Gamma Scan Validation of SIMULATE5 BWR Model Features

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Gamma Scan Validation of SIMULATE5 BWR Model Features

2009 European Users Group Meeting

Chester, UK September 16-18 2009

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2009 User‘s Group Meeting September 2009, Chester

Overview

• SIMULATE5 Models Specific to BWR

– LPRM Tube Modeling

– Intra-nodal Void Quarter-Bundle Thermal Hydraulic (QTH) Model

• LPRM Tube Model Description

• Intra-nodal Void Model

• Background on Hatch Gamma Scan

• Validation of LPRM Tube Model via Hatch Gamma Scan Results

• Validation of Intra-nodal Void Model via Hatch Gamma Scan Results

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LPRM Tube ModelingLPRM

Simplified LPRM

Pin Powers (No LPRM) Pin Powers (LPRM) Difference *100

1.12 1.13 1.0

0.97 1.11 0.98 1.12 0.8 0.9

1.09 0.97 1.08 1.09 0.98 1.09 0.9 0.7 0.6

1.02 1.16 0.97 0.89 1.02 1.16 0.98 0.90 0.8 0.7 0.5 0.2

0.99 1.10 0.90 0.86 0.89 1.00 1.11 0.90 0.86 0.88 0.6 0.6 0.3 0.0 -0.3

1.14 1.12 0.40 0.88 0.95 1.05 1.14 1.13 0.40 0.88 0.95 1.03 0.6 0.5 0.2 -0.2 -0.9 -2.0

1.13 1.01 1.11 1.07 1.12 0.94 1.08 1.13 1.01 1.11 1.07 1.11 0.91 1.02 0.6 0.4 0.2 -0.4 -1.5 -2.7 -6.0

LPRM Tube, which has significant impact on N-N corner pin,

is modeled explicitly in SIMULATE-5

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Improvements:BWR Quadrant-Assembly TH (QTH)

• Performed after conventional TH calc.

• Input:

- Total assy inlet flow rate

- Quadrant-power from radial submesh calc.

• Output:

- Quadrant-assy flow, void, ...

- Density feedback to radial submesh XS

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Improvements:BWR Quadrant-Assembly TH (cont.)

3 options:

1. Non-communicating Q-channels (eg. SVEA)

- Flow from total axial pressure drop equalisation

2. Cross Flow I

- Lateral momentum equation

- Turbulent mixing and void drift neglected

3. Cross Flow II

- Continuous pressure equalisation in z-direction

- Fast convergence

pax

plat

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Void and power in 4 BWR Sub-Channels

0

50

100

150

200

0 5 10 15 20 25

z

NW

SE

NW

SE

0

20

40

60

80

0 5 10 15 20 25

z

SE

NW

POWER VOID

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Skewed void impacy on pin powers

Difference (Skewed void) – (Flat void) (%)

-8

-4

0

4

8

12

0 5 10 15 20 25

Max pin

Pin (1,1) - CR

Pin(8,8) - Det

Avg pin

z

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Hatch 1 Gamma Scan Background

• Extensive Gamma Scan Measurements following Cycles 1 & 3

• 106 Bundles were Scanned Following Cycle 1 (EPRI NP-511, August 1978)

– 35 Controlled bundles

– 71 Uncontrolled bundles

– 4 Bundles were disassembled for Rod Scanning (40 out of 49 rods)

– 1 Deep controlled (notch 14) Bundle HX0373

– 1 Shallow controlled (notch 34) Bundle HX0393

• 126 Bundles were Scanned Following Cycle 3 (EPRI NP-2105, August 1978)

– 14 Controlled bundles

– 112 Uncontrolled bundles

– 3 Bundles (7x7) were disassembled for Rod Scanning (40 out of 49 rods)

– 1 Bundle (8x8) were disassembled for Rod Scanning (54 out of 62 rods)

– 1 Shallow controlled (notch 34) Bundle HX0260

• Analysis of the Rod Scanned Bundles was the Primary Focus of the

benchmarking

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Hatch 1 Cycle 1

Gamma Scan Bundle LocationsHX0373

HX0393

HX0169

HX0141

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Hatch 1 Cycle 3

Gamma Scan Bundle location

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Gamma Scanning Calc. in SIMULATE-5

• Gamma scanning analysis built into SIMULATE-5

Ba140 is tracked explicitly per pin (as well as per node)

is solved to give

• The half life of Ba140,Ba140, is 12.8 days, the tracking starts at least 2000 hours before

the gamma scanning takes place. The initial condition is that the Ba140 concentration is

in equilibrium.

• The fission yield for Ba140, iBa140, per pin is calculated from CASMO-5 and tabulated in

CMS-Link library.

iBa

G

g

gigif

Ba

i

i Ndt

dN140

1

,

140

140 140

140

,

1140

( ) (0) 1Ba Ba

Ba Gt ti

i i f gi gi

gBa

N t N e e

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Effect of LPRM Tube Modeling (Uncontrolled HX0038, Cycle 3)

SIMULATE5 With QTH & Without LPRM Tube Modeled

SIMULATE5 With QTH & LPRM Tube Modeled

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Effect of LPRM Tube on NNC Rod Power

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Effect of LPRM Tube Model on WWC & NNC Rods

in HX0373 Cycle1

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Effect of LPRM Tube on NNC Adjacent Rods (Average Power)

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Effect of QTH Model

(Deep Controlled Bundle HX0373, Cycle 1)

SIMULATE5 With QTH & LPRM Tube Modeled

SIMULATE5 Without QTH & LPRM Tube Modeled

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Effect of QTH Model on WWC Rod Relative Power

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TIP Comparison Near Bundle HX0373

Calculated result overpredicts

by >10% at peak

Dominated by NNC pins

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Effect of QTH Model on WWC Rod(Deep Controlled Bundle HX0373, Cycle 1)

Underprediction of ~25% at

peak at WWC (NO QTH)

QTH improves by ~9% at peak

at WWC

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Effect of QTH Model on WWC Rod(Deep Controlled Bundle HX0373, Cycle 1)

Pin normalized results

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Effect of QTH Model on NNC Rod(Deep Controlled Bundle HX0373, Cycle 1)

Behavior for NNC consistent

with TIP error of ~10%

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Effect of QTH Model on WWC & NNC Rods in

HX0373 Cycle1

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Summary

• SIMULATE-5 accurately predicts the pin Ba-140 number densities

(and therefore pin powers)

• The LPRM tube impacts the corner and surrounding pins in the NNC.

This appears as a systematic bias (overprediction) of pin powers

(~5% in the corner). SIMULATE-5 explicitly models the LPRM tube

as a branch case in the cross section library and pin reconstruction.

• Quarter-assembly T-Q (QTH or skewed void) model impacts cases

of deep control rod insertions, where extreme power and void

gradients (>40%) are observed. Improvements of ~9% are observed

in WWC pins for an assembly with deeply inserted control rod

although peaking results were still underpredicted.

• Further refinements of sub-channel T/H model continues with focus

on consistency between neutronic and T/H submesh.

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Gamma Scan Validation of SIMULATE5 BWR Model Features

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