Baseline Neutron Logging Measurements in the Drift Scale Test

Transcription

1 UCRL-ID Baseline Neutrn Lgging Measurements in the Drift Scale Test W. Lin R. Carlsn D. Neubaurer January 1998 Lawrence Livermre Natinal Labratry This is an infrmal reprt intended primarily fr internal r limited external distributin. The pinins and cnclusins stated are thse f the authr and may r may nt be thse f the Labratry. Wrk perfrmed under the auspices f the U.S. Department f Energy by the Lawrence Livermre Natinal Labratry under Cntract W-7405-ENG-48.

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3 Baseline Neutrn Lgging Measurements in the Drift Scale Test Milestne SPY195M4 Wunan Lin, Richard Carlsn, and Dan Neubaurer Intrductin The Drift Scale Test (DST) is ne f the thermal tests being cnducted in the Explratry Studies Facility (ESF). One f the bjectives f the DST is t study the cupled thermal-mechanicalhydrlgical-chemical (TMHC) prcesses in the ESF at the repsitry hrizn f the ptential high-level nuclear waste repsitry in Yucca Muntain, Nevada. The bjectives, the test design, and the test layuts f the DST are included in the test design reprt by CRWMS M&O Cntractr [1]. The cnfiguratin f the DST includes a declining Observatin Drift driven mstly east and dwnward frm main tunnel in the ESF, at abut km frm the Nrth prtal. The dwnward slpe f the Observatin Drift (11.5 t 14.0 percent) ensures a minimum 10 m f middle nnlithphysal Tppah Spring Tuff as the verburden fr the DST. The length f the Observatin Drift is abut 136 m. At the elevatin f the DST crwn (nminally 10 m belw the upper extent f the middle nnlithphysal Tppah Spring Tuff) the Cnnecting Drift breaks ut t the nrth frm the Observatin Drift, 136 m frm the main tunnel f the ESF. The Cnnecting Drift extends apprximately 40 m t the nrth frm the Observatin Drift. A Heater Drift breaks ut westward frm the Cnnecting Drift at abut 30 m frm the Observatin Drift. The Heater Drift cnsists f an 11 m lng entry, which includes a platelading niche, and a 47 m lng heated drift. The nminal diameter f the drifts is 5 m. The detail cnfiguratin f the DST, including diagrams shwing the drift and brehle layut, is included in the test design reprt by CRWMS M&O Cntractr [1]. Thermal neutrn lgging is a methd used t determine misture cntent in rcks and sils and will be used t mnitr misture cntent in brehles ESF-HD-NEU-1 t ESF-HD-NEU-10 (Brehles #47 t 51 and 64 t 68), ESF-HD-TEMP-1 (Brehle #79), and ESF-HD-TEMP-2 (Brehle #80) in the DST. The neutrn prbe cntains a surce f high energy neutrns and a detectr fr slw (thermal) neutrns. Water present in rcks slws dwn the neutrns making them detectable (because f the presence f hydrgen). Thus, higher cunts (r a psitive difference in cunts relative t backgrund r pre-heat levels) indicate higher water cntent (r 1

