LA-UR-13-24213Approved for public release; distribution is unlimited.
Title: Godiva IV Assembly and Startup
Author(s): Goda, Joetta M.
Intended for: Nuclear Criticality Safety Program (NCSP) FY2013 Technical ReviewProgram, 2013-05-30 (Washington, District Of Columbia, United States)For publication in unclasssified minutes of meeting. LA-CP 13-00642was presented at meeting.
Issued: 2013-06-10
Disclaimer:Los Alamos National Laboratory, an affirmative action/equal opportunity employer,is operated by the Los Alamos National Security, LLC for the National NuclearSecurity Administration of the U.S. Department of Energy under contract DE-AC52-06NA25396. By approving this article, the publisher recognizes that the U.S. Government retains nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or to allow others to do so, for U.S. Government purposes. Los Alamos National Laboratory requests that the publisher identify this article as work performed under the auspices of the U.S. Departmentof Energy. Los Alamos National Laboratory strongly supports academic freedom and a researcher's right to publish; as an institution, however, the Laboratory does not endorse the viewpoint of a publication or guarantee its technical correctness.
UNCLASSIFIED
Godiva IVGodiva IVReassembly and Startup
Joetta Goda
May 2013
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
Slide 1UNCLASSIFIED
UNCLASSIFIED
Godiva Assembly OverviewGodiva Assembly Overview
• Cylindrical uranium metal fast burst assemblyfast burst assembly
• 65 kg, 93% enriched• 7-inch diameter (17.8 cm),
6-inch tall (15 2 cm)6 inch tall (15.2 cm)
• Core without safety block or control rods
• Multiplication ~10• keff ~ 0.9
• Assembly/Disassembly activity rarely performed
• 20051989
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
UNCLASSIFIED Slide 2
• 1989
UNCLASSIFIED
Criticality SafetyCriticality Safety
Fire suppression system shall be disabled during assembly operations.operations.
Fire suppression efforts or agents of any type are NOT allowed.
Table positioned ≥ 3 feet from any concrete surface.
Demarcated 3-inch buffer boundary. Full core must be in the hydraulic
press or within the buffer boundarypress or within the buffer boundary.
Maximum of 2 personnel may be within 2 feet of the full core when the Saturn ring is off.
Assembly table height ≥ 41 inches
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UNCLASSIFIED Slide 3
UNCLASSIFIED
Install Control Rods Burst Rod and Safety BlockInstall Control Rods, Burst Rod, and Safety Block
Measured position of top of control elements relative to top of Godiva stand at both out and in positions.
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UNCLASSIFIED Slide 4
UNCLASSIFIED
Upper Fuel AssemblyUpper Fuel Assembly
Thicker shim ring constructed to gcompensate for fuel lost over time.
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UNCLASSIFIED Slide 5
UNCLASSIFIED
Upper Fuel Assembly (continued)Upper Fuel Assembly (continued)
Load bearing steel ring placed on top of fuelg g p p
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UNCLASSIFIED Slide 6
UNCLASSIFIED
St k th L CStack the Lower Core
1 2
3 4
Alignment ofAlignment of grooves absolutely essential
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UNCLASSIFIED Slide 7
UNCLASSIFIED
Place Upper Fuel on Lower FuelPlace Upper Fuel on Lower Fuel
Audible indication of
Upper assembly lifted by crane and lowered Audible indication of
increased multiplication as upper assembly is lowered onto stack
and lowered onto lower stack.
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UNCLASSIFIED Slide 8
lowered onto stack.
UNCLASSIFIED
Install the C-ClampsInstall the C Clamps
First clamp is easiest.First clamp is easiest. Iterate to get all clamps seated satisfactorily.
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UNCLASSIFIED Slide 9
UNCLASSIFIED
Install the Support LegsInstall the Support Legs
Core is suspended while legs p gare attached.
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UNCLASSIFIED Slide 10
UNCLASSIFIED
Install the Saturn RingInstall the Saturn Ring
Bolts are tensioned outward. Measuring and adjusting for g j gequal distance to ensure even tension.
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
UNCLASSIFIED Slide 11
UNCLASSIFIED
Install the CoreInstall the Core
Table is rolled next to stand.Core lowered carefully over protrudingCore lowered carefully over protruding control rods.Brackets are bolted on.
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
UNCLASSIFIED Slide 12
UNCLASSIFIED
Install the Core (continued)Install the Core (continued)
Insert source in glory hole.Take subcritical neutronTake subcritical neutron multiplication measurements.
Results consistent with disassembly, multiplication ~8.
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UNCLASSIFIED Slide 13
UNCLASSIFIED
Set the Safety Block Gap
shims
Adjustment Set the Safety Block Gap
Use combinations of shims placed on top of Safety Block to measure gap distance
spacer
Safety Block to measure gap distanceAdjust Safety Block Position with spacerRepeat to measure gap distance.
