temperatures.  The Modeled Flow Rates were 0.00635 kg/s (NaK) and 0.078 kg/s (N2).  The 
Actual NaK Flow Rate Through the Cold Trap was not Measured but in the Primary Loop it was 0.068 
kg/s with the Cold Trap Loop Bypass Valve Open ¼ turn.  The Actual N2 Flow Rates Were Not Measured 
but the Supply Pressure was 6 psi Above Ambient.  Modeled Inlet Temperature was Set to Actual Cold 
Trap Inlet Temperature of 800 K.  NaK & GN2 Mass Flow Rates were Then Tweaked to Get Modeled Tcold 
Approximately Equal to Measured Tcold.  Yellow Dots are Model Temperature Predictions at Locations 
Expected to Correspond with Thermocouple Probe Locations Which are the Green Triangles.   
 
SUMMARY AND CONCLUSIONS 
Integrated testing of the TDU control and instrumentation, vacuum and gas ground test support 
equipment, and reactor core simulator components in the RxSim test loop demonstrated them to be 
operationally ready for TDU integration.  The ALIP pump was found to not produce the desired flow rate 
for the RxSim test loop and thus is being considered as a backup pump for TDU testing.  In addition, heat 
regeneration design feature for cold trap purification was demonstrated with thermal testing of a cold trap 
integrated into the RxSim test loop. 
ACKNOWLEDGMENTS 
This work was done in support of the Fission Power Systems Technology Demonstration Unit 
funded by the Office of the Chief Technologist. 


Reactor Simulator Testing

Pearson, Boise J..

Abstract Submittal Form JANNAF
60th JPM /  9th MSS / 7th LPS / 6th SPS
Joint Subcommittee Meeting
29 April – 3 May 2013
Abstract Due Date: Monday, October 22, 2012
Unclassified Abstract (250 – 300 words; do not include figures or tables) 
As part of the Nuclear Systems Office Fission Surface Power Technology Demonstration Unit (TDU) project, a reactor simulator test loop (RxSim) 
was design & built to perform integrated testing of the TDU components.  In particular, the objectives of RxSim testing was to verify the operation 
of the core simulator, the instrumentation and control system, and the ground support gas and vacuum test equipment.  In addition, it was 
decided to include a thermal test of a cold trap purification design and a pump performance test at pump voltages up to 150 V since the targeted 
mass flow rate of 1.75 kg/s was not obtained in the RxSim at the originally constrained voltage of 120 V.  This paper summarizes RxSim testing.  
The gas and vacuum ground support test equipment performed effectively in NaK fill, loop pressurization, and NaK drain operations.  The 
instrumentation and control system effectively controlled loop temperature and flow rates or pump voltage to targeted settings.  The cold trap 
design was able to obtain the targeted cold temperature of 480 K.  An outlet temperature of 636 K was obtained which was lower than the 
predicted 750 K but 156 K higher than the cold temperature indicating the design provided some heat regeneration.  The annular linear induction 
pump (ALIP) tested was able to produce a maximum flow rate of 1.53 kg/s at 800 K when operated at 150 V and 53 Hz.    
 By submitting an abstract, you agree to both complete a final paper for publication and to attend the meeting to present this information.  
 Submit abstracts electronically; submittal instructions are found in the call for papers.  
 Direct questions to Patricia Szybist, by phone at 410.992.7302 x 215, or email to pats@jhu.edu.
https://ntrs.nasa.gov/search.jsp?R=20130014159 2019-08-29T16:16:04+00:00Z


Proceedings of Nuclear and Emerging Technologies for Space 2013 
Albuquerque, NM, February 25-28, 2013 
Paper 6822 
Reactor Simulator Testing 
 
