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The original document from which this microfiche has been prepared has these imperfections: { I Missing pages/figures numbered: j | wrong pagination poor overall printing quality INIS Clearinghouse IAEA P.O. Box 100 cut text A-1400, Vienna AUSTRIA | |other irJIS-mf--11156 /^""- --•"''• •? r.-~j -. •*•. t *•= f j-'-. y :,/. !:"T5 ••'"•% /^ / r.,\ Li JuJv I-"'3<S i 841-302 In t.rcd:.'.c(" i or: The Nation.-.) Uranium Tnilinyr: Program has ccra .issioned a study to c-vfllyatc flexible membrane liners (gr.-ornerr.branes) as long-term barriers for Canadian uranium mill. taiJ i;:go. Colder Associates, together with their subconsultants Ontario Research Foundation and SErtE.S Consultants, have been retained by Supply and Services Canada to carry out Phase I of the study. This study reviews the common liner types and addresses flexible liners (polymeric membranes and asphalt) in detail. are reviewed. Conceptual designs are presented for basins to aceonuuodate 20 years accumulation of uranium tailings from mills in Klliot hakd and southeastern Athabasca. The study concludes with an outline of a proposed Phase II test program to carry out a detailed laboratory evaluation of candidate materials. Lincr Typoa Nine polymeric and three asphalt liner types have been considered with xe.opuct t.o the physical and chemical environment in the uranium producing areas of Ci-wiada. 7*11 materials indie a': c g a o d c h •?. r:. i c a 1 i •?.~ i r~ t •? p. z e to vi r a n: um wantos but are subject, fio installation p July 19S-'. j; 3<l-2o:r-- Tfia liner typor. cc:!-jic:crc:d £?:c: 1. roiyovhylcnr (i.\-.:* 2. High iK-.ii-iiy Polyothy.' cne (III'?1;; 3. Chlorinated Poly.?thy3 ane (CPE) 4. Chloro:j\ilp;ionatod Polyethylene (CSV") 5. Polyvinyl Chloride (PVC) 6. Ethylene Propylene Diene Monomer (XPDK) 7. Butyl Rubber 8. Polychioroprene (CR) 9. Polyurethane 10. Asp I .ait Emulsions 11. Catalytic Airblown Asphalt 12. Asphaltic/Elastomeric Compounds Surface sealants, including asphalt, show very low laboratory permeabilities but are subject to variable rates of application, are difficult to inspect during installation and are susceptible to damage duo to differential movements, equipment traffic and cyclical cJirnate effects including freeze-thaw cyclic loading. Asphaltic membranes must be provided with a soil cover. Polymeric novnbranes offer wide ranging chemical resistance and are readily inspected. However, they are susceptible to damage during installation largely oue to improper subyrade preparation and vehicular trairic. They require verv careful i nstaI 1 «i" i.nrx ;->.r\i\ r.reir pnrforninnco i r? dpp-'-nder.t on careful arid succt'&Kfu •. fi^IJ s;-jr,i:L.Kj. P.icl;i s*;vu.'..i i*q is, in <":crerc>l, a dct«iilo.''. cind "^"f.i..<:••. vo oror::•.*:; or.. V7;~.il:hrr, .inolud.irjy t^^poraturc and procipi'i.^l.i-':;-:, in gen; rally t!i;: governing factor. In this regarct, the olsato-.ifiric liners corssiderred in cr.is study, »eun«jly, Butyl, Polynhloropr«ne and EPDM would t'ppcir to present the xaoat pxohlcms in field JL-.1V It-*' iii L'42-3015 r.c.:ur..i.r.g. Oi the: rcv.-.airuri' li'/:-x. ty^-Ji; c.'nsi^ercd, success- ful fic-iu r^a-uin? h.v; b-er, ;'<• ••••-.;-. -ci; J., •" :nt\: l.DV<-:, i~, C5VZ, CPE P.n-.l PVC. It i..- .-ic'cd r-,-''ver, \_:\.-><- '':cro ,,r;: snrio'ir- T.L-. cKcul tiic ionc;-tci.:.". •...?j.L.*:-.;r:.i:.,; ; j.'. y of T'\'C t'.iicx TV.. There art: no st,ar.diirdi.:t:d n<.U."-rial &;.•.