Hanford Waste Tank. Cone Penetrometer. CElV WHC-SA-3023-FP. Westinghouse Hanford Company Richland, Washington

Transcription

1 ~~~ ~ ~~~ ~~ ~~ -- WHC-SA-3023-FP Hanford Waste Tank Cone Penetrometer CElV Prepared for the U.S. Department of Energy Assstant Secretary for Envronmental Management Westnghouse Hanford Company Rchland, Washngton Management and Operatons Contractor for the U.S. Department of Energy under Contract DE-AC06-87RL10930 Copyrght Lcense By acceptance of ths artcle, the publsher and/or recpent acknowledges the U.S. Government's roht to retan a nonexclusve, royalty-free lcense n and to any copyrght coverng ths paper

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3 W H C -SA F P Hanford Waste Tank Cone Penetrometer R. Y. Seda Date Publshed December 1995 To Be Presented at Socety of Hspanc Professonal Engneers (SHPE) Eghteenth Annual Natonal Techncal & Career Conference (NTCC96) Seattle, Washngton February 15-17, 1996 Prepared for the U.S. Department of Energy Assstant Secretary for Envronmental Management Westnghouse P.0 Box 1970 Hanford Company Rchland, Washngton Management and Operatons Contractor for the U.S. Department of Energy under Contract DE-AC06-87RL10930 Copyrght Lcense By acceptance of ths artcle, the publsher and/or recpent acknowledges the US. Government's rght to retan a nonexclusve, royalty-free lcense n and to any copyrght coverng ths paper. Approved for publc release

4 LEGAL DSCLAMER Ths report was prepared as an account of work sponsored by an agency of the Unted States Government. Nether the Unted States Government nor any agency thereof, nor any of ther employees, nor any of ther contractors, subcontractors or ther employees, makes any warranty, express or mpled, or assumes any legal lablty or responsblty for the accuracy, completeness, or any thrd party's use or the results of such use of any nformaton, apparatus, product, or process dsclosed, or represents that ts use would not nfrnge prvately owned rghts. Reference heren to any specfc commercal product, process, or servce by trade name, trademark, manufacturer, or otherwse, does not necessarly consttute or mply ts endorsement, recommendaton, or favorng by the Unted States Government or any agency thereof or ts contractors or subcontractors. The vews and opnons of authors expressed heren do not necessarly state or reflect those of the Unted States Government or any apencv thereof. Ths report has been reproduced from the best avalable copy. Prnted n the Unted States of Amerca DSCLM-2.CHP (1-91)

5 . HANFORD WASTE TAHK COWE P %ZTROH,ET~ R,Y- Seda, Westnghouse Hanford P-0- Bux 1,970, HSW s-09, Rchland, WA ABSTlUHX A new toof s beng developed to characterze tank waste at the kanford Reservaton. Ths tool, known as the cone penetrometer, s capbble of obtanng chemcal and physcal propertes n stu. For the past 50 years, ths tool has been used extensvely n sol applcatons hand now has been modfed for usage n Hanford Underground Storage tanks: These modfcatons nclude development of new "wasterf data models as,well as hardware desgn changes to accommodate the hazardous and radoactve envronment of the tanks. The modfed cone penetrometer s schddule to be deployed at Hanford by Fall At Hanford, the cone penetrometer wll Se used as an nstrumended ppe whch measures chemcal and physcal propertes as t pushes through tank waste. Physcal data, such as tank waste stratfcaton and mechancal propertes, s obtaned through three sensors measurng tp pressure, sleeve frcton and pore pressure. Chemcal data, such as chemcal specaton, s measured usng u Raman spectroscopy sensor. The sensor package contans other nstrumentaton as well, ncludng a tp and sde temperature sensor, tank bottom detecton and an ncldometer. Once the-cone penetrometer has reached the bottom of the tank, a mosture probe sll be nserted nto the ppe. Ths probe s used to measure waste mosture content, water level, waste surface mosture and tank temperature. Ths paper dscusses the development of ths new measurement bystem. Data from the cone penetrometer wll ad n the selecton of damplng tools, waste tank retreval process, and addressng varous tank safety ssues. Ths paper wll explore varous waste models as well' as the challenges assocated wth tank envronment. EACXGROUND NTRODUCTON Hanford was the ste of a weapons grade plutonum producton pladt bult durng World War 1 as part of the Manhattan project. Snce the plant stopped producton n 1989, the msson at Hanford has shft'ed from weapons producton to cleanng up the waste generated from such actvtes. The by products from the generaton of weapons were stored n 149 sngle shell tanks and 28 dauble shell tanks. These, tanks, located underground, were bult to hold over mllon gallons of hazardous and radoactve waste. Some of these tanks are as large 8s 70 feet n dameter and SO feet n depth. Over tme, some waste by- products have been reprocessed to reduce ther volume, thus ncreasng the avalablty of tank storage room. Even though records were 1

