LA-7553-PR

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Progress Report

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ClC-l 4 REPORT COLLECTION

REPRODUCTIONCOPY

Analytical Methods for Fissionable

Material Determinations in the

Nuclear Fuel Cycle

October 1, 1977—September 30, 1978

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.-

L%- LOS ALAMOS SCIENTIFIC LABORATORYPost Office Box 1663 Los Alamos, New Mexico 87545

AnAffismutiveAotion/EqualOpportunity Employex

#

,Thefour mostnxent reportsin thisseries,un-

classified,areLA-5696-SR,LA-6045$R, LA-6577-PR,andLA-7013-PR

‘Ilk workwassupportedby theUSDepartmentof Energy,Ofth of SafeguardsandSecurity.

This r.wrt w..pmp.md “ an account of work sponsoredby the Untied States Government. Netther the Umled Stitesnor the United .$t.les Department of Energv. nor .ny of Ihdr●mployees. nor any .( their .onlra. tors. :ubcontr. aom, ortheir employees. makes .W war .nty, txprts O, mjplifd. O,assumes .ny Iel.1 Ii.bihw or res~..xibdlty for the .CCU”CY.completeness. ?r usefulness 01 ●ny Monnatlo”. appdralus,product. or w...- disclosed. or represents Ih.t it. uw wouldnot infringe privately owned tichts,

UNITED STATESDEPARTMENT OF ENERGY

CONTRACT W-740 S-ENG. 36

Analytical Methods for Fissionable

Material Determinations in the

Nuclear Fuel Cycle

October 1, 1977–September 30, 1978

Compiled by

Glenn R. Waterbury

LA-7553-PRProgress Report

UC-15Issued: Janwxy 1979

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CONTENTS

ABSTRACT ,,, .0,,.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

I.

IL

III,

IV.

v.

VI.

VII.

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

DISSOLUTION OF NUCLE~WEL CYCLE MATERMLS . . . . . . . . . . . . . . . . . . . 2A. Teflon-Container, Metal-Shell Apparatus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2B. Gas-Solid Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3C. Laser-Enhanced Dissolution Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

ANALYTICAL METHODS AND AUTOMATED INSTRUMENTSFOR PLUTONIUM AND URANIUM DETERMINATION . . . . . . . . . . . . . . . . . . . . . 4A. Microgram-Sensitive Spectrophotometric Uranium Method . . . . . . . . . . . . . . . . . . 5B. Modification of Automated Spectrophotometer

for Microgram-Sensitive Uranium Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5C. Investigation of Microgram-Sensitive Uranium Method

with the Automated Spectrophotometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i’D. Development of Specific Controlled-Potential (klometric Method

for Plutonium and Construction of Automated Analyzer . . . . . . . . . . . . . . . . . . . . . 8E. Determination of Thorium and Uranium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9F, Determination of Thorium in Plutonium-Thorium Materials . . . . . . . . . . . . . . . . . 9G. Ion Exchange of the Elements in Hydrobromic Acid,

Hydriodic Acid, and Nitric Acid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

EVALUATION OF THE MASS-SPECTROMETRIC,ION-EXCHANGE-BEAD TECHNIQUE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

PREPARATION OF PLUTONIUM-CONTAINING MATERIALSFOR~ESALE PROGWM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..lO

PREPARATION OF PLUTONIUM-CONTAINING MATERIALSFOR THE NATIONAL BUREAU OF STANDARDS . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

PLUTONIUM ISOTOPE HALF-LIFE MEASUREMENTS . . . . . . . . . . . . . . . . . . . . .12A. Plutonium-239 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12B. Plutonium-240 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13C. Plutonium-241 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...13

PuBLIcAmoNs mDTALKs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..l3

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..l4

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iv

ANALYTICAL METHODS FOR FISSIONABLEMATERIAL DETERMINATIONS IN THE NUCLEAR FUEL CYCLE

OCTOBER 1, 1977—SEPTEMBER 30, 1978

Compiled by

Glenn R. Waterbury

ABSTRACI’

Work has continued on the development of dissolution techniques fordifficult-to-dissolve nuclear materials, development of methods andautomated instruments for plutonium and uranium determinations,preparation of plutonium-containing materials for the SafeguardsAnalytical Laboratory Evaluation (SALE) program, preparation ofplutonium materials for distribution by the National Bureau of Standards(NBS) as standard reference materials (SRMS), measurement of longerplutonium isotope half-lives, and analysis of SALE hranium materials. Newtasks include the development of methods and automated instruments forthe determination of thorium and uranium, and an evaluation of the ion-exchange-bead technique for the mass spectrometric measurement ofuranium and plutonium isotope distributions.

Completed tasks include the measurements of ion exchange distributionsof over 50 elements on cation exchange resins from nitric acid media andanion exchange resins from hydrobromic and hydriodic acid media. Using anewly developed procedure, the LASL automated spectrophotometer wasmodified to determine microgram levels of uranium and to determinemilligram levels of uranium and plutonium. Construction of an automatedcontrolled-potential analyzer for the determination of plutonium is nearingcompletion. Apparatus and procedures for the separation and complex-ometric titration of thorium and uranium are being developed.

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I. INTRODUCTION

Safeguards control of uranium, thorium, andplutonium in the nuclear fuel cycle requires inven-tory confirmation by adequate sampling andreliable analyses. Precise an”d accurate measure-ments of the amounts of these elements and theirisotopic compositions are required for widely diversenuclear materials, including pure products, reactor

fuels having complex chemical compositions, andmany types of scrap materials. Dissolutions andanalyses of materials containing highly refractorycomponents and of multiphase scrap are par-ticularly difficult.

