CRL Acrylic Radioactivity work September January 1991

Transcription

1 SA^T/C^/ 6 (C CRL Acrylic Rdioctivity work September Jnury 1991 Februry Abstrct This file contins summry of CRL work on crylic rdioctivity, three CRL monthly reports ( Oct 9 Nov 9 nd Jn *91), report on trce element nlysis in crylic nd drft on plnned crylic QC progrm 1 Summry Alph-spectrometry : A review of the crylic rdioctivity disequilibrium mesurements during the pst three yers hs been mde This technique is relible to better thn fctor of 2 In 6 out of 8 crylic smples the " Th to "Th rtio ws within 4% of unity for the Th chin The recovery of " R is not yet s relible but mesurements suggest no disequilibrium in the U chin TIMS : Vporistion nd mss spectrometry nlysis indicte Th levels between 5 nd 12 ppt for 8 out of 11 Polycst crylic smples (the others were t 16, 27 nd 32ppt), between 1 nd 4 ppt for 4 Polycst monomer

2 smples nd between 5 nd 11 ppt for ll but one Rohm crylic (7 smples, one ws mesured t 24 ppt) Six LANL spiked (t 134 ppb) smples were lso nlysed nd the men recovery ws found to be 88% +- 1% NAA : bout 1 ppt Th levels in 3g smples There is good evidence tht Polycst monomer is low in Th 7 out of 12 monomer smples contined Th levels of The Ge-counting system hs been upgrded to llow detection of or below 3 ppt, 4 others hve been mesured between 5 nd 8 ppt Previous evidence of n inhomogeneous Th distribution is confirmed by three new results on core (ll between 3 nd 5 ppt) compred to Th concentrtions of 9, 1, 16 nd 43 ppt on four surfce smples The pprent discrepncy between NAA results t Guelph nd CRL dt (mss spectrometry nd NAA) is being vigourously investigted by mny cross-check studies (stndrd verifictions, mesurements of spiked smples, intersite mesurements of the sme smples) The fctor of bout 3 between the two sets of dt is still not yet understood It is noted tht the discrepncy is between upper limits set by the Guelph group nd vlues mesured t CRL An evidence of correltion between trce element concentrtions nd Th levels in Polycst mteril (monomer, core, surfce, crylic) hs been found The correltion is strongest for Cr nd Fe Mny trce elements re lso inhomogenously distributed inside the crylic, the surfce lyer contining higher concentrtions thn those observed in the core Monomer smples contin only smll frction of the trce concentrtions mesured in crylic Alph-spectrometry, mss spectrometry nd neutron ctivtion nlysis t CRL give comptible results nd reinforce our confidence in their relibility The crylic QC progrm to be implemented during the crylic production will however rely principlly on mss spectrometry, minly becuse this technique provides results more efficiently All results on Th concentrtions in crylic obtined t CRL since September 199 with the three techniques vilble there re summrized on Figure 1 nd mesurements on spiked crylic re presented on Figure 2

3 Figure 1 Summry of Th mesurements in crylic Rohm Acrylic p? - Spect Monomer ClOEm] i3 u ^"3 P- Core Surfce on NAA Acrylic Polycst Acrylic 11 ll I l Q Polycst Monomer Rohm Acrylic O O TIMS Rohm Core Rohm Surfce 1 nnt Thr\rii im

4 "l^^^»"!t Figure 2 Results on spiked crylic - Spect NAA OC TIMS 1 A 15»^»-\t-\»»^ jil 2

5 Acrylic Rdioctivity Report Edited by Erle, Nov 1, 199 Summry: At Guelph, mesurements hve been mde on number of rope smples nd on the Polycst "cndle" mteril (smples tken from the core of the sheets) At LANL, crylic smples spiked with 232Th hve been mde They hve confirmed their high recovery efficiencies nd precise Th determintion by NAA Spiked smples hve been distributed to CRL nd eventully to Guelph (vi CRL) for verifiction of their procedures At CRL, the confidence in the relibility of the TIMS results continues to be high nd our confidence in the NAA results hs much improved during the lst period There is now good evidence tht the Polycst monomer nd crylic sheet cores re low in Th (3 ppt) The high vlues observed in mny smples over the yers my be due to Th concentrted on or ner the surfces of the sheets The Th in the kevlr rope is higher thn we would like it to be if it is to be used to support the vessel