6 mantaned on the materals orgnally stored n these tanks, the/ actual chemcal/physcal composton s mostly unknown. ~ Several methods are beng mplemented to characterze these unknown waste compostons, ncludng core samplng and the use of bn-tank nstrumentaton. Drllng core samples from the contents of the tank and sendng these samples to laboratores for analyss s the standard method for obtanng certan chemcal and physcal data. kn-tank nstrumentaton ncludes systems whch gather temperature lqud level and other measurements. Unfortunately no sngle method can ob+n all the nformaton requred for safely remedatng the tank waste.! Snce no one method s avalable, several methods are beng consdbred to obtan all the needed data. One of the most promsng methods Wes the cone penetrometer to obtan chemcal and physcal propertes d&a- WSTRUnarr GENERAL QESCRPTOX The cone penetrometer conssts of an nstrumented metal rod whch s pushed through a materal. The rod s supported by a gude provdes structural support to the rod. The rod s screvnq hollowed rod sectons nto the nstrumented tp a6 t s pushed, and penetrates the materal. The basc nstrument /package conssts of sensors to measure tp pressure, pore pressure and! sleeve frcton. Load cells at the tp (tp pressure) measure resshnce of the materals ahead of the tp whle sde load cells (frcton sleave) measures the frcton as the cone pushes nto the materal. Elfltered hydrostatc pressure (pore pressure) s obtaned usng a sensnq devce also located wthn the tp. Classfcaton charts are then gelnerated by measurements taken from these three sensors. These charts are typcally used to determne the type of sol or materal! beng penetrated- Fgure 1 dapcts a typcal data plot generated frod a push through dfferent sol types, Other devces may be attached to the basc cone repackagng the tp, lowerng another sensor down nto the rod, of by a specal rod tp. Many n-stu sensors are already avalable for the cune penetrometer, sensors to measure temperature, shear modul48, sol densty, vslcosty, ph, chencal speces, mosture, radaton, hydrocarbon dnd resstvty. Resstvty measurements are baed to determne the locaton and depth of groundwater. The resstvqy probe has tvo electrodes mounted on an nsulated sleeve above the cone. These two electrodes measure sol conductvty (resstvty) by paskng an electrcal current between them. Snce mneralzed water ks very conductve, the sensor s deal for locatng water. Sol, gas aqd water samplers can also be attached to the rod by unscrewng the tradtonal tp and replacng t wth a sampler tp. Orgnally, cone penetrometers vere developed for sol applcatgns such as locatng frmer sols n sea locked countres lke the Netherlands. Snce then, cone penetrometers have been used n sol dentdcaton, sol physcal parameter determnaton, accessng sol bearng caqactes 2!

7 ~ Hanford and ste characterzaton. Modern versons have the addtonal capacty of measurng physcal and chemcal characterstcs wthout removng samples from the ground. Other capabltes nclude groutfng of boreholes produced after samples have been taken. Crout$ng the boreholes s necessary to avod ntroducng contamnants from the surface to possble aqufers. BODY Hanford tank waste s a mxture of sludge and saltcake materalk. The skd mounted cone penetrometer system wll be capable of penetratng these tank waste materals to obtan physcal and chemcal data. Sludge waste s a very weak materal whle saltcake vaste can be very hard. The data whch wll be obtaned by the cone peneqometer ncludes: shear strength, compressve strength, yeld stress', waste stratfcaton, chemcal specatons, and mosture. These Perved measurements are n adhton to the drect measurements of tp stress, sleeve frcton, pore pressure, tp and sde temperature, nclhaton, bottom detecton, and waste tank temperature. Fgure 2 shows a schematc of the probe. Shear strength, compressve strength and yeld stress are Ghyscal propertes needed for the safe retreval of tank waste. Knowdedge of waste stratfcaton profles wll ad other exstng samplng dools n the tanks snce t dentfy the materal penetrated. Fr6m ths nformaton, the approprate samplng mode can be selectedt The samplng modes nclude the usage of auger, push mode or rotary core samples. The "hardness" of the sampled materal can affect the recovery rate of these systems. Chemcal specaton data wll be bed to determne the waste compatblty ssues durng the retreval/prucessng of the waste. Mosture and tank temperature are requred to ansver many tank safety questons. The operaton of the skd mounted cone penetrometer s straght4orward. As the tp of the cone penetrometer s lowered nto the tank, nformaton about chemcal and materal propertes wll be sent'back to an on-board computer and analyzed. The computer, as well as the sgnal condtonng and processng equpment, s located n specally desgn skd on the tank. OnC8 the tp reaches the desred locaton n 'a tank, such as the tank bottom, cables leadng to the sensors n the t!p wll be removed to allow room for other nstruments. A mosture sengor, for example, can be lowered vth a wnch to obtan the mosture content of the surroundng tank waste materal. Once all data have been obtaned, the cone penetrometer rod s removed from the tank.! Hanford tank waste presents an unusual challenge to nstruments lke the cone penetrometers. Tank nterors can only be accessed through rsers protrudng out of the top of the tank. Rsers are ppes whch are used to reach the tank nterors. Tank contents are not easy to samp4e snce 3