Our objectives are toe develop fast, effective dissolution techniques

and analytical methods for plutonium, thorium,and uranium determinations.

1

. design and construct automated analyzers fordeterminations of the three elements.

● prepare well-characterized, plutonium-containing materials for use in the SafeguardsAnalytical Laboratory Evaluation (SALE)program and for distribution by the NationalBureau of Standards (NBS) and the NewBrunswick Laboratory (NBL).

● prepare, characterize, and distribute enrichedisotope plutonium materials for a Departmentof Energy (DOE) interlaboratory program tomeasure the half-lives of long-lived plutoniumisotopes and participate in the measurements ofsuch materials.

● prepare, characterize, and provide calibrationmaterials for the Los Alamos ScientificLaboratory (LASL) nondestructive analysis(DYMAC) system.

● evaluate correlation techniques for Safeguardscontrol of irradiated fuels.

● analyze inventory verification sampleschemically as requested by DOE.

II. DISSOLUTION OF NUCLEAR FUELCYCLE MATERIALS

Because many nuclear fuel cycle materials arerefractory in nature, their dissolution by conven-tional chemical techniques is difficult. Dissolutionis particularly difficult for recovery process residuesof fissile materials that have been incinerated andleached repeatedly with various hot acid mixtures inattempts to solubilize the uranium, plutonium, andthorium. A standard dissolution technique for suchmaterials is unlikely because of their diverse com-position.

Dissolution of nuclear fuel cycle materials beingprepared for assay and isotope measurements is of-ten the most difficult and time-consuming opera-tion. Use of conventional techniques, such as acidreaction at ambient pressureand molten salt fusionsin various combinations, often requires several daysto several weeks for complete dissolution of manymaterials. We are currently investigating the follow-ing techniques to attain rapid solubilization ofuranium, thorium, and plutonium: (1) mineral acidreactions at elevated temperatures in pressurizedcontainers, (2) gas-solid reactions with reactive

gases to decompose the material or to vcilatilizetheuranium, thorium, and plutonium, and (3) reactionswith various media using laser energy input.

A. Teflon-Container, Metal-Shell Apparatus(S. F. Marsh and J. E. Rein)

A ~ASL-developed Teflon container in a nickel orstainless steel metal shell has been used successfullyfor the dissolution of various nuclear materials.Maximum operating temperature and pressure ofthis apparatus were 270”C and 320 atm (5000 psi),respectively. The nickel shell was used with 3 to29A4HF, 3 to 12M HC1, and HF-HC1 mixtures withor without oxidizing acids such as 0.01 to O.lMHN08, 0.01 to O.llkf H,SO,, and mixtures of 3 to15.6Lf HNO, and/or 3 to 181kfH,SO, with or without0.01 to O.I..&fHF. LASL offered the design of this ap-paratus to several manufacturers, and the Parr In-strument Company began marketing slightlymodified models.

T%o years ago, we verified NBL’s findings thatventing problems frequently occurred with the Parrstainless steel models with Parr Teflon containerswhen used at 270”C with mixtures of 3 to 15.6MHNOS and 0.01 to 0.1A4 HF on such materials ashigh-fired PU02and calcined (U,PU)O,. Because theLASL-fabricated apparatus had given complete dis-solution at 270°C without venting, we speculatedthat the ventings in the Parr apparatus were due tothe Teflon undergoing a reaction at high tem-perature.

Six Parr containers, fabricated from anotherbatch of Teflon, were provided to us for evaluation,All but one of these containers also vented whenmixtures of 3 to 15.6A4HNOS and 0.01 to 0.lA4 HFwere used, even at a lower temperature of 250°C andin the absence of Pu02 and (U,PU)OZsamples. Inthe one container that did not vent, the stainlesssteel disk was badly corroded, indicating a high p~r-meability of the Teflon to HNO, and HF vapor.Tests were repeated for Parr Teflon containers withgold-plated disks. Although venting did occur, thegold-plated disks showed no corrosion, which in-dicated that the venting is caused by a pressure-producing reaction in the Teflon containers.

New Teflon containers were fabricated at LASLand tested. Although their failure rate at 250°C was

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2

comparable to that of the Parr-supplied containers,there were no failures at 230”C. Therefore, webelieve that 230”C will have to be the operatinglimit for these two supplies of Teflon containers. Wehave asked E. I. du Pent de Nemours & Co.,manufacturer of Teflon stock material, to providetechnical information for this application.

B. Gas-Solid Reactions (D, D. Jackson, J. E.Alarid, and J. E. Rein)

We continued our investigations of gas-solid reac-tions used to convert uranium and plutonium inrefractory materials to species readily soluble inmineral acids or to volatile species that condense asreadily soluble compounds in mineral acids such asHNO,. The reactions were carried out in a closedquartz tube in a temperature-controlled, resistance-heated furnace. The quartz tube provided con-trollable atmospheres and effective recovery of thesolubilized compounds.

We previously reported that chlorine and es-pecially carbonyl chloride effectively volatilizeduranium from uranium oxides and other nuclearmaterials.1 For example, 0.1 g of U80* volatilizescompletely with carbonyl chloride in 0.5 hat 1000°Cand in 1 h at 800°C compared to 12 h at 1000°C re-quired with chlorine.