6 c LANL Acrylic Report (Edited by Erle from bitnets received) Abstrct: Smples of crylic spiked with Th hve been mde for distribution to the collbortion for checks on their mesuing techniques The uniformity of the spike nd the mesuring techniques t LANL hve been verified Text: We (Jerry t LANL) hve ssyed by NAA Th spiked crylic mde t LANL by Mc We took four different smples from the first rod Mc cst Ech smple ws bout 35 gm The totl rod weighed 3355 gm nd Mc dded 46 microgrms of 232Th (ie 134 ng/gm) After irrditing for one hour we counted the 233P to determine the 232Th concentrtion We used our well counter nd counted ech smple in one direction nd then rotted it 18 degrees nd counted it the other wy (this checks for nonuniformity of the Th distributions - with previous commercil sources of crylic we would often see detection rtes vry by substntil mount when this rottion ws performed - thus indicting non homogenities in the smple) The results were: smple irrd port orient 1 orient 2 31 R / / R R R As you cn see ll of the smples gve good greement with the dditive mount nd showed no significnt inhomogenities The smple 33 ws irrdited in different port thn the other three nd gve somewht low vlue We did not hve specific flux monitor in the irrdition With previous flux tests we hd reproduced the rectors climed fluence (97el2 n/cm2-sec) in both ports nd therefore do not regulrily check the vlue The rector hd been shut down for long mintinence perior nd we hve not used it recently However, one of my collegues clims tht his smples done in the R-5 port wereconsistenly giving 5% lower vlue thn the other port If we would scle the 33 smple up by this 5% fctor then it would b& in excellent greement with the others The bottom line is tht we re quite confident we hve very well clibrted smple contining 134 ng/gm of 232Th

7 One of these irrdited smples hs been shipped to CRL where it will be counted with their well shped Ge detector Mc hs mde nother crylic rod spiked with Th nd tht lso hs been shipped to CRL together with smll portion of the first rod, portion tht hd not been irrdited CRL plns to count the s til irrdited piece immeditely upon rrivl nd do NAA nd vporiztion followed by TIMS nd lph counting) on the unirrdited smples Smpes should lso be sent to Guelph One other item of informtion We took one of our irrdited smples (#31) nd dded some 231 P trcer (s we hve done in ll of our previous mesurements of commercil crylic) nd then voltilized the mixture using our stndrd technique We did this s method of certifying tht the spike behved in the sme mnner s the bulk crylic The results were: 233P from crylic = 86 +/- 6% recovery 231 P from spike = 841 +/- 18% recovery This is very grtifying in tht it shows (s we hve lwys ssumed) tht the trcer behves the sme s the bulk mteril

8 CRL Monthly Report on Acrylic Rdioctivity Bonvin, Erle, el, Hurteu, Mrtin, Millr, & Milton ) Alph Spectrometry Section: (contct Milton) Since the CRL Sept meeting 8 kg of Rohm mteril hve been vporized nd seprtion of the Th U nd R isotopes re bout to begin It ws noted tht the R spectrum from one of the smples reported t the Sept meeting contined 224R pek indicting concentrtions of this short lived isotope much higher thn would hve been expected from the 228Th concentrtion mesured in the Th spectrum This could not be due to disequilibrium but must be from 232U contmintion 232U is used in the lbortory s trcer nd it must hve gotten into the R strem but not the Th strem The conclusions of the report tbled t the Sept meeting re unchnged b) Vporiztion nd TIMS Section: (contct Erle) i) Kevlr Rope - 38 ppt Th A 58 g smple of kevlr rope ws vporized nd nlysed by mss spectroscopy ue to the lrge quntities of other solids in the smple the solution following the vporiztion ws pssed through n nion exchnge column to isolte the Th nd U The level of Th nd U ws found to be 38 ppt nd 21 ppt respectively nd is consistent with NAA mesurements t Guelph ii) Guelph Shop Acrylic ppt Th A 4 g smple of shop crylic mesured t Guelph by NAA to contin less thn 2 ppt Th (see SN6 in the report t the CRL Sept meeting) ws vporized nd mesured by TIMS to contin 11,6 ppt Th Recently Guelph hs found tht with better sttistics these 68% confidence limit numbers my be misleding Smples initilly considered to be less thn 2 ppt re in fct more like 5 ppt In ddition, the yield from their Al stndrd ppers to depend on its loction with respect to the crylic (See the Guelph section of this report) Cross checking of smples will continue iii) Polycst "cndle" , ppt Th Four smples of Polycst crylic tken from the "cndle" distributed by Peter oe hve been mesured nd shown to contin 1, 16, 27 nd 32 ppt Th In ll cses the U level ws bout 25% of this concentrtion These Th levels re significntly higher thn the 5 ppt Th reported by Guelph from n djcent piece of the sme sheet