8 the waste contaned w t h n the tank s both hazardous and r a d o h v e. As the cone p e n e t r o m e t e r lowers ts rod and gude tube down thej rser, they wll be unsupported untl the waste s reached. The gube tube wll provde structural support to the push rod as the push rod Due to the possblty of bucklng, o & r a t n q penetrates t h e waste. loads wll be lmted after completon of stress analyss and s t r, u c t u r a l testng completon. n typcal sol applcatons, the s o l bsually supports the cone and rod as t s lowered. Other challenges pertan to t h e tank structure tself. T h e tank tops have lmts to ther Load capactes. Cone penetrometers acheve the necessary reacton force to push the rod down nto the sol by ether anchorng the cone penetrometer support s t r u c t u r e n the surroundng sol or by ballastng the support structure w t h t h e necessary ;weght.snce anchorng the cone penetrometer support structure onto thetank s n o t f e a s b l e, ballastng weght on the skd must be used to achkeve the necessary reacton force to penetrate the waste wthn the tank. Ths reacton force s lmted by the total weght whch the top of?he tank can wthstand wthout falure. Dome loadng lmtatons a t,hanford tanks v a r e s dependng on the equpment loadng and sol loadqg. The maxmum reactve force whch the cone penetrometer wll be ca@ble of e x e r t n g on t h e tanks Wll be 30 tons. Another structural problem unque to t h e tanks s how to determne where the locaton of the bottom of the tank. Snce chemcal reactdns have occurred wthn the Hanford tanks f o r decades, the bottom of the tank may be bowed due to t h e hgh h e a t assocated wth the reactond of the waste. Tank b o t t o m s have a l s o corroded wth tme. To cornpendate for these problems, an operatonal envelop lmtng t h e forces apdled to t h e b o t t o m of the t a n k as well a s a bottom detecton systom are beng developed. The cone penetrometer bottom detecton systen s a magnetometer sensor whch wll stop the rod once t h e sensor has detected the bottom of the tank. The magnetometer detects t h e tanks [ferrous materal. Test ndcate that t h e bottom of the tank can be 4easured wthn a feet of a s t e e l plate. The closer t h e magnetometer s to the steel bottom, t h e stronger the sgnal. Ths new sensor $as the potental of beng used n other applcatons such as l o c a t n g p p e s and other ferrous structures n the sol applcatons. DATA XODELS! j Snce the cone penetrometer has never been tested n Hanford type waste, waste smulants were developed to smulate the materals n t$e tank, such as s a l t cake and sludge. Tank waste mechancal propertks were determned by emprcal formulatons based on sol theory. W r each smulant, a waste classfcaton chart was developed as a cal3braton gudelne f o r f u t u r e usage to determne what knd of the materal the cone penetrometer vas penetratng. O t h e r data obtaned durng smulant testng ncluded pushng requrements of the system. Salt cakes and sludges are the major components of 4 the tank waste.