Volatilities are being measured for variousmaterials present in nuclear fuel cycle materialswhen reacted with carbonyl chloride at 800°C. Zir-conium and niobium oxides volatilize completely in1 h; also, >99’%.of stainless steel powder and >41’%.of aluminum powder volatilize in 1 h. A verydifficult-to-dissolve, uranium-containing, scrapmaterial from a LASL waste-recovery calcinationfacility was reacted with carbonyl chloride. At1000”C, >75% of the material and >50% of theuranium volatilized in 2 h. Reaction of the residuewith hot HNOa dissolved the remaining uranium.Thus with this treatment, the uranium wassolubilized completely in several hours. In contrast,a treatment with HF-HNO~ mixtures in the Teflon-container, metal-shell apparatus and fusion of theundissolved residue with ammonium bifluoride didnot solubilize the uranium completely.

Other gases are being investigated for volatilizinguranium. Neither nitrosyl chloride (NOC1) nor an

equal-volume mixture of chlorine and nitric oxide(NO) was effective. Essentially no uranium wasvolatilized from UOZor USOSin 2-h reactions at 800or 1000”C. Tests show that nitric oxide suppressesthe chlorine volatilization reaction. Mixtures ofchlorine and higher oxides of nitrogen will be tested,A tube furnace being installed in a glove box will beused to investigate gas-solid reactions withplutonium materials.

C. Laser-Enhanced Dissolution Studies (M. E.Cournoyer, S. F. Marsh, and J. E. Rein)

Chemical dissolution treatments generally areenhanced by adding energy, Previously, heat hasbeen applied to acid solutions and to fusions ~withmolten salts. Gas-solid reactions at elevated tem-peratures, discussed above, are another example ofenergy input for chemical dissolution. It istechnically advantageous to dissolve material bytransferring energy directly to the material immer-sed in a reactive liquid or gas medium. Lasers haveample energy to vaporize materials, therebyproviding a reactive interface.

Initial efforts concerning laser applications haveinvolved acquiring safety information, making anextensive literature survey, and assembling test ap-paratus. There has been considerable study of theheating, decomposition, and volatilization of refrac-tory oxides using lasers. An absorbed energy of1 MW/cm2 was reported as necessary to vaporizeelements from oxides.9 Directly applicable to dis-solution is the laser heating of aluminum metal, im-mersed in a water-filled quartz cell, to >2050°C.s

A condition for laser-enhanced reactions is lowabsorption of the light energy in the medium.‘llansmittances over the visible wavelength range of400 to 700 nm were measured for HC1, HNO,, a 3/1HC1/HNO, mixture, and HC104. Light was absor-bed only in the HC1-HNO, mixture starting at 550nm and increasing rapidly toward the ultraviolet.Preliminary evaluations are being made of threelasers: (1) a 5-W, contiriuous-wave (CW), argon-ionlaser producing a beam of 480- and 520-nmwavelengths, (2) a 4-W neodymium glass laser witha 1.06-pm wavelength, and (3) a 1OO-J,pulsed, rubylaser at 694-rim wavelength. These lasers have been

3

TABLE I

DISSOLUTION OF ZrO, POWDER, A.1,0, POWDER,AND ZIRCONIA CRUCIBLE IN VARIOUS ACIDS

UNDER VARIOUS CONDITIONS

(Xmdition

Unheated solution

64-h reaction

64-h reaction plus0.5-h reactionin ultrasonicbath

Reflux heating,24-h reaction

Teflon-container,metal-shellapparatus,overnightreaction at250°C

Material

ZrO, powder

Al*O, powderZirconia crucible

ZrO, powderAI,O, powderZirconia crucible

ZrO, powderA1,O, powderZirconia crucible

ZrOZpowderA1,O. powderZirconia crucible

Percentage Dissolved in

16M HNO, 6M HC1 12M HC1 9MHBr

0.0

0.90.0

0.00.90.0

0.314.60.0

m---

---. . .

0.0

1.00.0

0.01.00.0

0.413.40.0

..-------

0.0

1.20.0

---------

0.415.00.0

100

10CI

0.0

0.0

1.00.0

0.01.10.0

0.39.60.0

10.6100

0.0

‘A dash indicates no tut was made.

used for tests on three refractory oxides: AIZ08pow-der, ZrO, powder, and large pieces of a crushed zir-conia crucible. The effectiveness of laser-enhanced,acid dissolution is being evaluated relative to aseries of progressively more vigorous reactions withthe same acids. The reaction conditions are reactionat room temperature with and without ultrasonicenergy, heating under reflux, and heating at 250”Cin the Teflon-container, metal-shell apparatus. Af-ter reaction, the extent of dissolution was deter-mined by measuring the dissolved aluminum andzirconium ions by complexometric titration. Theresults in Table I show that significant dissolutionwas obtained only in the Teflon-container, metal-shell apparatus. Laser bombardment, using the 4-Wneodymium glass laser, of the three materials in 6A4HC1and in 9i’kfHBr was unsuccessful in causing dis-

solution. Direct irradiation in air did not vaporizeany material, indicating inadequate energy. The1OO-J,pulsed, ruby laser will be evaluated next.