9 /-> iv) Rohm for lph counting - 48 ppt Th A quntity of Rohm mteril hs been vporized for disequilibrium mesurements The 232Th concentrtion by TIMS is 48 ppt v) Polycst Monomer , nd 28 ppt Th Quntities of inhibited liquid Polycst monomer (round 8 litre) hve been evported nd the Th nd U in the residue mesured by TIMS The levels of Th my depend on the plnt loction of the smple Smples tken from the delivery truck (28 ppt Th) the underground storge tnk (36 ppt) nd the mixing vt (15 & 13 ppt) hve been mesured c) Neutron Activtion Section (contct Bonvin) Results: Rector opertions t CRL relese few times week high levels of Ar-41 nd therefore drmticlly lter the sensitivity of the Ge-well detector mesuring neutron ctivted crylic smples A stndrd mbint rdition monitor hs been instlled nd is being used to utomticlly stop dt collection when Ar-41 is detected Accordingly the bckground in the 312 KeV region hs been reduced to 12 counts/hour/kev t on Polycst mteril (12 smples), irrdited during September 199 re presented in Tble 1 For comprison mss spec results on Polycst mteril (described in nother section of this report) re lso presented The monomer smples for NAA were uninhibited 3g smples tken from vrious loctions in the Polycst plnt The crylic smples were from the lrge sheet of Polycst "cndle" mteril distributed by Peter oe nd mesured by the GST (Guelph Sno Tem) to hve 5 ppt The core nd the surfce smples were from erlier Polycst mteril on hnd t CRL nd were prepred by lser cutting t NRC NAA ppt Thppt Th momoner (truck) 19 (8)63 (12) monomer (tnk) 24 (8)38 (4) monomer (mix-room) 3 (1)19 (8) crylic, "cndle" 2 (8)23 (6) core 46 (13)34 (11) surfce 16 (3)1 (4) Mss Spec ppt Th , 13 32, 27, 16 1 Tble 1 Th levels (stt error) in Polycst smples mesured by NAA or Mss Spec

10 L- These NAA results re preliminry since we re still studying the relibility of the Th monitors used during the irrditions (cf "the Guelph depletion effect" ) nd we would like to get better confidence in the fitting routines used to determine the net pek re Observtions: 1 The sensitivity of NAA is now round 1 ppt thnks to the lower bckground 2 Four out of six monomer smples show low Th level (2-3 ppt) The higher vlues for the two other smples my be due to externl contmintion 3 Th levels in core crylic nd in monomer re similr 4 The levels of Th in the surfce nd core components of the crylic re different in greement with previous evidence (see September 9 report) of n inhomogeneous distribution of Th 5 Th mesurements by NAA nd by Mss Spec give comptible results iscussion: 1 The good greement between Mss Spec nd NAA dt s well s recent results from Los Almos on spiked crylic (high recovery efficiency fter vporistion nd precise Th determintion by NAA) reinforce our confidence tht both methods re dequte to determine ppt levels of Th in crylic smples 2 The following scenrio my describe the observed Th levels in Polycst crylic: * The monomer nd the core of crylic smples hve 2-4 ppt of Th * Rndom contmintion during either the mnufcturing of crylic nd/or the hndling prior to mesurements contribute (in mjor wy) to the higher Th concentrtions observed in crylic This contmintion is rndomly distributed on or ner the surfce

