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CHBI*71T--»AaAnON KOCtUtl PCR K.IHOKIUM AND URANIUM
106 ALAN08 SCIEXTITIC LASORATOT
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THE DECONTANDIATICN Of URAEXUH FRCP PISSXCM PRODUCTS BT THE USB OP THE URAHIL OXAUTI PRECIPITATION REACTION
Report written byi
DATE APR 12 1957 6. L. Ktlcnner For The Atomic Energy Commiteion mTi A Q a m AJUL Chief. DoelattifiCAtlon Branch
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ABSTRACT
Decontamination factor* of the order of 10 vert obtain** for R « m and r toitura preecnt at flit loo product* vfata urtnlua vat precipi
tated fro* 90 a C activity level *olutloae at uraayl oxalate undtr
noraal urtniua yield condition* for three cycltt ( r & i ) • Factor* of tha order of 10^ vtrt obtained by the uat of this
reaction vlth tladlar tolutloot undtr relatively high urtniua jrlald 0 condition* for thro* eyelet (~9<#).
The urtniua parotid* precipitation reaction proved to ba of no m value on auch aolutiooe, yielding decontamination factor* of only
17.1 for 9 emitter* and 1.2 for r emitter* for three cycle*.
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Reference*; P. A. Bo. CMH-B-b (5RP#0)| LA RoUbook 2957.
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Is COO&SOtlaO with tte RaU prog?** i t this laboratory, it VUI . proposed that 5 k4 of enriched uranium 1m subetttuted for the two
ton* of l o m l uranium no* I m d U M 1a tte Sanford File to product ik n tte required quantity of active | | “ ;- This would relieve the prob-
1m of storing large volume* of highly active normal uranium eolu- I k A tlQBt after the fit ted t e a removed. However, tte monetary volte of enriched uranlua would necessitate ltd recovery and Aecontaains- IkA tion to that it could te recycled te a m r additional la wai rt- qutred. / /^lailtetU a of tte quantity o fte 1*0 needed for single ejq>eri**nta
raaga up to 10,000 c, which would mod initial actititle* of tte ir radiated uranium on tte order of 10^C. Decontamination factor# (after m oral of tte Ba^°), therefore, should approach this value so that tte enriched uranium could be re-cycled through standard procesaea to flniated astal shapes with a Minima of ahislding of the opmtlooa Involved. Although auccesaful decontamination of uranluai from flesion pro ducts tea been achieved through the use of solvent exttmetion pro cesses, i t wae further proposed that precipitation reactions be in vestigated as to tb sir ab ility to dscoataaioate uranium under these conditions. Certain process advantages are obvious for preclplta-
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tlon*type reactions. The urmniua pere&tde reaction (30* 8«0» M precipitant) and tha urmnyl onalabs reaction (fl*C* II - Experimental Consideration* ymWm 1. nature of activity at th* tla* of attested decontamination, It wee assumed at the outset of the problem that a cooling period would bo allowed prior to attempted decontamination. This 11would gs decrease . - the ^ in itial ’ activity by perhaps half and leave coat esdiua-llved, but chiefly long-lived, isotopes. This cooling period paww cr a t-fT T 'S f**b, vould here to be At such etmmug level u to permit direct handling of the aateriel within certain Use Unit*, end with the use of •lapis tooge. pel culat Iona. Thi* work vt» carried out on normal tumulus solutions to vhlch •m il quantities of ft to loo product activity warn added. Since nor- aal uranlua (eepectally old preparations) also contain* 0 and r actl- rity from certain laotopee la the natural decay chain, this radiation sat subtracted, froa the fla*Ion product activity. To obtain thtM blank valuta, "hot" experiments