III. ANALYTICAL METHODS ANDAUTOMATED INSTRUMENTS FORPLUTONIUM AND URANIUM DETERMINA-TION

Our past efforts produced an automatedspectrophotometer4 for determining milligramamounts of both uranium and plutonium using ahighly selective method. We now have developed amethod for determining microgram amounts ofuranium and have modified the automated spec-trophotometer for its use in addition to the original

4

two methods. Diverse ion effects are being es-tablished for the microgram-sensitive uraniummethod using the automated spectrophotometer.We also developed a controlled-potentialcoulometric method for the selective determinationof plutonium. Fabrication of the automated instru-ment that will use this coulometric method isalmost complete. An apparatus for the complex-ometric titration of thorium and uranium has beenassembled, and procedures for the determination ofthese elements are being developed. Ion exchangedistribution data have been measured for 53 ele-ments on cation exchange resins from nitric acidmedia and for 58 elements on anion exchange resinsfrom hydrobromic and hydriodic acid media.

A. Microgram-Sensitive SpectrophotometricUranium Method (S. F. Marsh, N. M. Saponara,M. R. Ortiz, and J. E. Rein)

A method, described in Ref. 5, was developed forthe determination of microgram amounts ofuranium. This method consists of the extraction ofthe colored U(VI)-benzoyltrifluoracetone (BTFA)complex into butyl propionates from a solution thatcontains a Mg(II)-cyclohexanediamine-tetraaceticacid (CDTA) masking agent to provide highspecificity and hexamethylenetetramine (HMTA)and triethanolamine (TEA) to provide high buffer-ing capacity. The addition of a two-wavelength ab-sorbance measurement, one slightly down from the380-nm peak at 384 nm and the other at 400 nm forbackground correction, provided greater reliabilitywithout the need for a reagent blank reference.

The levela of metal and nonmetal ion tolerancesfor this revised method are given in Tables II andIII. The uranium level for this study was 0.20 pmol(48 pg). The diverse ions were added individually tothe uranium, beginning with a 1000:1 molar ratio. Ifa significant change at the %~0 confidence levelrelative to uranium alone was obtained, lower molarratios were sequentially tested. The tolerance formetal and nonmetal ions usually present in nuclearfuel cycle materials is excellent.

The absorbance response is linear for the 5- to 85-~g range of uranium, and the relative standarddeviation ranges from 2.9% at 5 pg to 0.2% at 85 ~g.

TABLE IILEVELS (MOLE RATIO TO URANIUM)

OF NONINTERFERING METAL CATIONS

1000:1 100:1

AgCdCsCuGeHgKLaMgNaY

B Mn(II)Ba NiBi PbCa RbCo SrFe ScGa ThIn T1Li Zn

10:1 1:1

Al Ce(IV)Au PdBe SnCe(III) TeCr(III) TiCr(VI) VHfMn(VII)MoPtRuSbSeZr

The correlation coefficient for a linear least squaresfit of 30 measurements over the 5- to 85-~g rangewas 0.9998 with a relative standard deviation of theresidual about the line of 0.70%.

A paper describing this method has been acceptedfor publication in Analytica Chimica Acts.

B. Modification of Automated Spectro-photometer for Microgram-Sensitive UraniumMethod (D. D. Jackson, R. M. Hollen, and J. E.Rein)

The automated spectrophotometer, originallydesigned for the determination of 1 to 12 mg ofuranium and plutonium, was evaluated for thedetermination of 0.12-to l-mg amounts of uranium,without instrumental or procedural changes.a” Thestandard deviation was a constant 0.013 mg overthis range, which corresponds to 10.4 relative per-cent at the 0.12-mg lower limit.

A main application of the instrument is foranalyzing uranium-containing scrap materials,most of which have low amounts of uranium andhigh amounts of extraneous elements. Because of alow-milligram limit and a maximum sample volume

5

TABLE III

LEVELS (MOLE RATIO TO URANIUM)OF NONINTERFERING ANIONS

\

1000:1 100:1 10:1 1:1— —

Acetate Nitrate EDTA’ Oxalate PhosphateBromide Sulfide FluorideBromate Sulfite IodideChloride SulfateIodate SulfamateNitrite Thiocyanate

‘Efhylenediaminetraaceticacid.

of 0.5 ml, low-level uranium samples were analyzedby evaporating larger volumes in the sample tubesand dissolving the residues in 0.5 ml of 8ikfHNOS.Complete dissolution may not be attained for sam-ples containing high amounts of salt. Also, the un-dissolved residue may retain small amounts ofuranium.

The instrument was modified for use with themicrogram-sensitive uranium method, as discussedin the previous section. The instrument maybe usedto determine milligram levels of uranium andplutonium using the original method and to deter-mine microgram levels of uranium. Instrumentmodifications include (1) three new reagent dis-pensers for the microgram-sensitive uraniummethod, (2) a mechanism to switch the pneumatic-hydraulic system automatically between the originalset of dispensersfor the milligram-sensitivemethodsand the new set of dispensers, (3) removal of cam-actuated switches driven by a common shaft thatcontrolled mechanical operations for the milligram-sensitive methods and expansion of the microcom-puter system to provide complete controls of allmechanical and electrical operations, (4) installa-tion of a pair of interference filters for absorbancemeasurements at 384 and 400 nm for themicrogram-sensitive method, and (5) replacementof the 3-1/2-digit, analog-to-digital converter with a4-1/2-digit converter to cover a largerdynamic rangefor the microgram- and milligram-sensitivemethods. These modifications required rewiring of

many instrument systems, computer hardware ad-ditions, and software additions and changes.