Gap distance is between the thickness of shims where Safety Block will drop out and next smaller amount of shims where Safety
Final gap distance is 0 0145” 0 0175”
yBlock will not drop out.
Final gap distance is 0.0145 - 0.0175
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UNCLASSIFIED Slide 14Slide 14
UNCLASSIFIED
Approach to CriticalApproach to Critical
1/M on Safety Block position
1/M on Sum of Control Rod positions
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
UNCLASSIFIED Slide 15
UNCLASSIFIED
First Critical at DAFFirst Critical at DAF
Excess reactivity $1.07 compared to $1.23 prior to disassembly
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
UNCLASSIFIED Slide 16
UNCLASSIFIED
Reproducibility of Control ElementsReproducibility of Control Elements
Control Rod Safety Block Burst Rod
Insert CR 1
Find DC with CR 2
Establish positive period
Measure period
Insert BR
Establish positive period
Control Rod Safety Block Burst Rod
Record CR 2 position
Remove CR 2
p
Remove SB
Insert SB
p p
Measure period
Remove BR
Repeat Repeat Repeat0.250 ± 0.001 in 45.07 ± 0.59 sec 21.34 ± 0.41 sec
± 0.04 ¢ ± 0.15 ¢ ± 0.29 ¢
Comparable to values measured during 1993 restart
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UNCLASSIFIED Slide 17
UNCLASSIFIED
Burst OperationBurst Operation
1 Move Control Rod 2 to 0 500”1. Move Control Rod 2 to 0.500 2. Find DC with Control Rod 13. Insert (or remove) burst increment with Control Rod 2
(nominally 95 mils for 70º burst 150 mils for 100º burst)(nominally 95 mils for 70º burst, 150 mils for 100º burst)4. Retract safety block 2-5 inches5. Unlock 3rd burst button, enter BURST OPERATIONS6 Wait 15 20 minutes for delayed neutron decay6. Wait 15-20 minutes for delayed neutron decay7. Arm instrumentation, Ocilloscope, trigger module8. Insert safety block 9 Immediately insert burst rod (requires both crew members)9. Immediately insert burst rod (requires both crew members)
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UNCLASSIFIED
UNCLASSIFIED
Safety Block Rate of ShutdownSafety Block Rate of Shutdown
40000
50000
60000
nter
s 1-
4
Safety Block Rod Drop Measurement
0
10000
20000
30000
Sum
of C
oun
0570 580 590 600 610 620 630
Time(s)
Shutdown Rate is approx. -$10/s
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UNCLASSIFIED Slide 19
UNCLASSIFIED
Control Rod CalibrationControl Rod Calibration
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UNCLASSIFIED Slide 20
UNCLASSIFIED
Worth of Burst RodWorth of Burst Rod
0.261 0.0301 $ 0.987 $ 0.992** $1 032
Burst Rod Worth
$1.032
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UNCLASSIFIED Slide 21** $0.04 Adjustment
UNCLASSIFIED
Burst ReproducibilityBurst Reproducibility
Establish DC Establish DC
Remove burst increment
Remove SB
Remove burst increment
Remove SB
Wait
Insert SB
Wait
Insert SB
Insert BR/burst
BR out
Insert BR/burst
BR out
Repeat Repeat
90.69 ± 0.13 ¢ 90.19 ± 0.03 ¢
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UNCLASSIFIED Slide 22
UNCLASSIFIED
Reactivity Quenching (Temperature Coefficient)Reactivity Quenching (Temperature Coefficient)
For characterization plan, we started on a positive period and showed that as temperature increased, period decreased.p , p A free run would also demonstrate a negative temperature coefficient. Enough variation in room temperature over characterization to plot excess reactivity versus temperatureexcess reactivity versus temperature.
19.0
20.0Reactivity versus Average Temperature
y = -0.4296x + 27.075
16.0
17.0
18.0
activ
ity (c
ents
)
- 0 4 cents/ºC
13.0
14.0
15.0
20 22 24 26 28 30
Rea 0.4 cents/ C
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UNCLASSIFIED Slide 23
Temperature (deg C)
UNCLASSIFIED
Approach to PromptApproach-to-Prompt
Perform successively larger burstsMost accurate determination of rod worth
99.3 ¢
98
99
100
Most accurate determination of rod worth Demonstrates process
95
96
97
vity
(cen
ts)
92
93
94R
eact
iv
90
91
-350 -300 -250 -200 -150 -100 -50Burst Increment (mils)
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UNCLASSIFIED Slide 24
Maraging Steel Clamp
Steel Loading Ring
Anti-Rotation Bolt9/16” X 4 3/8” Glory Hole Mandrel
Maraging Steel Compression Ring
RTD
Locking Bolt
Steel Support Pad
Safety Block
Support Leg
Burst Rod
RTDSafety block mandrel
Upper Support Plate
Attachment Bolts