were duplicated by "cold" experl - aenta — actually preceded by them, thus also providing technique experience, especially in the use of tongs, remote vacuus transfers, etc. Solution allquota were counted before a precipitation vaa made. Then, a fte r the cake vaa washed, converted to an oxide, re-dissolved, wad amde up to a definite volume, solution allquota vara again counted. This value be cam the starting count for the next preclpl- tatlon, etc. In this manner, any value divided by i t s succeeding 1 value provided the decontamination factor for that precipitation; or, the Initial value divided by the final value of a series of precipi tation* would equal the total decontamination factor obtained for ■ W i mm i « |SiEi^^®';: w fiMPU Calculation*. The following calculation*, shovn in Table 1, war# fcyn l— t D-2, and are typical of the calculation* and* for all the m experlaeatal work, with the except ion of soae of the early experi- p%; mot* where no r activity determination* ware aad*. TABLE 1 8 Decontamination Result* Result, Total Corrected (naan) Activity, Total Acti c/a c/a v ity . c/a SECRET r Decontamination Results Sample Dtcco- Result, Total Corrected taain- Total Acti atlon Sais. Aliquot c/a vity. e/a factor starting soln., "hot" 1/2500 Too 1.75 * 10S 1.73 x 10*' starting sola., "cold" 1/8500 8 —2.00 x 10H J f i r s t ppt., "hot" 1/2500 39 9.75 * 1 0 S M 3 * 10 f i r s t pipt., "cold" 1/2500 20 5.00 X 10* 1 b.O second ppt., "hot" 8/5000 19 1.19 X lo S second ppt., "cold14 8/5000 53 5-32 X 10k j k.e th ird ppt., "hot" 8/5000 6 3.75 x io5'j 2.50 * iO5 third ppt., "cold” 8/5000 2 1.25 X 105 ) Total V - 692 •Average total 9 activity found for 30 gas. noxml U w i 2 x 10* c/a. **Awragi total r activity found for 50 gaa. normal u tat 2.5 a 10* c/a. eeesinca the blank value It higher than the hot value, It miMt be neglected. 3 and r counting of the sample# eat done by the RaLa chemistry group (CHR-10) • Counting results were corrected fo r background and coincidence before being reported to this group, lo further correc- •« ... . • • n »• . ... ** • 1 • i.» »»» . • • ♦ • » ... » » ... 1 • :• 1: ::: 1.: w.... 5 «• ::■ • «• rnmmmmmm l&SMffigmi mm ' rnmmmsmSim^mrni 1Hi tioas w n applied to the calculations other thau the subtraction of blank Talt*». Decay of the activity over the experimental period was awai t, enough to be neglected. (8ee "Sources of Activity".) A swell fraction of the decontamination la attributable to uranlua yield it self — e.g., if a decontamination factor of b were obtained after a precipitation vhoea uranlua yield vat $OJt, then only half that decon tamination would be due to cheaioal purification. This is a severe •xasQle, however, and on the basis of uranlua yields and accoepaaylng decontamination factors given later In this report, yield effect* were negligible and no corrections vere wads for them. Sample Preparation. Aliquots were so arranged that one al of solution contained enough activity for a reasonably accurate beta count. This voluas of (solution vas evaporated in a glass cup 7/8" X.D. and l/b" deep. Duplicate sasplea were prepared and the cups placed in the counting chamber. The wean, corrected result was used in the calculation# as noted. 