No change was necessary in the 12C0rpm stirringmagnet mechanism. Extraction of the V(VI) -BTFAcomplex into the butyl-propionate organic phasewas greater than 99.5°Ain 6 min and droplet spatter-ing was insignificant. The aqueous and organicphases separate in less than 1 min to produce a clearorganic phase. No changes were necessary for thelight source and photodiode detector. Light baffles,added to the pair of filters used for the microgram-sensitive method, decreased the output signal fromthe photodiode to the range obtained for themilligram-level methods, thereby decreasing thedynamic range of current to be handled in the dataprocessing system. The procedure for themicrogram-sensitive uranium method is to transfera magnet stirring bar and a maximum of l-ml ali-quot of sample into a tube, to place as many as 24tubes on the instrument’s turntable, to set a switchthat selects instrument operation for themicrogram-sensitive uranium method, and to in-itiate the automated operation. At the first station,a dispenser delivers 5 ml of a buffer-masking solu-tion consisting of 2.15ikf HMTA, 0.75A4TEA, and0.08it4 Mg-CDTA complex; a second dispenserdelivers 3 m,C of a 3% BTFA-butyl propionateorganic solvent; then the phases are mixed for 8min. At the second station, 11 m,Cof a 2.8A4HMTAsolution ia dispensed to raise the organic phase to a

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,

,

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6

clean area of the tube. At the third station, absor-bance of the organic phase are measured at 384 and400 nm. A paper tape printout shows (1) a four-digitnumber, proportional to the difference of the absor-bance at the two wavelengths, that is proportionalto the quantity of uranium, (2) a number from 1 to24 that identifies the tube position on the turntable,and (3) a two-digit number that designates that themicrogram-sensitive uranium method was used.The throughput rate of 8 min per sample is set bythe time required for mixing of the aqueous andorganic phases.

Although the aqueous and organic phases dis-engage well, aqueous phase droplets adhere to thetube wall in the organic phase region. Raising theorganic phase to a clean area of the tube providesunbiased absorbance measurements. An unexpec-ted difficulty was finding a phase-raising solutionthat did not affect the absorbance of the extractedcomplex, but that had suitable density and viscosityfor delivery control, and was inexpensive and simpleto prepare. Of more than 10 solutions tested, a 2.8MHMTA aqueous solution met the above require-ments best.

C. Investigation of Microgram-SensitiveUranium Method with the Automated Speo-trophotometer (N. M. Saponara, R. M. Hollen,D. D. Jackson, and J. E. Rein)

In the manual-operation method for determiningmicrogram quantities of uranium, we adjust thesolution pH between 5.6 and 5.7 before adding theorganic solvent. Because an automated pH adjust-ment is difficult, the effect of acid was determined.Extensive tests of diverse ion effects are being made.

The effect of acid was determined for Oto 12milli-equivalents (meq) of HNOS for 2.5 to 150 yg ofuranium. Experimental acid levels used were O,1,3,6, 9, and 12 meq. We obtained the O-meq level byevaporating uranium calibration solution aliquotsto dryness and dissolving the residues with water.

For each of the six acid levels, a calibration equa-tion was computed by a least squares fitting of theoutput values, which are proportional to absor-bance, vs micrograms of uranium. The outputresponse for the 1-, 3-, 6-, and 9-meq acid levels was

linear for the 2.5- to 100-~g uranium range. At 12meq of acid, the response was low and erratic. At Omeq of acid, the response generally was 5°A lowerthan for the 1 to 9 meq of acid for the entire uraniumrange. Standard deviations at the 1-, 3-, 6-, and 9-meq acid levels were similar, ranging from 0.5%

above 90 #g of uranium to 3% for 5 #g of uranium. Atthe lower limit of 2.5 Kg of uranium, the standarddeviation was about 10%.

The output generally decreases with increasingacidity. Although the calibrations tend to convergeat increasing uranium levels, there is only a slightdifference at 100~g. At the acidity extremes of 1 and9 meq, the output difference equals about 1 yg ofuranium from 50 to 5 pg of uranium. At higheruranium levels, the output difference decreases to<0.5 pg of uranium.

For maximum accuracy, we use a calibrationequation in which the acidity level matches that ofthe samples. Use of an “average” calibration equa-tion computed from the data for the 1-to 9-meq acidrange gives maximum deviations of 5% for the 10- to100-~g uranium range and 10% at 5 gg of uranium.

We are now investigating the tolerances of metaland nonmetal ions on the automated instrumentanalyses. Because the tolerances can be a f%nctionof acidity, they are being measured at 1 and 9 meq ofacid (as HNOJ. Results obtained in the nearly com-plete investigation of metal cations in 1 meq of acidgenerally agree with those observed for the manualmethod (Tables II and III). The automated spec-trophotometer procedure, like the manualprocedure, generally is applicable to several nuclearfuel cycle materials, including scrap materials.

Because butyl propionate is expensive, this sol-vent is purified and reused. Distillation alone is notsufficient. The absorbance of the distilled butylpropionate is slightly high in the 380- to 425-rimregion and causes a positive bias for uranium. Also,the reagent turns yellow soon after the BTFA is ad-ded. Satisfactory results are obtained by distilla-tion, followed by treatment with activated charcoaland a final flow through an alumina column. Blanksand uranium samples ‘processed in the automatedspectrophotometer with reagent prepared fromrecovered butyl propionate are similar to those ob-tained using fresh reagent.

