Swanson TRIGA Pulse

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Department of Nuclear Engineering And Radiation Health Physics TRIGA PULSING EXPERIMENT Report from a laboratory experiment conducted on 19 April 2012 as part of NE 116 Scott Swanson 931-637-511
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Transcript of Swanson TRIGA Pulse

Department of Nuclear Engineering And Radiation Health Physics

TRIGA PULSING EXPERIMENTReport from a laboratory experiment conducted on 19 April 2012 as part of NE 116

Scott Swanson 931-637-511

TRIGA PULSING EXPERIMENT Scott Swanson

May 3, 2012 NE 116

Abstract:The objective of this lab is to observe the pulsing operation of the OSTR and examine the results. Once observed, the results are broken down and analyzed by initial reactor power level, pulse reactivity, peak fuel temperature from the digital console readout, peak fuel temperature from the log channel on reactor console, peak reactor power from the linear channel on reactor console and energy reading on the console power range monitor. This report will look at all 8 pulses, but focus on the two pulses that occurred on April 19th, 2012.

College of Engineering and Science

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TRIGA PULSING EXPERIMENT Scott Swanson

May 3, 2012 NE 116

Table of Contents Abstract: ........................................................................................................................................... i 1. Introduction and Background .................................................................................................. 1 2. Theory ...................................................................................................................................... 1 3. Procedure ................................................................................................................................. 2 4. Data .......................................................................................................................................... 3 5. Analysis of Data (Lab Report Questions) ................................................................................ 5 6. References ................................................................................................................................ 9

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TRIGA PULSING EXPERIMENT Scott Swanson

May 3, 2012 NE 116

1.

Introduction and BackgroundThe TRIGA reactor is designed and instrumented to undergo significant power pulses. The reactor is first brought to criticality at a low power level with the transient rod in the core. The transient rod is designed to be pneumatically withdrawn in a very short period of time. Upon rod removal, the reactor power increases to a value that produces a fuel temperature, which compensates for the excess reactivity inserted. This is the peak power and is reached in a matter of a few milliseconds. Fuel temperature continues to rise with an increasing loss of reactivity and the reactor power decreases to a comparatively low steady state value. The final steady state power depends on the reactivity insertion and the heat transfer characteristics of the fuel. The steady state power level after the transient is referred to as the after pulse "tail." (Lab Worksheet)

2.

TheoryFor a reactor, which is critical on prompt neutrons alone, i.e. the reactivity insertion is greater than $1.00; the power will take on a rapidly rising exponential shape with time. If all feedback mechanisms are ignored the power rise as a function of time, P(t), will follow P(t) = P0 et/T (1) Where P0 is the initial reactor power at time t = 0, P(0), and T, the reactor period, is given by T = l / (k-1) (2) Where l is the prompt neutron lifetime in the reactor. This model, however, can only be used to examine the fast rising initial part of the TRIGA pulse because it does not include any temperature feedback effects in the reactor. (Lab Worksheet) The Fuchs-Nordheim model better describes the time behavior of a reactor with a large prompt negative temperature coefficient when there is a sudden insertion of a large amount of reactivity. This model makes two primary assumptions during the pulse: (1) delayed neutrons can be neglected, and (2) all heat generated remains in the fuel. The model relates such important parameters as flux or power, reactivity, temperature change, and energy released. Let = Delayed neutron fraction = Reactivity = (k-1)/k $ = Reactivity in dollar units = / l = Prompt neutron lifetime = Negative temperature coefficient T(t) = Fuel temperature change Cp = Specific heat of the reactor E(t) = Total energy released in the pulse up to time t P(t) = Reactor power as a function of time

College of Engineering and Science

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TRIGA PULSING EXPERIMENT Scott Swanson

May 3, 2012 NE 116

Skipping all of the details and if Cp and are assumed to be constant, then Peak Power( )

( )

Maximum Temperature Change ( ) ( )

Pulse Width (FWHM = Full Width at Half Maximum) ( Total Energy Release ( ) Also ( ) and ( ) ( ) [ ( ) ( )] ( )( ( ) ( )) ( ) ( ) )

At high powers, better results are obtained if Cp and are assumed to be linearly dependent on temperature. Values of LEU fuel parameters used at the OSTR are: | | [ ] ( )[ ] [ ]

Note that as of 5/20/09, there are 87 fuel elements and 3 fuel followed control rods (FFCRs) in the OSTR core. The FFCRs are withdrawn approximately 2/3 of the way out of the core during a pulse. (Lab Worksheet)

3.

