godiva core assembly and startup for ncsp review-unclassified · 2017-10-20 · godiva assembly...

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


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



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.



UNCLASSIFIED

Upper Fuel AssemblyUpper Fuel Assembly

Thicker shim ring constructed to gcompensate for fuel lost over time.



UNCLASSIFIED

Upper Fuel Assembly (continued)Upper Fuel Assembly (continued)

Load bearing steel ring placed on top of fuelg g p p



UNCLASSIFIED

St k th L CStack the Lower Core

1 2

3 4

Alignment ofAlignment of grooves absolutely essential



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.



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.



UNCLASSIFIED

Install the Support LegsInstall the Support Legs

Core is suspended while legs p gare attached.



UNCLASSIFIED

Install the Saturn RingInstall the Saturn Ring

Bolts are tensioned outward. Measuring and adjusting for g j gequal distance to ensure even tension.



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.



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.



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


UNCLASSIFIED Slide 14Slide 14

UNCLASSIFIED

Approach to CriticalApproach to Critical

1/M on Safety Block position

1/M on Sum of Control Rod positions



UNCLASSIFIED

First Critical at DAFFirst Critical at DAF

Excess reactivity $1.07 compared to $1.23 prior to disassembly



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



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)


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



UNCLASSIFIED

Control Rod CalibrationControl Rod Calibration



UNCLASSIFIED

Worth of Burst RodWorth of Burst Rod

0.261 0.0301 $ 0.987 $ 0.992** $1 032

Burst Rod Worth

$1.032


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 ¢



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



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)



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

godiva core assembly and startup for ncsp review-unclassified · 2017-10-20 · godiva assembly...

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