D. Development of SpecW1cControlled-PotentialCoulometric Method for Plutonium and Con-struction of Automated Analyzer (D. D. Jackson,R. M. Hollen, F. R. Roensch, and J. E. Rein)

Our objective is to develop an automatedplutonium analyzer whose features include hightolerance to impurity elements present in nuclearfuel cycle materials, measurement of low-milligramlevels of plutonium, and measurements having only0.1 to 0.2% relative standard deviation. A versatileinstruments’e used for investigating electrometricsystems for determining plutonium will serve as themodel for our automated instrument. It is centeredaround a programmable calculator that controlstitration conditions and’ monitors pertinentvariables.

A controlled-potential coulometric methoddeveloped for plutonium features high specificity, aprecision of abdut O:1% relative standard deviationat the 5-mg plutonium” level, use of simply con-structed cells, ati”dop~tatlonalsimplicity for adapta-tion to an autoriiiited instrument.o;’ Plutonium isreduced at O.~!$~ (VS$C~)” to 1%(~’ in 6.~~H~l-0.015M”sulfarnic ticid electrolyte. Diverse ions areoxidized at a potential of 0157V, whereas Pu(III) isnot significantly dxidized’. J!kosphate (as ~a,~o.)is added to lower the Pu(~-Pu(~) potential, andPu(III) is oxidized by titration to Pu(IV) at O.@ V.Results of a detailed investigation of diverse ion”ef-fects for mof6 than” ‘i% metal ions and’ nonmetalanions ar5 destx’ibed in Refs. &and’9. ~etal cationsnormally pf&i&it in rititleat fuei cycle materials d“onot interfere at an bqual mole ratio relative to 0.02mmol (5 m’g) ~f plu~o’h~urn.ktdrference & d-efinedas a change significant at the 95% confidence levelrelative to p’iii~ plutohiurn. Most potentialityinter-fering nonmbtal ani~qsi, ~uth as fluoride, areremoved by piifchlofic tic~d Fuming. fiecauseuranium often i~ pre.Wit iii fdutoniurn-containingmaterials, iti ~ftect a~so was investigated. l?ive-milligram aliqtititi of a piutonium standard sofu-tion, with and without ikided uraniuiii tip to a M to1 molar Mitioreiative to piutonium, wet~ ptocessedconcurrently with and without ah initiai perchloricacid fuming. Statistical “t” tests skewed no effectsfrom the uiiiiihiiii tit the 93% confidence level forany test condition.

During otiht.estii% bbserved that for some futnedsamples, a long thii~ i%i+hi~quired to reduce the

plutonium to Pus+ in the coulometric analysis andthe plutonium results were low. Further investiga-tion showed that this occurred when the sampleswere heated beyond “just dryness.” The bakedplutonium residue may still be dissolving in the5.5i2f HC1-O.015A4sulfamic acid electrolyte duringthe initial reduction. Methods for treating thefumed residue to overcome this effect are being in-vestigated.

To characterize the plutonium content of SALEmixed-oxide materials (see Sec. V), 5-mg aliquots ofa plutonium standard solution were processed dailyfor 6 days. The computed relative standard devia-tion was O.llYO.

In addition to controlling the electrolysis and datatreatment, the programmable-calculator-centeredapparatus will control all mechanical operations.The basic, simple design of the mechanical opera-tion will provide long-term, trouble-free use. Theanalyst delivers sample aliquots into cells andplaces up to 24 cells on the instrument’s turntable.The turntable automatically rotates the cells to onestation where reagentsare added and the controlled-potential electrolysis takes place. The results, alongwith a cel~ identification number, are given on apaper-tape printout. The spent sample solution istransferred to a plutonium recovery bottle, the cellcomponents are rinsed, and the rinses also arerecovered.

Most of the mechanical components for theautomated”instrument have been built and tested.The entire instrument, designed to fit in a slopingfront glove box, is being assembled. The electroniccomponents will be located outside the glove box,but the mechanical components, fabricated ofmaterials to resist acid corrosion, will be inside thebox. A 15° Geneva-drive mechanism providessmooth, accurate rotation of the aluminumturntable to ensure correct angular positioning. Alocking mechanism driven by a pneumatic cylinderengages tapered indentations in the turntable rim ateach of the 24 positions.

At the measurement station, the electrodes,stirrer, afid tubes tl@ deliver nitrogen gas, reagentsolutions, and rinse solution are rigidly positioned inti~eilon support. Upon arrival, the cell is raised by apneumatic-cylinder-driven assembly and sealed‘@ainst the Teflon support. The simple and inex-pensive cells are fabricated by flame-sealing a flatglass bottom onto a piece of 48-mm glass tubing.

●

✎

8

The reagent dispensers for the HC1-sulfamic acidelectrolyte and the phosphate complexant aresimilar to those used in the automatedspectrophotometer.4 Only the glass, Teflon, andKel-F come in contact with the highly corrosivereagents.

The rinse solution is withdrawn by suctionthrough a Teflon tube that is lowered through aTeflon guide tube mounted in the Teflon support.The delivery tube is driven by a pneumatic-cylindermechanism to an exact position at the bottom of thecell, necessary for effective rinsing of the platinumgauge electrode. Preliminary tests indicate that tworinses are adequate.

Mechanical operations will be controlled byphotoisolated relays actuated by the programmablecalculator. These relays avoid interference of logiclevel signa~s of the calculator caused by voltagetransients from the power solenoids.