10 al solution aliquots vers given directly to Group CXR-10 for counting. This group carried out the sample preparation for these aliquots using annular type counting bottles. PPPP'P; Sources of Activity. :.r. - •Vv;7^v. • ;p3':: P;, & ^ Two sources of fiesion products were used to supply the 0 and r activity for the experiments: SECRET I". •** •’« » •" •** » •** • •'* »*• * * •• » ...... »>• ... < . ut.. . i • S «•.. .. •• p i ■ 1. Uraayl nttraU •olutloo froa the Um AUk * eater boiler, th is •olutloo conUlo*4 k$Q o§. of uranlua (tt.9> V~S$5) per ml. Staples received after 3 w athe' decay emitted approximately 1*6 ■C o f r activity par ml, Manured by •array Mter*, aad at 7 mantle, 0.7 mC of r activity par ml, meaaured la the m m my. A maple taken for 0 count at tha beginning of the eaparimante ahoeed the following decay with respect to time: Dag e/». » 0 9 W b 9067 3 9 »5 6 9«rr> 7 90*8 10 88X0 TbcM data arc plotted in figure i. 2. Urmnyl nitrate tolutloo from the dl■•olutloo of a Chalk River Pile slug. Pour 30 aC eaaplaa vert received a fte r about ) months' da* cay, containing the following velghte of U and Pu per aaqplat total U • 2.65 am. U-255 . 0.016 e u . * 3 8 3 1 3 SP 1 r: - im tn w n rn v f ;^v-r<:^ JH H . Staples token for 0 H i r count ibovtd the following decay nth respect to tiJWt s/bjl c/SlX o 37*3 57,200 k 3723 - - - - - 6 53,ooo 7 3633 U 3317 ISfi The os date ir« plotted la Figure l i t - Kxperlnents m A. Decontamination by the Use of the Uranium Peroxide Ejection at Various Ac liltle y . Two 500 «1, 0.42 M uronjrl nitrate solutions were Bade froa the dissolution of tfeOS in nitric told. To one was added s aC of water boiler solution before the final volume adjustment was nsde. Aliquots were tbsn taken from each solution for p counting. A uranium peroxide precipitation was aade on each solution bp the simultaneous addition of a 30)1 excess of 30)1 BtOe end 1:1 anaonlun hydroxide at a constant pH of 2*3. After a 5 minute digestion period and a short ssttllng period, tbs slurry was filtered through a fine, fritte d glass Bdchner funnel n t h a nlnlim of washing. The funnel was placed in a soul crucible furnace and the U04 converted to U0» - 11- SECHET * ... •• j j r* j. {/.: • : i \ \ \* : : «•Hi ... Is • I .M |*l : ::: •:: •««.« :: WV«a»--= ______Sm t * ■ % i a t )00 C for several hour*. Thla oxide vat dissolved In n itric acid, aads up to 500 al volume again, and aliquot ted for re-counting for the 3 activity. The experiment vat repeated a t pH 5.5 *&d 1.5 on "hot" solutions only, using tbs final solution from tbs pH 3*5 experiment as the starting solution of tbs pH 1.5 experiment. jMM tor pH 1.0, the same scheme vas used again, this time lncludirg the "cold" precipitation to provide a blank value for correction of the "hot" result. Decontamination results are given In Cable 2. Although uranium plaids are not given, the reaction Is essentially quantitative In this pH range. TABU 2 ,tlon Achieved by the Uranium Peroxide Reaction at Various Acidities : ijj §1 , \ Decontami Total 0 Activity In Total 0 Activity nation Starting Soln.. c/a After 1 Fptn., e/m factor £ L 1 5*5 6.28 X 107 5*18 * 107 1.2 2.5 b.51 x 107 (corrected) 2.12 x 107 (corrected) 2.1 1.5 5.18 * 107 l .U x 107 4.7 1.0 13.2 x 107 (corrected) 1.50 x 107 (corrected) 10.1 Decontamination factors are plotted against pH in figure 3« DETTi-i 5 5 I H !:.!) vf. — v» »—»— — *•""'* .* ' •’ I—'-” 1 ■ "■"**' ' - --v ' ».$£*• V «••<• . • ' j M m■ ilia® mi. m i i l ? SECKST . m "W£M m 1 m m B. PrtolplUtlott on Pieontonla»tli». 1. The 500 al solution remaining from the "hot" precipitation at pH 1.5 ( m s Exp. A), containing l.U x 10^ c/m 3, total, was nad* nor 'm mal vitn rsspset to frss HXQs and hasted to etsan bath temperature. The uranium waa precipitated as uranyl oxalate by the addition of 150 . I ^ ml o f h o t, aqueou* o x a lic ac id so lu tio n (co n tain in g 29 gas. HaCsO^BHaO) The slurry was stirred for about l l / 2 hours until it had reached room temperature. The precipitate was filtered out, transferred to a plati num crucible, and Ignited overnight at 800°C. This oxide was dis solved In nitric sell, nade up to 500 al toluaa, and aliquotted for 0 5 §s» counting. The result was a total count of 8.75 x 10 . This la a decontaalnatlon factor of approximately 13* ■lit?wmm By obtaining the weight of the crucible before the tfeOa v u die- solved, the uranium yield was found to be 90)1 for this precipitation. 