ML22269A388
| ML22269A388 | |
| Person / Time | |
|---|---|
| Site: | Oconee, La Crosse File:Dairyland Power Cooperative icon.png |
| Issue date: | 09/07/2022 |
| From: | LaCrosseSolutions |
| To: | Office of Nuclear Material Safety and Safeguards |
| Shared Package | |
| ML22269A395 | List: |
| References | |
| LS-2022-0019 | |
| Download: ML22269A388 (3) | |
Text
GammaSpectroscopyofConcretePucks
==
Introduction:==
LacrossedecommissioningstaffanalyzedcharacterizationandFSSconcretepucks(3indiaX0.5inthick) usingtheinhousegammaspectroscopysystem.Foreachpuck,ananalysiswasperformedoneach facingsurfaceincloseproximitytothedetector.AsummaryofthedataisshowninTable1.
Table1:SummaryofPuckOnsiteAnalysis SampleID Orientation Cs137Results, (pCi/g)
Ratio top/bottom B101004ACJFC009CV00.5" Top 5.95 2.20
Bottom 2.70
B101004ACJFC010CV00.5" Top 10.5 1.72
Bottom 6.11
B101004ACJFC011CV00.5" Top 4.63 2.91
Bottom 1.59
B101004ACJFC012CV00.5" Top 3.16 3.58
Bottom 0.882
B101004ACJFC013CV00.5" Top 148 2.92
Bottom 50.7
B101004ACJFC014CV00.5" Top 74.2 3.27
Bottom 22.7
B101004ACJFC016CV00.5" Top 5.48 2.67
Bottom 2.05
average 2.75
Inordertoassessthedistributionoftheactivity,asimulationwasdoneusingMicroshieldforseveral geometricalrepresentationsofactivitydistributionforacomparisontotheratiosinTable1.
Analysis:
TwoMicroshieldmodelswerecreatedforthissimulationaspresentedbelow.
Model1:
Thismodelvariedthethicknessoftheactivitydistributedwithinthepuckfromathicknessof0.25mm to10mmandforeachthickness,theactivityremainedat320µCi(1Bq/gfor1mmthicksource).For eachcase,thedosepointwasatthepuckcenterwithanoffsetof1cm.ThisdataisshowninTable2.
Table2:DosePointatCenterof3inchdiametersourceatanoffsetdistanceof1cmfromthesource.Diskactivityat320µCiCs 137,variablesourcethickness Case Source Thickness(mm)
BackSideDose Rate(mR/h)
FrontSideDose Rate(mR/h)
Ratio:
Front toBack 0.25mmSource 0.25 6.26E05 1.79E04 2.86 0.50mmSource 0.50 6.30E05 1.75E04 2.78 0.75mmSource 0.75 6.37E05 1.73E04 2.72 1mmSource 1
6.44E05 1.71E04 2.66 2mmSource 2
6.66E05 1.61E04 2.43 3mmSource 3
6.89E05 1.53E04 2.23 4mmSource 4
7.17E05 1.47E04 2.05 5mmSource 5
7.44E05 1.41E04 1.89 6mmSource 6
7.69E05 1.35E04 1.75 7mmSource 7
8.10E05 1.30E04 1.60 8mmSource 8
8.42E05 1.25E04 1.48 9mmSource 9
8.79E05 1.20E04 1.36 10mmSource 10 9.23E05 1.16E04 1.26
Figure1
ThisdatastronglysuggeststhattheobservedratiofromTable1of2.75suggestsaverythinsource distributionofapproximately1mmorless.
Model2:
Thismodelassumedthatthesourcewasdistributedina1mmlayerintwoconfigurations,thesource facingthedetectorandthesourcefacingawayfromthedetector(gammaraysattenuatedthroughthe 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 0
1 2
3 4
5 6
7 8
9 10 11 ActivityRatioFronttoBack SourceThickness(mm) 137CsActivityDepthRatio (constanttotalsourceactivity,nobuildup)
0.5inchconcretepuck).Inthiscase,a1CiCs137sourcewasusedforallrunsandthegapbetweenthe concreteandthedosepointswas0.3mmairandthelocationvariedradiallyfromthecentertothe edgeinfourincrements.ThedatafromtheseanalysesareshowninTable3andsupportthehypothesis thatthesourceisthinsincetheratiosshownbelowareclosetothevaleof2.75fromTable1 Table3 1mmDiskSourceThickness,offsetdistanceof0.3mm RadialDistance, cm DRSource Awayfrom Detector(back),
R/hperCi DRSource Towardsfrom Detector (front),R/hrper Ci Ratio:Frontto Back 0
478 1489 3.12 1.27 459 1439 3.14 2.54 390 1309 3.36 3.81 253 681.4 2.69
Conclusions
TheMicroshieldmodelsstronglysuggeststhatthedistributionofCs137issubstantiallysmallerthanthe valueof0.5inchusedintheWGTVISOCSmodeling.