Michael P. Schoenfeld1, Kenny L. Webster1, Boise J Pearson3  
1NASA Marshall Space Flight Center ER24 Huntsville, AL  35812 
(256) 961-0078, j.boise.pearson@nasa.gov 
Abstract. As part of the Nuclear Systems Office Fission Surface Power Technology Demonstration Unit (TDU) 
project, a reactor simulator test loop (RxSim) was design & built to perform integrated testing of the TDU 
components.  In particular, the objectives of RxSim testing was to verify the operation of the core simulator, the 
instrumentation and control system, and the ground support gas and vacuum test equipment.  In addition, it was 
decided to include a thermal test of a cold trap purification design and a pump performance test at pump voltages up 
to 150 V since the targeted mass flow rate of 1.75 kg/s was not obtained in the RxSim at the originally constrained 
voltage of 120 V.  This paper summarizes RxSim testing.  The gas and vacuum ground support test equipment 
performed effectively in NaK fill, loop pressurization, and NaK drain operations.  The instrumentation and control 
system effectively controlled loop temperature and flow rates or pump voltage to targeted settings.  The cold trap 
design was able to obtain the targeted cold temperature of 480 K.  An outlet temperature of 636 K was obtained 
which was lower than the predicted 750 K but 156 K higher than the cold temperature indicating the design provided 
some heat regeneration.  The annular linear induction pump (ALIP) tested was able to produce a maximum flow rate 
of 1.53 kg/s at 800 K when operated at 150 V and 53 Hz.    
Keywords: fission, space power, nuclear, liquid metal, NaK.  
BACKGROUND 
A 40 kWe fission power system Technology Demonstration Unit (TDU) is being developed under the Fission Power 
Systems project.  The TDU is comprised of a non-nuclear core simulator, sterling engine power conversion system, 
Annular Linear Induction Pump (ALIP), liquid sodium/potassium (NaK) coolant, and radiator heat rejection.  In 
support of TDU development, the RxSim test loop was developed to perform integrated component testing to verify 
operability prior to the TDU development.  The RxSim was a NaK filled test loop comprising of a 37 pin reactor 
core simulator, NaK-GN2 HX (for simulating the thermal load of the sterling power conversion system), an 
electromagnetic flow meter, and the TDU ALIP.  In addition, although not part of the TDU, the RxSim had a 
secondary bypass loop across the ALIP to test a cold trap purification design.  Figure 1 shows the RxSim layout.  
This report covers testing in the RxSim loop while details of the design and development are in a separate report. 
https://ntrs.nasa.gov/search.jsp?R=20130011195 2019-08-31T00:17:26+00:00Z
Proceedings of Nuclear and Emerging Technologies for Space 2013 
Albuquerque, NM, February 25-28, 2013 
Paper 6822 
 
FIGURE 1. RxSim Test Loop Layout. 
TESTING 
RxSim testing involved operational checkouts of the loop control and instrumentation system and the gas and 
vacuum test support equipment.  To accomplish this, the RxSim was to be operated at TDU representative 
temperatures and flow rates (800 K and 1.75 kg/s).  Vacuum and gas support equipment were used for NaK transfer 
operations (evacuating the RxSim loop, lower reservoir or accumulator, applying Ar pressure head, and actuating a 
remote operating valve).  The gas system also supported the TDU ALIP by supplying and regulating (relief valve 
and regulator in conjunction) He pressure in the electrical areas of the ALIP.  In the past, this support equipment was 
provided by the test facility.   These gas and vacuum racks were built to provide dedicated support equipment for the 
TDU.  The vacuum and gas support equipment proved to be sufficient.  The system’s control and instrumentation 
program provided control algorithms to operate the loop at targeted core outlet temperatures and either mass flow 
rates or pump voltage.  The control algorithms also controlled the slew rate within constraints.  These algorithms 
proved to be sufficient and effective.  
During the first series of test, pump voltages and frequencies were ramped up and varied to achieve the maximum 
flow rate.  It was found that the maximum flow rate obtainable in the RxSim loop with the TDU ALIP pump was 
about 1.33 kg/s (when the ALIP was provided 120 V at 55 Hz and a NaK temperature of 800 K).  Thus it was 
decided to extend the pump to a maximum of 150 V in which a maximum flow rate of 1.53 kg/s was obtained 
(Figure 2). 
 