2. The 500 al solutions remaining from both the "hot" and "cold* precipitations at pH 1.0 (see Ixp. K) vers precipitated as uranyl oxa late aa above. The corrected starting count was 1.30 x lo7 c/m 3; the corrected final count was 7.0 x 10^ e/a 3, giving a decontamination factor of 19* Again the uranium yield for the precipitations eat about 90Jt. |gg|g W IB i t o f Bold'-Bacl on Decontamination. m mm Two aspects of this technique vers investigated. In the first experiment Al, Mg, and Fe were added to determine whether they would -15- . * n m SBC RES e#; M* e *. * ...... •• tv* • 1 ... • • •«• . t ♦* ••« 1 • •• it • •t •... a ...... *» ...... »• i ... •».* BB m m IP w . mmm i p adsorb the active Isotopes to say appreciable extent, thus holding then in solution when tbs uranium precipitated. These particular metal# were chosen because data were available on the purification of uranium from them by Mans of the peroxide precipitation. gs® A uranyl nitrate solution containing 50 gas. of uranium was pre pared. 0.5 gm* each of Al444, Hg+4, and Fe444 (as nitrates) was added B? to It. The solution was made active by the addition of 5 mC of water boiler solution, made up to 500 nl volume, and allguotted for 0 count- The uranium was precipitated as uranium peroxide at pH 2.5 as described In Sxp. A (except that s small amount of c itric and malanle sclds was added to cosplex the Pe ). The UQ* was filtered out, ig nited to 00s, dissolved In sold, end ollquottcd for s second 3 count. A second precipitation mas then made to bring the Al, Mg, and Fa con tent to <10 ppm. Tbit final precipitate was converted to oxide, die- solved, and allquotted for the final 5 count. The procedure was duplicated without the addition oi tracer to provide blank values. Tbs corrected 0 results are given in Table 5. lvity Decontamination (Corrected), e/m Factor x 10° 1.09 x io8 1.6 m B.OO X io7 lA v < ... . .» : :. : i. : : j* t.... 1.. i .... mmm-.-:-,: sip® 1 1IJs Ifei' - '«*>* -%a££ss iisisiliiii M l In the second experiment, 0.5 *P« Meh of Sr, Ce, and Ce vere added as nitrates, end Rb as the chloride, to the solutions remaining from the first hold-heck carrierWM'Sm experiment in ea effort to replaee the active lone carried down by the uranium with their corresponding Inactive lone. Although e radio-chemical assay wee not made to deter mine the epee if lc isotopes supplying the major activity in water boiler solution, the literature Indicated 8r, Ce, Kb, end several rare earth Isotopes (of which It was hoped Oe wild be representative) to be among the principal offenders. Two successive peroxide precipitations were made at pB 2.5 on both the "hot" and "cold" solutions as In the case of the Al-Ng-fe experiment. The corrected 0 results are given In Table k. mm TABLE k Total 0 Activity Decontamination Sample (Corrected), c/n Factor ■m starting solution 8.00 x IO7 dissolution of first ppt. i.jo * io7 dissolution of second ppt. 1.50 * io7 D* A Systematic Study of the Decontamination Factors Obtained from —Successive Peroxide and Oxalate Precipitations at Various Aotl- vlty Levels. - 1. Three successive uranium peroxide precipitations mere made > WSM H WBfmw m i.*rffrl ... V ... I * .♦* IF if n * m m talnlng 50 gut. of urenlua and 0.5 nC of water boiler activity. 