E. Determination of Thorium and Uranium(S. F. Marsh, M. R. Ortiz, and J. E. Rein)

Based on techniques that were readily adaptableto automated analyzers, we developed a newmethod for the determination of thorium anduranium in fuel cycle materials. An attractivetechnique is complexometric titration to aphotometric endpoint, and a low-cost apparatus wasassembled for this purpose. The chemistry is simple.A metal-indicator complex, with a different colorthan that of the uncompleted indicator, is titratedwith a strongercompleting agent. The color changescontinuously as the metal-indicator complex is con-verted to the uncompleted indicator, after whichthe intensity of the uncompleted indicator colorremains constant.

In the apparatus, the completing agent titrant isdelivered at a constant rate from a motor-driven,high-precision micrometer pipet. A sensing probeimmersed in the solution being titrated transmitslight intensity through a fiberoptic guide to an in-expensive calorimeter connected to a strip-chartrecorder. The recorder and motor-driven pipet aresynchronized to provide a plot of changing color in-tensity correlated to titrant volume.

Initial studies (see Table IV) show that 100 pg ofthorium are titratable to a precision better than 1%.The indicator used is xylenol orange, the strong com-

TABLE IV

TITRATION OF THORIUM-XYLENOLORANGE COMPLEX WITH DTPA

ThoriumTitrated

(pg)

59

23467093

139

DTPAMolarity

RelativeStandardDeviation

(%)

O.00010.00010.00050.00050.00050.0010.001

5.86.12.21.71.00.60.7

plexing titrant is diethylenetriaminepentaaceticacid (DTPA), and the medium is 0.05A4HBr.

Separation procedures for uranium and thoriummixtures arid a titration procedure for uranium arebeing developed. Procedures will be investigated formilligram levels of thorium and uranium applicableto unirradiated fuels and for microgram levels”ap-plicable to highly radioactive, irradiated fuels. Theapparatus is well suited for shielded glove boxoperation.

F. Determination of Thorium in Plutonium-Thorium Materials (L. F. Walker and D. S.Temer)

A complexometric titration method was appliedto the analysis of plutonium-thorium materials byseparating the plutonium, which otherwise inter-fered in the titration. The plutonium was removedfrom a 1’2MHCI solution of the sample with BioRad(Dowex) 1 x 2 anion exchange resin while thethorium passed through, Perchloric acid was addedto the eluant solution, which then was fumed todryness to remove HC1 and some organics. Theresidue was dissolved in water and the thorium wastitrated with tetra-sodium EDTA standardizedsolution. The pH was maintained at 2.5 + 0.1 dur-ing the titration; the color indicator was xylenolorange. Studies of the effects of several other ions on

9

..

the determination of thorium are being made using1 and 0.1% of the foreign ion relative to the thorium.Iron removed with the plutonium on the resincolumn did not interfere at the l% level. Phosphate,sulfate, zirconium, and cerium, which do not inter-fere at the 0.1% level, are being tested at the l%level relative to thorium.

G. Ion Exchange of the Elements inHydrobromic Acid, Hydriodic Acid, and NitricAcid (S. F. Marsh, J. E. Alarid, C. F. Hammond,M. J. McLeod, F. R. Roensch, and J. E. Rein)

References 10 and 11, respectively, presentcation-exchange distribution data for 63 elementsbetween 3 and MM HNOS and three strong acidresins having 8Y0, 40A, and macroporous crosslinkages and anion-exchange distribution data for58 elements between 0.1 and 8.7M HBr and between0.1 and 7.4M HI and three strong base resins havingthe same percentage of cross linkages. Separationsapplicable to the chemistry of nuclear fuel cyclematerials are described,

IV. EVALUATION OF THE MASS-SPECTROMETRIC, ION-EXCHANGE-BEADTECHNIQUE (R. M. Abernathy, S. F. Marsh,J. E. Alarid, and J. E. Rein)

The mass-spectrometric, ion-exchange-beadtechnique, developed by the Oak Ridge NationalLaboratory (ORNL),’2 is being evaluated by ORNLand the International Atomic Energy Agency(IAEA) Safeguards Laboratory for the determina-tion of uranium and plutonium in reprocessingplant input samples. Using mass spectrometersequipped with pulse-counting detectors, we canmeasure low-nanogram quantities of uranium andplutonium on a single ion exchange bead loaded on asingle rhenium filament. We are using a thermalionization mass spectrometer to evaluate the sen-sitivity of the technique. The spectrometer, madeby Ion Instruments Inc., has a triple-filamentsource, Z-focusing, and interchangeable Faradaycup and electron-multiplier detectors. Only themore sensitive electron-multiplier detector wasused.

For these evaluations, an aliquot of the sampledissolver solution is combined with about 10 beadsof Dowex-1, X2, 50-100 mesh, anion exchange resinin 8M HNOS. In 48 h, without agitation, about halfof the plutonium and 0.0570 of the uraniumreportedly sorbs on the resin beads, With an initial100/1 uranium/plutonium ratio and an appropriateamount of dissolver solution, 1 to 5 mg of plutoniumand 0,.1to 0.5 ng of uranium are sorbed per bead. Asingle bead is transferredto a rhenium filament thatis crimped, placed in the source of the mass spec-trometer, and heated by current to destroy the bead.Current is increased and the plutonium spectrum isrecorded. After increasing the current further, theuranium spectrum is recorded.