Procedure

Configure the Control Room PC-DAS to record the reactor power and temperature every 0.5 ms (2000 samples/sec) for 30 seconds. Peak power during a pulse is displayed on a dedicated meter on the reactor console (units of percent of 1000 MW for pulse-low and 4000 MW for pulseCollege of Engineering and Science

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TRIGA PULSING EXPERIMENT Scott Swanson

May 3, 2012 NE 116

high). Fuel temperature can be read on the digital console readout. The integrated power, or energy, can be determined by integrating the power curve obtained with the PC data recording software, or from the energy reading on the power range monitor (units of percent of 20 Mw-s for pulse low and 80 Mw-s for pulse high). The pulse width can be measured directly from the PC power data. Several pulses will be obtained for different reactivity insertions. Operating procedures to pulse the TRIGA reactor: 1. Leave the transient rod disconnected from the carriage (no air). 2. Take the reactor critical at 15 W with the other three control rods evenly banked. 3. From the transient rod calibration curve, withdraw the transient rod carriage (still no air) to the proper setting for the size of pulse desired. 4. While in steady state, turn the range switch to 1 MW (pulse). 5. Turn the mode selector to pulse low ($1.75) or pulse high (>$1.75). 6. Fire the transient rod by pushing the READY button as soon as possible after starting data acquisition with the PC. Remember to note the highest value of fuel temperature on the digital meter. For comparison purposes, also record peak power and integrated power from the console instruments. Temperature will peak several seconds after the pulse, so the pulse should be initiated as soon as possible after data collection is started.

4.

Data

*Pulses 1 and 2 were ones that I witnessed. Table 1. Reactor Output DataSymbol $ l Cp E(t) P(t) Description Delayed neutron fraction Reactivity = (k-1)/k Reactivity in dollar units = / Prompt neutron lifetime Negative temperature coefficient Specific heat of the reactor Total energy released in the pulse up to time t Reactor power as a function of time Pulse 1* 0.0075 1.0095 $1.25 23[s] (2.3x10^-6) 42.213 Constant 1.55 Pulse 2* 0.0075 1.0095 $1.97 23[s] (2.3x10^-6) 10.642 Constant 5.04

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TRIGA PULSING EXPERIMENT Scott Swanson

May 3, 2012 NE 116

Table 2. Data Collection TableActivityRecord INITIAL REACTOR POWER LEVEL Record PULSE REACTIVITY Record PEAK FUEL TEMPERATURE from the digital console readout

Pulse 1*0.005 V

Pulse 2*0.002 V

Pulse 30.002 V

Pulse 40.002 V

Pulse 50.005 V

Pulse 60V

Pulse 70.002 V

Pulse 80.005 V

$1.25 123C

$1.97 399C

$1.75 255C

$1.50 194C

$1.75 225C

$1.50 190C

$1.35 152C

$1.90 289C

Record PEAK 0.630 V 0.601V 0.525 V FUEL TEMPERATURE from the log channel on reactor console Record PEAK 99 MW 1512 952 MW REACTOR MW POWER from the linear channel on reactor console Record ENERGY 1.55 kW- 5.04 kW- 3.8 kWREADING on the Hr Hr Hr console power range monitor *Note: Pulse 1 and 2 will be the pulses witnessed.

0.560 V

0.532 V

0.532 V

0.532 V

0.527 V

404 MW

952 MW

376 MW

200 MW

1420 MW

2.2 kWHr

4.24 kWHr

2.78 kWHr

2.15 kWHr

5.111 kWHr

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TRIGA PULSING EXPERIMENT Scott Swanson

May 3, 2012 NE 116

5.I.