0 and r a ctiv itie s vere counted in itia lly and after each precipitation procedure erne duplicated on a similar "cold" solution to provide blank values. Htv starting solutions vere provided for identical studies at the $.0 and 50 aC levels. The corrected result! and decontamination fac tors appear In Table 5* 2. Three successive uranyl oxalate precipitations vere sada on a 500 ■! starting solution, X with respect to free SVO* (aa described in Bxp. B), containing 50 gee. of uraniua and 0.5 «C of voter boiler activity. This study vae also repeated at the 5*0 and 50 nC levels. The corrected result# sad decoataaination factors are given in table 5* 1. Decontamination Results Obtained vlth Successive Uranyl Oxalate I Precipitations under Xornal sad High Uraniua Yield Conditions, Using Pile "Dissolver" Solution as tbs Activity Source. These experiments vere done for two reasons: (1) to deteraln* b whether the physical characteristics end the activity of water boiler solution vere representative of dissolver solution froa a pile insofar as decontamination was concerned, and (8) to try to improve tbs uran lua yield with a slnlaua lose in decontaalnation efficiency. 1. A new starting solution vas made up vhich contained 50 gas of uraniua, 50 aC of dissolver solution, sad was normal vlth respect to fret nitric sold. It vas diluted to 500 si sad aliquotted for f and r counting. «« SECRET . i...... Ii3f : * s j.i V -. • -5 1 .'■' - %W- ilSillIf'lls v\‘.; <.' m^U MSfej p l S»-j‘v.Vj-JvV;‘*P* Tji- <>'• 1 Dreortiwinif •** Ftitort R*t*lv*i From F o t t t n ^tetiVcd From MB m m g Suce«M 0-5«C L e vel r.o mC Lt«f«l iO *C U w l arm C Uv«l iTo m l L«^«l 3T0mC Level ■ ..•••"ji—"- ■■'•,-> ne*i yu, w « l •/., T*t*l i/oL TWole/U, D r Dr J>r n * a «a , D r Dr 719*2 fc/- D r C*ff«W C»rricf»J Corrmtoi C r r r ttM CorrM J§tft S tk r tU q f#UKo* h u x t f — / .f f i v - 1.14*10* — L O U ti - t. o o n o — 3.74*1 f — ...... DtefMfeo/ h t u t o 9 / . J L l t J /0.J /.AJK I97 1.10*10* 4 . 4 t * t f M 3 J.A fM tO 7 AU lit * f t t .i 97 tw* ttlii*« fff f i . n t i * o-t f . i r n f 7 . 4 f t t f 1.1** t f A . t r * 10 /to ! 1*4 ** /.J A 7 4 / A .Z O ttO AO W A » *f r Ml*w* /.r h o * to7 i-ifM lO Al b io n to A .t o n t o h i f I f f /.s J * M U / . r / T .n i or — HI — — /*/ /7.I — 99/ — » — *fo* S t l r t i n q — A . d n o 7 - A M * to — — / . n t t o — U r t i f - S o ln le * a ti l l # Dlmlrtim tf lit /»rt **W A# I M i i f 1 4 A4 4 1 f t i f O .tA ltO * / i f 4 . i L l f A/0 • ••• P.iifi.f A» *f U fVt 3.01*1 f /./ A .0 4 H 0 7 o. t o.f 1.( 1* to* 4.0 f . f l t l O * 5T0 C m * 10* 7.3 P p f P v The uraniua vas precipitated at described la Exp. B, calcined to Uj Qq, dissolved la HRO^, made up to 500 ml, and aliquot ted for re counting of the 3 and r activity. The cycle vat repeated two sore tlaet and the entire procedure duplicated oa a "cold" solution to pro- . - i s i vide the retults thovn la Table 6. Uranlua yield results vert obtained by weight of the "hot" U30q; these yields Include transfer losses. 2, For tbs second experiment*, 200 si of 2 M uranyl nitrate solution, 2 R with respect to free HROs, and containing 50 mC of dle- oolver solution, was aliquotted for 3 and r counting. This solution vas heated to steam bath temperature and the uranlua precipitated by a 10# excess of hot, 50# oxalic acid solution. i\je precipitate vas digested hot for 1/2 hour with constant stirring. The slurry vas then chilled In an ice bath to 5-10°C and HOO ml of cold, saturated oxalic ' acid vas added. The chilled slurry v&a stirred for 10 minutes and then filtered. The cake vae transferred to a crucible for conversion to UsOg, which vas thsn dissolved and re-counted. The cycle vas re peated tvlce acre, duplicated on a "cold" solution, and uranium yield data taken on the "hotN IfeOg, as In the previous experiment. The re sults are given in Table 7. D ♦The uranyl oxalate precipitation conditions necessary to achieve maximum uranium yield were based on unpublished vork by J. P. Bertlno. i \ ‘.SECRET A .