11 CRL Acrylic Rdioctivity Report for Nov Summrized by Erle Abstrct: Levels of Th in the severl rope smples checked re higher thn we would like for vessel support New mesurements on the monomer increse our confidence tht clen crylic rw mterils cn be obtined for SNO Intersite comprisons of results suggest inconsistencies which hve not been resolved ) Spiked smples from LANL hve been vporized nd the Th content mesured by TIMS LANL clims tht the spike ws 134 ppt nd they mesured ppt by NAA We hve mesured 14 & 112 ppt (suggesting bout 8% recovery) We pln to increse the dt set b) Lst month we reported tht the vporiztion nd TIMS gve 38 ppt Th for kevlr rope (cf from Guelph) We hve now mesured 88 ppt for the spectr rope (cf from Guelph) We must try to get better rope c) The dt set on NAA on monomer hs been incresed Three more smples hve been mesured for Th Truck <15 ppt, UG tnk 3+-7 ppt nd mixing room ppt The mixing room smple lso showed significnt levels of Cr, Zn nd Fe d) Irrdited crylic from Guelph, shped s 4 g Mrinelli bekers, hve been vporized nd the residue both gmm counted (two smples) nd TIMS (four smples) Guelph I Guelph Th CRL Th CRL Th CRL U ppt (gmms) gmms mss spec mss spec J3 pprox J4 " Jll < J < This mteril is the Polycst cndle which lst month ws reported by CRL to be round 2 ppt by both NAA nd TIMS The surfce to volume rtio is probbly lower for the Mrinelli bekers thn for the CRL mteril which might explin the 2 ppt s compred to 5 ppt The differences between the TIMS nd NAA numbers re disconcerting The NAA vlues depend on the correctness of the Al monitor (the monitor is required for both the Guelph nd CRL gmm results) which is being exmined t Guelph nd t CRL

12 CRL Acrylic Rdioctivity Report Feb 1, 1991 Alph Spectroscopy A review of the crylic rdioctivity disequilibrium mesurements during the pst three yers hs been mde Over this period of time bout dozen mesurements hve been mde on crylic from vrious sources nd the following conclusions cn be mde ) The technique for checking the Th chin compres the 232Th to 228Th rtio nd this technique is relible to better thn fctor of 2 In 6 out of 8 exmples the rtio ws within 2% of unity, in the other two it ws 4 nd 17 but the levels of Th were low in both these cses Also in ll eight cses the vlue for 232Th for portion of the residue s mesured by mss Spectroscopy greed with the lph Spectroscopy vlues to better thn 5% giving confidence to the bsolute relibility of both techniques for Th b) The sme confidence hs not been obtined for the U chin In this chin we hve compred the 238U to 23Th concentrtions nd lso the 238U to 226R concentrtions From SNO point of view the 226R vlue is the importnt one nd relible recovery efficiencies hve not yet been obtined for this element The 238U/23Th rtio is less interesting nd for 7 exmples this rtio is less thn unity six times (typiclly it is bout 5 but in one cse it ws 2) In the five cses where 226R ws recovered nd mesured no evidence of disequilibrium to within fctor^of^two^ws reported but we must cution tht there re lrge uncertinties in the recovery efficiencies ssumed A comprison of the 236U concentrtions with those mesured by mss Spectroscopy for the sme residue gree to within fctor of two for eight cses This is poorer greement thn for the Th comprison but dequte c) At this point we recommend tht the qulity control progrm for crylic concentrte on mesuring the Th disequilibrium nd not worry bout disequilibrium in the U chin This recommendtion is mde becuse the U concentrtions re lwys lower thn the Th nd the importnce of U s compred to Th is 1/4 s fr s SNO bckgrounds re concerned Only if we cn ttin significntly more confidence in the R recovery techniques for trce quntities of this element should this recommendtion be reconsidered Mss Spectroscopy Vporiztion followed by mss Spectroscopy hs been selected s the min method for checking for Th nd U in crylic nd mesurements on crylic nd rope hs continued t CRL ) Four more pieces of crylic spiked with 134 ppt Th t LANL hve been mesured, in ddition to the two reported previously The six vlues obtined re 112, 14, 126, 126, 119, & 57 ppt We hve no explntion for the low vlue of 57 ppt The two t 126 ppt were slow burns s distinct from our usul rte of vporiztion It would pper tht we re losing bout 1% of the Th during the vporiztion nd n dditionl 5% during the smple preprtion for mss Spectroscopy You my recll tht in My &9 we reported on recoveries for Th nd U from crylic spiked with nitric cid contining Th nd U t CRL The recoveries fter vporiztion nd mss spect t tht time were % for three smples We cn conclude tht our Th recovery by this method is bout t for Th in crylic b) Mss Spectroscopy of Rohm mteril compring surfce vs core of the sme sheet my be inconclusive The opticl surfces removed with bnd sw contined 137 ppt wheres the core ws mesured to contin 73, 45,