4 increased water cntent ver backgrund). The prbe used in these baseline measurements is a Campbell Pacific Nuclear (CPN) mdel 503DR. The 3.81-cm (1.5 inch) diameter prbe was als utilized fr the Single Heater Test (Serial Number: H ). Under ambient cnditins the sampling vlume has a diameter apprximately 15 cm surrunding the prbe, increasing as misture cntent decreases. Measurements are sensitive t the presence f elements that have large neutrn capture crss-sectins, such as chlrine and brn. The uncertainty f the neutrn lgging is abut 3 t 5% in water cntent, by cnsidering the cunting statistics and ther uncertainties, such as lcatin f the tl. A new neutrn tl made by LND, Inc. (Mdel LND 25147) has been purchased fr measuring the neutrn cunts f the rck mass during the heating and cling phases f the DST. The LND tl is designed fr perating at temperatures t 200 C. Fr brehles ESF-HD-NEU-1 t ESF-HD-NEU-10 f the DST a Tefln tube was inserted int the brehles and gruted int place. The Tefln tube permits easy insertin, placement, and remval f the tl. Calibratin f bth the CPN tl and the LND tl in the Tefln-grut assembly identical t that used in the hles will be cnducted. Fr brehles ESF-HD-TEMP-1 (Hle #79) and ESF-HD- TEMP-2 (Hle #80) ne RTD bundle was attached t the utside f the Tefln liner, and the assembly was gruted in place in the hles. Calibratins f the neutrn tls in the Tefln liner-rtd-grut assembly identical t that used in the hles 79 and 80 will als be cnducted. The calibratin infrmatin will be used t cnvert the neutrn cunts reprted in this dcument int fractin vlume water cntent. Measurement Prcedures The fllwing prcedure describes the methd f cllecting the baseline neutrn data f the DST. We used the 3.81-cm diameter prbe (the CPN prbe) and a cunting time f 16 secnds. Standard cunts, which are the neutrn cunts when the tl is in the tl hlder away frm any influence f the rck mass t be measured, were measured and recrded immediately prir t, and subsequent t perfrming measurements. The neutrn prbe was placed in a brehle at a specific lcatin (depth) and the neutrn cunt recrded in a scientific ntebk as well as electrnically in the device memry. Upn cmpletin f the test, data was dwnladed t a cmputer and the data values checked against the hand recrded 2

5 values. Data were recrded at depth intervals f 10 cm in each brehle. The prcedures are described in TIP-NF-31 [2]. Tw baseline measurements were cnducted in each ne f the 12 hles after the hles were gruted. In Hle ESF-HD-TEMP-2 ne additinal measurement was cnducted befre the hle was gruted. The Baseline Data and Discussin The baseline neutrn cunts in the 12 brehles in the DST are shwn in Figures 1 t 12, fr brehles ESF-HD-NEU-1 t ESF-HD- NEU-10 and ESF-HD-TEMP-1 t ESF-HD-TEMP-2 respectively. Each ne f these figures presents the tw baseline neutrn cunts in the hle. In additin t the baseline neutrn cunts in Hle ESF-HD- TEMP-2, Figure 12 als shws the neutrn cunts in this hle befre it was gruted. The neutrn cunts f the tw baseline measurements in each hle agree well t each ther. The lw neutrn cunts at the cllar f sme f the hles (Figures 3, 4, and 11) may be influenced by the envirnment utside f the hle. They will be clsely watched during the lgging in the heating phase f the DST. Figure 12 shws that the deeper part f Hle ESF-HD- TEMP-2 (deeper than abut 52 m frm cllar) was nt gruted. Summary Successful baseline neutrn measurements have been cnducted in all f the neutrn hles in the DST. All f the baseline data have been presented in this reprt. These neutrn cunt data will be cnverted int the baseline water cntent f the rck mass when the neutrn tls are calibrated in the exact brehle cnfiguratin f the DST. Future Plans The DST prgresses int the heating phase. The neutrn lgging will be cntinued using the LND tl. During the first measurement using the LND tl, the CPN tl will als be used again t prvide a cmparisn f the neutrn cunts frm the tw tls. Calibratins f bth the LND tl and the CPN tl in the exact Tefln-grut and Tefln-grut-RTD assemblies, as used in the DST, will be cnducted. Then the baseline neutrn cunts and the future neutrn cunts during the heating phase will be cnverted int fractin vlume water cntents. 3

6 References [1]. Civilian Radiactive Waste Management System Management and Operatin Cntractr (OCRWM M&O), 1996a, Test Design, Plans, and Layut fr the First ESF Thermal Test, Rev. 1, BAB , TRW Envirnmental Safety System, Inc., Las Vegas, NV [2]. Lawrence Livermre Natinal Labratry Yucca Muntain Prject Technical Implementatin Plan, 1994, Neutrn and Gamma (Density) Lgging in Welded Tuff, TIP-NF-31, Riv. 1, Lawrence Livermre Natinal Labratry, University f Califrnia, Livermre, CA

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18 Technical Infrmatin Department Lawrence Livermre Natinal Labratry University f Califrnia Livermre, Califrnia 94551