Analysis of Data (Lab Report Questions)

Question #1 - From the experimental data for each pulse, plot the power asa function of time. Also plot the results from equation (1) for each pulse for comparison: (This answer is reflected only towards the two pulses I witnessed). Pulse 1 Pulse 2

Power rise as a function of P(t): ( )

Power rise as a function of P(t): ( )

The following graph shows the power rise as a function from P(t) = 0 to P(t) = 50 milliseconds (.05).

You can observe from the graphs that pulse 1 appears to be growing faster until a certain point at which pulse 2 surpasses it and grows at an inreasing exponential rate over pulse 1.

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TRIGA PULSING EXPERIMENT Scott Swanson

May 3, 2012 NE 116

II.

Question #2 - For each pulse plotted compare the peak power, maximumtemperature change, pulse width (FWHM), and total energy release:

Figure 1.1600 1400 1200 1000 800 600 400 200 0 Reactivty Peak Temp Peak Power Energy Pulse 1 Pulse 2 Pulse 3 Pulse 4 Pulse 5 Pulse 6 Pulse 7 Pulse 8

Table 3. Reactivity Peak Temp Peak Power Energy Pulse 1 1.25 123 99 1.55 Pulse 2 1.97 399 1512 5.04 Pulse 3 1.75 253 956 3.8 Pulse 4 1.5 194 404 2.2 Pulse 5 1.75 255 952 4.24 Pulse 6 1.5 190 376 2.78 Pulse 7 1.35 152 200 2.15 Pulse 8 1.9 289 1420 5.11

III.

Question #3 - What differences and similarities do you see between theresults and the various model predictions for each pulse analyzed? Compare peak power, maximum temperature change, pulse width, and total energy release: (This answer is reflected only towards the two pulses I witnessed) This is my first nuclear engineering lab Ive done. Ive also not taken physics or chemistry, and some of the math used in this lab I have not yet learned (Currently in MTH 251 so the integral formula had me a bit lost). My origional theory on how the two pulses would compare with eachother turned to be the opposite of my theory. I assumed a) Peak Power: For peak power my prediction was correct just because I assumed that the high pulse would generate a substanially larger amount of power than the low pulse.

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TRIGA PULSING EXPERIMENT Scott Swanson

May 3, 2012 NE 116

b) Maximum Temptarure Change: I wasnt able to determine the initial temptature of the reactor. c) Pulse Width (FWHM): Low Pulse FWHM = .00423 High Pulse FWHM = .00109

I assumed that the high pulse would have a larger FWHM than the low pulse. After looking at the data and seeing that, that wasnt the case. My next theory as to why this is the case is because the high pulse is moving at 1,527% the speed of the low pulse therefore the high pulse is stretched out thinner than a slower moving low pulse. d) Total Energy Release: The high pulse pushed out 3.49KW-hr more than the low pulse. I expected the total energy release to be higher in the high pulse than the low pulse. My assumption is that the pulse reactivity and peak reactor power had the most direct affect on the total energy release. Whether the fuel temptature in the reactor affected the total energy release Im unsure of. I attempted research online but could not find any direct references to fuel temptature and total energy release.

IV.

Question #4 - What might be some of the reasons for the differences thatyou observed between the predictions and the results obtained? After looking at the data between all eight pulses its hard for me to determine without a more knowledgable understanding of how each of the variables (initial reactor power level, pulse reactivity, peak fuel temperature, peak reactor power, and energy reading) interact without eachother. Currently only having a basic understanding of a TRIGA pulse experiment and the different concepts of understanding how a reactor works I was still able to derive a few key differences and predictions about the results obtained. If you look back at figure 1 under question #2 you can observe that pulses 2, 5, and 8 had a significantly higher peak power than pulses 1, 3, 4, 6, and 7 which were semi-closely grouped together under 400MW of peak power.

College of Engineering and Science

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TRIGA PULSING EXPERIMENT Scott Swanson

May 3, 2012 NE 116

Key observable differences: Pulses 2, 5, and 8: I. Reactivity 1.55

One unique discovery I made while analyzing the data (Figure 2.) was that pulse 3 had a higher peak power than pulse 5 (956>952) but a lower energy output than pulse 5 (3.8