13 , nd 216 ppt (verge 75 ppt, obtined by dding weights) This is progrm should be continued c) Other mesurements on miscellneous crylic smples - Rohm cndi 11-6, 6, 5 ppt Th Rohm piece shipped fter Aug visit - 91 ppt 11 n r» ii ppt Polycst piece shipped with nonomer - 1, 12 ppt Stnley monomer contining c her junk - 13 ppt Spectr rope - 481, 88 ppt d) Smples irrdited nd counted t Guelph hve been shipped to CRL for mesurements The results re reported with the NAA results in the next section Neutron Activtion Anlysis ) New smples of Polycst- mteril hve been neutron ctivted nd counted The following results gree with mesurements previously reported : Polycst monomer (truck) monomer (truck) monomer (tnk) monomer (tnk) monomer (mix-room) Polycst core (lser cut) sides ( " ) opticl sides (") ppt Th (< 15 ppt in Nov) < 16 ppt Th ppt Th ppt Th ppt Th ppt Th ppt Th ppt Th b) Mteril from other suppliers ( 4 crylic smples from Rohm, 1 crylic smple from Stnley, 1 smple of crylic dditives from Sweedlow ) hve lso been irrdited However since they ll contin significnt mount of phosphorous, the pure bet emitter P-32 (hlf-life of 143 dys, Q-vlue of 17 MeV) is lso detected ty the Ge-counter nd lowers the Th sensitivity to ppb levels NAA is therefore not suitble to nlyse smples from those suppliers An lterntive would be chemicl seprtion of the irrdited smples but this procedure, s we hve experienced, my introduce other uncertinties c) Two LANL spiked (Th concentrtion 134 ppb) crylic smples hve lso been nlysed: LANL smple 1 : ppb Th LANL smple 2 : ppb Th,, The second result is puzzling but n exmintion of the tiny qurtz tube contining the monitor during the irrdition showed it to be improperly seled d» The consistency of 45 monitors used for NAA during the lst 6 months ws nlysed nd n indiction of creless monitor preprtion detected The dispersion in counting rtes observed between these 45 monitors ws 28%, which is uncceptble lrge -The neutron ctivtion t CRL is lwys performed t the sme loction in the rector nd therefore neutron flux proportionl to rector power cn be ssumed Normlizing the monitor counting rtes to the rector power during the irrdition did not chnge the observed dispersion Even monitors irrdited in the sme continer presented similr dispersion We therefore believe tht the problem ws ocurring during the monitor preprtion

14 " Since this nlysis ten monitors hve been prepred with greter cre nd irrdited simultneously The dispersion observed fter Ge-counting these ten monitors ws only 5% e) 4 kg smples irrdited nd counted t Guelph hve been shipped to CRL for counting, for NAA nd for mss spectroscopy Some of these results hve been reported previously nd indicte Guelph/CRL discrepncy A recent summry of results from Guelph re different from erlier reported informtion (see Nov report) but the discrepncy is confirmed A complete tble of results re s follows in ppt of Th nd includes informtion reported in Nov Smple Guelph CRL CRL CRL v I NAA 4kg Vp 4kg NAA 3g Vp 4kg gmm gmm Mss Spect j3 < ^ 78 j4 < (lter) jll < jl <6 53 jl4 <26 <7 62 J15 <18 jl6 <32 <4 116 Col 1 is the smple identifiction Col 2 is from gmm counting the P fter neutron ctivtion t Guelph (note two mesurements for J4) Col 3 is gmm counting the P fter the smple ws shipped to CRL from Guelph, vporized t CRL nd the residue collected for mss spectroscopy Col 4 is for NAA of smll portion of the 4 kg when the reminder wg vporized for mss spect Col 5 is from mss spect for ll or most of the smple Comments: i) The lrge vlue of 116 ppt for Jl6 is from contmintion introduced during rinsing t CRL nd is understood ii) The gmm ry bckgrounds during counting of the vporized smple Jll t CRL where four times those of Jl2 Yet Guelph ws ble to put their best limit on Jll wheres Jl2 ws their worse smple A mix up in lbeling might expnd this discrepncy iii) The CRL gmm counting of smples irrdited t Guelph is consistent with the Guelph gmm counting The NAA nd gmm counting t CRL is consistent with the mss spect t CRL The reported Th in identicl smples is consistently higher t CRL thn t Guelph by bout fctor of 3