9 Salt cake can be hard as cement whle sludge can have the conssqency of clays. The cone penetrometer must penetrate through both of these components to gather data on physcal propertes. The physcal propertes of nterest were sludge yeld strength, sludge shear skrength and saltcake compressve strength. These measurements were obtaqed from tp pressure, sleeve frcton, and pore pressure sensors. ', Waste classfcaton charts were developed and are depcted n the Apj?endx. 1 The physcal propertes sol models used to develop the corrdlatons between mechancal propertes and the cone penetrometer sensor readngs were based on the sphercal cavty model- Estmates for the1 sludge shear strength employed the followng equaton: 'peak = ( q, - Q"., 1 / N, where 4% = cone bearng (bearng force/bearng area) = "0 - overburden pressure (densty of the materd1 tmes the depth). n materals wth 3 ps or less of shear strength, pore pressure over df fdrental depth can be used. Cone factor (generally obtaned from e,prcal d Nk, - correlatons). n clays, t s normally between 10 and 20 The emprcal correlatons based on the test results were the fol'lowng: Yeld strength Shear strength Compressve strength These models were only vald for the smulants tested- The sdmulants were two clays for sludges (Kaoln and Bentonte) and KSMag (a fertlzer or cattle supplement) or saltcake, All these materals are non-hazardous. Further testng wll be completed so that the dfferent waste types are classfed and the accuracy of the nstrument s accessed. The test results ndcate that the srnulants occuped dstfnctde areas n the uaste classfcaton charts. The appendx shows the df 4erences n the tp stress profles and sleeve stress profles. A prelmnary waste classfcaton chart has been created n whch the weak 'sludges and strong saltcakes are dsplayed. rnsturb PROBE The mosture probe s lowered n the cone penetrometer push rod nner dameter and programmed to automatcally take readngs every nc for 10 to 50 seconds. The testng results have shown that the sumo 9 ndng 6 nches of materal can be effectvely measured. The technque'used to measure mosture s through neutron thermalzaton. Ths technques has 5

10 been used n other appl-catons to measure mosture on s o l surfce and wthn ol-loggng holes. Neutrons are emtted by a sourc8,: Cf-252 source, n t h s case, onto the materal of nspecton. The source neutrons scatter and lose some energy. Neutrons lose nost of t s ] energy when scatterng from a hydrogen nucle (proton) because t has *&e same mass. Neutrons scatter several tmes and eventually slow down to thermal energes. A thermal neutron senstve detector, located near the neutron source, d e t e c t s source neutrons whch become thermalhzed by the hydrogen w t h n the waste and scatter back t o the d e t e c t o r. The more water present, the more hydrogen and the greater t h e count Zate n the thermal n e u t r o n detector. The count rate s correlated to mbsture c o n t e n t n waste materal. Ths technque s senstve to t h e adount of hydrogen n w a s t e, t s also senstve to the amount of organc whl.ch contan hydrogen. CONCLUSON The cone penetrometer s scheduled to be deployed n the Hanfodd waste samplng process n Ths system wll jon several other mdasurng systems currently beng used to CharaCterZ8 tank waste. Cone penetrometer usage n the tanks represents a new applcathn that devates from t s tradtonal uses n s o l analyss. For tan* waste, the cone penetrometer wll acqure physcal and chemcaz waste propertes requred for remedaton and processng as w e l l 'as t h e resoluton of tank s a f e t y questons.! ACXN~E34EWP! would lke to acknowledge my husband, John Blyler, for h s sudport n the development of ths paper. REFERENCES W.L. Bratton, D.E. Chtty, S. P. Farrngton, ARA Report No , "Development of correlatons between cone penetrometer testng lresults and physcal and mechancal propertes f o r Hanford saltcake dmulant materals'q, August W.L. Bratton, D.E. Chtty, M. Gldea, ARA Report , ttdevelobment of correlatons between cone penetrometer testng results and physcal and mechancal p r o p e r t e s : orhanford sludge smulant materalsn, June P. R. Robertson, R. G. Campenella, "Gudelnes f o r Geotechncal. Desgn usng Cone Penetrometer T e s t s and CPT wth pore pressure measurmentsn, November cone bearng NOHENCATURE averburden pressure 6

11 Cone factor Yeld strength Shear strength Compressve strength 7

12 APPENDX 8

13 e h ' l L) 0) 2 25! 0. 0!; 10! U f Sloovo Frlctloc Tp Frlctlor The (nn) POfQ Pore Pressure Dsspaton Tests.._ ~ - Fgure 1: Typcal Sol Cone Penetrometer Data 9

14 l- Mosture Probe Sde Temperature Sensor Sleeve Load Cell Tp Temperature Gage Pore Pressure Gage F rcton Sleeve Bottom Detector 7 Fgure 2: Cone Penetrometer Sensor Tp Schematc O

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