-'CJ fications for polymeric or asph.aitic i:ie.T.brane linnj:^ in either Canada or tlie U.S.A. HovttiV'ir, recently developed documents by the National Sr.Nation Foundation (NSF) offer some proirise of standardization. It is recomin.endad that the r.'SF standards be used when specifying minimum material properties. Liner Environment me environment in wnicn the caiiings nasins are constructed is an important aspect of liner toquireir.ents. Tailings basins in Elliot Lake and southeastern Athabasca would typically be situated in topographic lows with groundwater levels at or near ground surface, Sites would typically be underlain by organic matter, soils of moderate permeability and moderate to low permeability bedrock. A significant chemical characteristic of the Elliot Lake uranium tailings leachate is the potential for oxidization of; sulphide bearing minerals and the generation of sulpha-te rich, acidic porewater. As a result,- the porewater could contain some dissolved radionuclides and heavy metals from the tailings. Liner Insta lie tier; Proper s>ibc?rade preparation and c:o»i.=ii-.ruci-.ioii is crucial for a successful liner installation and would typically consist of subexcavation of compressible materials, sterilisation of July lS'S''. tho .'";:byr,-:^s.. r'T.ovs] or all roots, KI.tc:> •;, ntri.c? end ^* .-1. i -...,• ^^'.vi,.4/ *... t- '" - - — - • - -^ / t. ... Jt...i.^.^.J^.^.^l w4_ i#t^ sar:'": cv.::':iio,"i, jircr arid rcil csvsr, i"r.:. ^axli t"' i-i. of ..h-t liner ana fit'J.d ::e.:-,dnq Lik'juid be- c^rrioti out by approvt-o. int-.L^s Ilr:r£5 r.j! ical'/Url y iol T nv.'i nq l.'riv.r supplier instruc- tions. Soil cover is desirable but will require liner inclinations flatter than about 3 horizontal to 1 vertical. Liner Performance With the exception of polyurethane the base polymeric resins and asphalt show promise for long term resistance to the major ant\cipated constituents of uranium tailings. Caution should be ncted with regard to the following: - CPE nay bs affected by WROK sulphuric acid solutions - while not employed at Elliot Lake, kercv.ena is used for solvent extraction in scrr-.e milling operations and was sre-rrified for consideration in this study. Most of the liners will offer satisfactory resistanre to the low keror.ene concentrations antif j -• mO^t liiitir:; would L^_ adv::rG£iy ^ZZi.ci.cd by hich kerosene concentrations asE.ocicit.ed with accidental epillage. CojfiOd i: "• hi. 1 i fy ff'^.t- i ivj i-3i-r i'"'' <-,iv>" '"'V r>^,«-;rir> 7,:.^i-(-!.v/»-«:t-. Laboratories (FNt) on CSfS, FVC. HD?K ar>o Cstawfcic Airblow Asphalt in the presence of simulated acidic July 1'JSv v 841-3015 ur;i!ntiiii t J.i 3'. ;if.'s leaeha^.c WAS r<~-.v?. c... .-(i. Tl.-r ciata iri'li <;;:'_ t:5.; !:i-..;t, v.'Ll-h tnc •:':;••.'-''ptinn of PVC, <-!•<:.-• r..i i..;>• i.-:!.1; vere relative!/ uji.if Locccd by the 3 t_-ac.-M.?.t-- ' nr the short ten; periods. A review of published information acldrassincj t,ha effects of high levc-Js of garcna radiation on the physical properties of polymeric liners indicated that HDPE was least effected, followed closely by CSPE, EPDM, CPE and CR. PVC and Butyl showed the greatest reaction to gairuna radiation exposure. PNL estimates of the effect of gamma radiation on asphalt indicated that no physical defects were observed under the conditions of testing. Thin flexible membrane iJ.ners are susceptible to overstress- ing by stz-ains associated with larqe differential defornotions in the subgradc. It will therefore probably be necesotry to subexcavate and replace coroprassible materials encountered over the subgrade prior to liner installation. Similar concerns exist for liners placed on slopes and dam sections and wherr- there is a potential for excess hydrostatic or gas pressure buildup beneath the liner. Rates Scr>r>x.rji through liners is priivi-3rilv throuuh liner defects. A rational apprr-'-'Th to evaluating apparent cr field Itnec iti .:3 is ;.!.--.-u-;r. ictailr^ ™o:-:i r.^rj n-j of ov'.rtir.a 1 ior.s. ReviL-.-. o/ s-ich dr.t.3. ••;;;; in j tie.i.-?d diiriry tnir.