15 Correltion between trce element concentrtions nd Th levels in Polycst mterils E Bonvin Februry The trce elements of twenty three 25gr smples of Polycst mterils (12 monomer, 3 core crylic, 4 surfce crylic nd 4 crylic) hve been nlysed An evidence of correltion between the concentrtions of some of these elements nd the Th concentrtion hs been found The observed count rtes (per unit weight, corrected for decy to the irrdition dy) of neutron ctivted isotopes of nine trce elements (^Ce, ^Hg, "Cr, ^Au, ^Sb, ^Sc, "Fe, "Zn nd "Co) re presented in Tble 1 together with the mesured Th concentrtions Since this nlysis hs been initited fter the smple irrditions, no effort hs been mde to present the dt in bsolute concentrtions This step would hve required simultneous irrdition of known stndrds for ech of the elements The normlised count rtes presented here re simply proportionl to the bsolute concentrtions since the irrdition conditions ( 6 hours irrdition t the sme position in the NRU rector with monitored rector power stble to within 5% during the irrdition time ) were similr However smll (bout 3g) Shop crylic smples hve been reported by the Guelph group t the Chlk River collbortion meeting in September 9 to hve concentrtions of bout 5ppm for Fe, Olppm for Zn, 2ppb for Cr, Ippb for Co nd 3ppt for Sb

16 The verge of the Th levels in those smples ws bout 35ppt No evidence of correltion between the Th levels nd the levels of other elements ws observed by the Guelph group The normlised count rtes of neutron ctivted isotopes of specific trces re shown in Figures 1 to 9 s function of the Th levels mesured in the smples A correltion is clerly evident for some trce elements (ie " Cr with correltion fctor r=83 nd "Fe with r=58), while lmost nonexistent for some others (eg^hg with r=23) Core nd surfce crylic smples exhibit quite different count rtes for some of the n-ctivted trce isotopes nlysed, confirming the evidence of n inhomogeneous distribution of impurities (nd lso of Th) in the crylic ppers tht ll Focussing on the monomer dt set (12 smples), it smples with Th levels bove 3 ppt contin much lrger concentrtions of especilly Cr (nd lso Fe nd Zn), which my be understood s leching contmintion for SS continers (delivery trucks, piping, etc) since Cr is known to migrte to the SS surfce However the Th nd the other trce elements levels observed in monomer re smll frction of the concentrtions observed in finished crylic, therefore priority should be given to identifying reducing) the contmintions occuringfter the nd voiding (or t lest mix-room The observed correltions between Th nd trce element concentrtions my be used either to identified the sources of Th contmintion (s mentionned in the cse of the monomer smples) nd/or to select low Th mterils on the bsis of their trce concentrtions For exmple, requirement of "Cr count rte not exceeding 5 counts/dy-gr (represented by n rrow on Fig 3) would select ll but one smples with Th level below 5 ppt nd reject ll smples bove tht concentrtion Other trce elements (like Fe, usully present t bout 5ppm in crylic) my lso be suitble for similr selection procedures

17 smple I Th (ppt) Cel41 Hg23 Cr51 Aul98 Sbl22 Sc46 Fe59 Zn65 Co6 Count rte (Counts per dy nd per gr of smple) Monomer: <! " Core crylic: Surfce crylic: Acrylic: Tble 1

18 , i il,j r -- V : <! CT «>, CO ^co ^~1 I? 6 o o - Fig 1 CT «> S2 CO ^CO - : Hg-23 Fig 2 o t ; Ce Qot Thorium i i,,,,,,,,,, 81 1 Qot Thcirium «-=c fcj OS g1" >^ CO o L; C3> ^ c >^ CO 5 w ^CO B o Cr-51 B o Fig 4 C Fig ,,,,,, oot Thorium t 1-81, Au-198 i ^^1 1 ot Thorium