FIGURE 2. Expanded Pump Testing up to 150 V at Tcoreout = 800 K.  Maximum Mass Flow Rate Observed for the TDU ALIP in 
the RxSim Test Loop was 1.5 kg/s at 150 V and 73 Hz. 
Proceedings of Nuclear and Emerging Technologies for Space 2013 
Albuquerque, NM, February 25-28, 2013 
Paper 6822 
Thermal performance of a cold trap design with heat regeneration was tested.  The design consisted of a bellows 
jacketed GN2-NaK HX for cooling and accommodating thermal expansion.  The NaK flow path consisted of a 
downcomer flow through alternating disk and donut baffles to create cross flow and increase NaK residing time 
within the cold trap.  The volume between the baffles was packed with stainless steel wool to provide a reaction 
surface for oxide precipitation.  The return flow path was through a tube running up the centerline of the cold trap 
and then terminating in a coil that was bathed in hot NaK from the inlet at the top of the cold trap. A cold 
temperature of 480 K was the targeted goal of the cold trap design as analysis had indicated that purification of the 
NaK could be obtained within a reasonable period of time with this cold temperature.  The analysis also indicated 
that a return flow through a coil would provide sufficient heat regeneration so cold NaK would not be put back into 
the system acting a thermal load.  However, for this performance, the analysis indicated that a very slow NaK flow 
rate was required.  The design proved to provide a good cooling capacity to reach a sufficiently low cold 
temperature with slow NaK flow rates as predicted.  Heat regeneration was observed to occur more effectively 
within the cold trap return line than predicted but not as effectively within the coil regenerator than predicted.  An 
outlet temperature of about 750 K was predicted but 636 K was observed (Figure 3). 
 
FIGURE 3. Cold Trap Design and Performance.  Left:  Cold Trap Design.  Dots Correspond to the Locations of the 
Thermocouple Probe Locations. Right:  Comparison of Cold Trap Thermal Model and Measured Temperatures.  The Modeled 
Flow Rates were 0.00635 kg/s (NaK) and 0.078 kg/s (N2).  The Actual NaK Flow Rate Through the Cold Trap was not Measured 
but in the Primary Loop it was 0.068 kg/s with the Cold Trap Loop Bypass Valve Open ¼ turn.  The Actual N2 Flow Rates Were 
Not Measured but the Supply Pressure was 6 psi Above Ambient.  Modeled Inlet Temperature was Set to Actual Cold Trap Inlet 
Temperature of 800 K.  NaK & GN2 Mass Flow Rates were Then Tweaked to Get Modeled Tcold Approximately Equal to 
Measured Tcold.  Yellow Dots are Model Temperature Predictions at Locations Expected to Correspond with Thermocouple Probe 
Locations Which are the Green Triangles.   
CONCLUSION 
Integrated testing of the TDU control and instrumentation, vacuum and gas ground test support equipment, and 
reactor core simulator components in the RxSim test loop demonstrated them to be operationally ready for TDU 
integration.  The ALIP pump was found to not produce the desired flow rate for the RxSim test loop and thus is 
being considered as a backup pump for TDU testing.  In addition, heat regeneration design feature for cold trap 
purification was demonstrated with thermal testing of a cold trap integrated into the RxSim test loop. 
Proceedings of Nuclear and Emerging Technologies for Space 2013 
Albuquerque, NM, February 25-28, 2013 
Paper 6822 
NOMENCLATURE 
ALIP  = annular linear induction pump 
GN2  = gaseous nitrogen 
He   = helium 
HX  = heat exchanger 
K   = Kelvin 
NaK  = eutectic alloy of sodium (Na) and potassium (K) liquid metals 
RxSim = Reactor Simulator Test Loop 
TDU  = Technology Demonstration Unit 
ACKNOWLEDGMENTS 
This work was done in support of the Fission Power Systems Technology Demonstration Unit funded by the Office 
of the Chief Technologist. 


Reactor Simulator Testing

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