** .**...... : 8M : !*• .. I. • ...i yt : s:: ::• ••• •« j . ■ ; - I I ® w&p m i p m $ t I® f M M II i£’S i l l m m ss iXpSlt ss>« %w issiiiai1 8 1 ® ■?n x _ I N \-.c- i i * i s § c SHK MH l f e | I * s « s » m m m ;?©H 4;:-;^Sw--:-,i:!^ j j l g j WMM i s i m S S 8 fsl-.j mm TABLE 6 ■ m m ■ ■ I t a ® Uranium # ! S g l w m Wm T otal 3 Deconta T o tal r Deconta Yield "V/ *.=s? A ctivity, mination A c tiv ity m ination per Preci n Samole Corrected, c/m F actor Corrected, c/a Factor ta tlo n , j 8.69 x 10? ... 1.14 X 10 First ppt. 3.51 3 x 107 250 2.82 x 10 M Second ppt. 1.75 1 X 106 20 2.57 x 10 &v ! * £ Third ppt. 55.60 X 105 3.1 6.99 x 10 - Total for 5 cycleses 1 .6 x 10* TABLE 7 Uranium T otal 3 Deconta- T o tal r Deconta Yield A ctiv ity , mlnation A c tiv ity , m ination per Preci- Sam ple Corrected, c/m F actor Corrected, c/b F actor ta tio n , i i ® # IBB** S ta rtin g bo In . 1.04 x 1010 1.59 X 10 m p i « n p g M C n s &1M First ppt. 1.41 x 10 5.n x ur •*r ...... m m .... Second ppt. 5-23 x 10 J .98 X 105 l § i p KM Third ppt. p p t. 1.46 x 10^ 1.88 x 105 ■ B ; * Total for 3 cycles — 7.1 X 105 S s ■ : : I p g : i s t g ... S i a m m m-tm m m '8ms& M WM- m B § j j g fm I f i M h a g m n g l i f t msm Bras* » S i l ; m m 5 mm mm ,f i m m m KM a - - . mmm • ... 8ECRBT • fc:'- £*» y ^ | During « discussion of the problem vith Dr. 0. X. Rollefeon*, he suggested tbit some isotope# may exist in utter boiler solution as negative radiocolloids which would continually be carried down with the uranlua precipitate#. He further suggested that, if present, they night be renewed by the addition of positive colloids such er TiO#, ZrOa, or CeOi in a filtration step. Accordingly, the following expert- nents were tried: 1. Four 200 al aolutiona of dilute HflfO* containing 0.5 #C each of water boiler solution were allquotted for 3 and r activity. The pH of the solutions was then adjusted to 3.0, 2.0, 1.0, and 0, respec tively, by adding dilute HH^OH. After being alloved to stand at roan temperature for at least 22 hours, each solution vie slurried with 20 gas. of finely divided TiO*. The supernatant was filtered off and the . * ■ ■ ...... > • _ ■ procedure repeated twice vith 100 el portions of acidified wash water at the seat pH. The filtrate and washings were combined, allquotted, and recounted for 0 and r activity. The results any be found in Tablt 8. 2. A single 200 al dilute HHOj solution containing 0.5 #C of water boiler solution was aade up and allquotted for £ and y counting. ♦Consultant to tbe Chemistry -Metallurgy Division. About l/4 go. of sodlun silicate via added to tbs solution, and tba pH S w . • via adjusted to 5.5. At the end of 2k hour*, a nail mount of silica bad precipitated. The solution « b than filtered through a 3/8* ftaap cake of TiO* on a 150 nl floe, alntarad glass funnel, followed by two 100 al portions of sash vater at pH >.0. Tbs filtrata and sashlngs vira recounted for 0 and r activity. Thaos results are also given In lt t ls 8. TABLE 8 B R e s u l t s Standing Starting Soln, r n t n w s r * - «L Tine, hre. Activity, c/n Activity, c/a factor 3.0 22 8.52 x 107 7.85 * 107 1.09 F 4 4 2.0 23 8.86 x 107 8.15 x 107 1.01 F-l-c 1.0 u . 8.58 x 107 7.86 x 107 1.07 F-l*d 0 8.6} x 107 8.18 x 107 1.06 m F-2 5-5 26 8.60 X 107 8.25 x 107 1.04 r Results M - l (as above) 1.0) x 106 7.6J x 105 1.35 F-l*b 9.52 x 105 6,10 x 105 2.32 F-l«m 9-66 x 105 5.M X 105 t*T7 F-l-d 9.22 x 105 5.65 x IQ5 8.67 F-2 6.62 x 10s 5.80 x 105 1*14 -21- b ^ U 1 f* i F !