19 * - - o o o ^ ( & «>< CO ^en *^ i B UB : Sb-122 L; 5 < >» r- 3 5 ( ^3 - ; o o Sc"46 o O - o o Fig 6 ^ Fig oot Thorium,,,,,,,,, ^ 81 1 t Thorium n Fig 7 $2 ^g 8 * ) «>» ( P ^^ C 3? I ^ CP : Fe-59 Q o, f 1 1 1, 1 1 I " oot Thorium ot Thorium ij ) «>» CO ^s Ċ3 ^,, " : B Q Zn-65,, o,,,,,,,,, o,,,,

20 Q Co not Thorium

21 1 /- ] Acrylic Vessel Qulity Control 1st rft by Erle Vlentine s y 1991 Introduction: There will be mny steps in this procedure This note is only ment to ct s begining in defining wht will be required QC will be required on the rw mterils ie the sheets, bonding gents nd cstble components nd on spects of the finished vessel Rw Mterils: QC of the sheets ws discussed t length during the 1989 visit to Polycst, one of the potentil suppliers of sheet mteril nd ws documented t tht time Excerpts from tht report follow: Reynolds will need 16 7"x<5 JcS sheets, 45 3ffx4fx8f sheets nd 37 2f x4 x8t sheets Polycst hs 29 mchines ech of which cn mke up to 28 sheets of 1" mteril t time nd ech cn be configered to mke number of sheets of vrious thicknesses A possible running scenrio might be to use four mchines t time, 2 mking 25 7" sheets ech, 1 mking 12 3" sheets nd 1 mking 12 2" sheets This scenrio would be repeted up to four times to get the entire job done nd would tke bout 6 weeks They mke bout 3 t of crylic, or the SNO vessel, dy Roger would like to hve for ech sheet, the btch, sheet nd monomer lot numbers The spectrl scn, the tolerences in thicknesses nd the results of visul inspection All this Polycst routinely provides to customers tht sk for it We would hve to do the Th nd U checks nd ny other confirmtion checks tht we wnted to do on their mesurements We will hve to determine the specifictions tht we need Roger ws concerned bout the thickness uncertinties which seem to be bout 7% Once we hve routine for checking for Th nd U set up, Lee will supply us with 1 litre of the monomer from the truck, I litre from the underground tnk, 4-1 kg pieces from 1 sheet nd 4-1 kg pieces from four other sheets ll from the sme btch nd we will do this three times Le will do the light trnsmission on the 24 pieces nd CRNL will do the Th nd U mesurements

22 -7- If the tests proposed in the previous prgrph show btch consistency then we will check the production runs the sme wy Since we will not be ble to keep up with the production (Polycst cn mke ll our sheets in two months) we will probbly hve to mke our mteril in two one month periods The mount of mteril ordered in the second production run will depend on the success of the first production run If the firm cn use the rejected mteril in some other ppliction we my be ble to get rebte since I doubt tht they will be prepred to qurrente the Th levels to our stisfction The firm will do their usul QC, including opticl trnsmission mesurements We will cross check the opticl QC in some cses only The Th nd U checks will be s described bove for ech btch or more detiled thn tht if necessry The Th nd U will be mesured, by mss spectroscopy t CRL where bout five smples per week could be processed (ouble tht rte if it ws required) Tests on the strength of the mteril will hve been performed prior to ordering nd it my be ssumed tht the sheet mteril will hve dequte strength Similr rdioctivity checks will hve to be done on the bonding mterils chosen by the vessel fbrictor nd on seprte test smples mde from time to time by the fbrictor Bonded Vessel: Test smples of the bond joints mde during vessel ssembly will hve to be checked for Th nd U in similr wy to the sheet tests nd, in ddition, the smples will hve to be mechniclly tested (see Peter oe for this section) Opticl checks on the bonded joints of test smples nd the vessel cn be visul There will lso hve to be series of cceptnce tests performed on the completed vessel (Add text here, if possible) Smples will lso be mde during erection nd left in the wter for future geing checks This progrm must lso be detiled