*i Jr------. amBBBlBBpi I ™ ™ ' tS o §:S§lilllS ■ - Experiment A shoved that the decontamination of uranium with respect to the 0 activity in fission products is dependent upon the pH at which the peroxide reaction Is carried out* This la clearly shown by ths curve lu Figure 3. However, i t is known from a etudy of the uranium peroxide precipitation reaction (Report LA-IO89) that pH 1.0 is the highest acidity at which the precipitate can be conveniently han dled. It my be assumed, then, that a p decontamination factor of 10 (per cycle) Is maximum for the reaction. This value is not unprofit able snail i f i t could be repeated during subsequent cycles. This is not ths esse, at Exp. D shoved. Here, a constant factor was not ob mm tained during three successive precipitations at pH 1.0 at any activity .level, furthermore, the reaction provided for virtually no decontami nation from r activity. The decontamination efficiency of the peroxide precipitation was not improved by the use of hold-back carriers. The factors obtained in Sxp. C were negligible. At this point i t was concluded that ths uranium peroxide precipitation reaction had no decontamination value, and further experimental work was abandoned. With respect to the uranyi oxalate precipitation reaction, the results of Sxp. B were so encouraging that a systematic study of de contamination from various activity levels was immediately undertaken (Exp. D). By referring to TabLe 3, it is seen that decontamination val - 22- mPm obtained to belov the level of an equal quantity of noiml ur&nlua. (Also see the Saaple Calculatlona for the 0.5 XC level, page 7*) Total T decontamination was not as successful as total 0 reduction, but was V of the sam order of aagaitude. In Xxp. S It was found that the oxalate reaction was ssveral tlass less effective on solutions containing activity froa pile dissolver solution. The reason for this Is not known, although two suggestions for the difference In results have been offered: (1) that pile dis solver solution, being less pure than Los Alaaos water boiler solution, contained aooe colloidal silica which carried activity along with the precipitated uraniua, and (2) that the concentrations of the various active isotopes differed slightly between the two activity sources, so that, due to the individual decontaslnatloa characteristics afforded each speclts by the reaction, the total factors were also different. The decrease in total factors for tap. 1-2 as caapared to Exp. E-i is aore easily accounted for. In tbs case of high uraniua yield, the percentage separation of flltrats froa caM la considerably less per cycle than for the so-called "noraal" uranlua yield for the uranyl oxalate reaction. If suitable calculations were rads to correct for this difference, the factors froa Xxp. 1-2 and Sxp. E-l would probably coapare very favorably. Such calculations are not presented here be cause the necessary data were not taken. Radio-colloids do not w ear to exist to any appreciable extent in water boiler solution. The results of Kxp. F showed essentially m |®SptiS§®S8lS®^ no decroese in total 0 activity after attested reaoval of such col loids, although total r activity eas reduced by a factor of 2-3- This reduction la not vorth the effort aa cohered to 10r obtained directly by precipitation. Pile dlaaolver solution «s not tested for the presencs of colloid!. i iiiiiiiiffffflffflf BEKigHjH m m M mm mas s C w f l r a — agltiis M ...:;,V: ImI m m tm mm iM m ■,-. M . sir '? ,-? 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