Our measurements showed that the sorption rateof plutonium onto 10 Dowex-1, X2, 50-100 mesh ionbeads from 0.1 ml of 8M HN08 containing 600 ng ofplutonium was 30% complete in 15 min and 75%complete in 4 days. The mass-spectrometric sen-sitivity of ion-bead loading was compared to ournormal loading technique of evaporating plutoniumsolution on a side rhenium filament using single ionbeads on both center and side filaments. There wasno significant difference between the sensitivities ofthe two ion-bead loading positions or with the sen-sitivity of our normal loading technique. Aminimum loading of about 35 ng of plutonium isused to attain accurate measurements of minorisotopes. If only the major ‘SePuand 2’OPuisotopesare measured relative to an added 242Puor ‘44Puspike, the estimated minimum quantity of sampleplutonium is 5 ng. The sensitivity of the techniqueused for uranium measurements is being evaluated.

V. PREPARATION OF PLUTONIUM-CONTAINING MATERIALS FOR THE SALEPROGRAM (J. W. Dahlby, L. C. Haynes, D. D.Jackson, S. F. Marsh, F. R. Roensch, D. J.Temer, J. E. Rein, and G. R. Waterbury)

Three batches of high-density 3/1uranium/plutonium mixed-oxide pellets are beingcharacterized at NBL and LASL for distribution assemimonthly SALE materials. Individual pellets,225 from each batch, were sealed in glass ampoulesunder a dry argon atmosphere to attain long-termstability.

10

We characterized the uranium and plutoniumcontents using two different methods for each ele-ment. The NBL-modified Davies-Gray titrimetricmethodla and controlled-potential coulometry withsulfuric acid electrolyte’ were used for uranium.Controlled-potential coulometry with sulfuric acidelectrolyte and with hydrochloric acid electrolyte(Sec. 111.D) was used for plutonium. We charac-terized the uranium and plutonium isotope dis-tributions by thermal ionization mass spectrometryfollowing ion exchange separation of the twoelements.” Appropriate NBS standard referencematerials (SRMS) were processed concurrently withthe pellet samples for all analyses. The charac-terization results were computed relative to theresults obtained for the NBS SRMS, usingguidelines presented in a US Nuclear RegulatoryCommission document.”

New batches of plutonium oxide powder are to beprepared and characterized for distribution assemimonthly SALE materials. Previous batchesconsisted of materials heated in air at 900”C topromote stability relative to sorption of atmosphericmoisture. A study of their stability has shown that,after a 2-month exposure to atmospheres withrelative humidities up to 850A,their initial composi-tions can be restored by heating at 11O”Cfor 24 h.Recently, another batch of plutonium oxide heatedat 950°C in air was found to sorb and desorb waterwhen cycled in 50% relative humidity air and placedin a desiccator. Weight changes of 0.04% were ob-tained in 15 min. Further heating to 1250”C gave astable material having < 0.002% weight changes. Inthe United Kingdom, 1250”C calcined plutoniumoxide is used as a reference material with a claimedO/M ratio of 2.000 and long-term stability.” A dis-advantage in using 1250°C calcined plutonium ox-ide in the SALE program is its greater resistance todissolution than oxide calcined at lower tem-peratures, normally encountered in the US nuclearfuel cycle. The 1250”C calcined plutonium oxide didnot dissolve completely in a heated mixture of 16A4HNO, and 0.03A4HF at ambient pressure,but it diddissolve completely in this mixture when heatedovernight at 230°C in a Teflon-container, metal-shell apparatus. A 24-h reaction time was requiredto dissolve it in a HC1-HNOS-HFmixture in a sealedreflux tube.i’

Samples to be considered for preparation, charac-terization, and use as SALE plutonium oxide in-clude the following.1.

2.

3.

VI.

bw-temperature ( -5500C) calcined material,typical of US processes, can be used on a totalplutonium content per container basis. Disad-vantages are characterization uncertaintiescaused by possible heterogeneity of sorbedwater, the need for the analyzing laboratory toquantitatively remove the material from itscontainer, and the by-passing of the error com-ponent of weighing in the analyzing laboratory.The past practice of using 900 to 950”Ccalcined material can be continued. Disadvan-tages are that the analyzing laboratory mustheat the material to restore its original charac-terization composition and the uncertainty ofthe restoration after long storage periods.Use of 1250”C calcined material, whichprovides long-term stability, has the disadvan-tage of requiring a more vigorous dissolutiontreatment than process material. However, itsstability permits it to be packaged on bothgram plutonium per gram material and gramplutonium per container bases, therebyproviding a means to assess error componentsin the analyzing laboratories of sampleweighing and of quantitative removal from thecontainer.

PREPARATION OF PLUTONIUM-CONTAINING MATERIALS FOR THENATIONAL BUREAU OF STANDARDS (G. R.Waterbury and staff)

Batches of low 24”Pu(-4%) plutonium metal havebeen prepared, characterized, and packaged for dis-tribution by NBS as SRM 949. Plans have beenmade to prepare another batch of this material. Weare now preparing a 2UPUSRM, to be certified forthe number of 2UPUatoms per container, for use inisotope-dilution, mass spectrometry (IDMS)measurements. The IDMS technique is usedworldwide for the determination of uranium andplutonium. The desired isotope for addition as thespike is one present at very low levels or not at all inthe sample. The usual spike for plutonium analysis

is 242Pu,but as plutonium is recycled and irradiatedto higher burnup, the Z42pucontent increases and

this isotope becomes less suitable as a spike.The preferred spike, which is produced by double

neutron capture on Z4Zpu, is the heavier 244Pu

isotope, present only at trace levels. Its productionis limited by the short, 5-h half-life of 24EPu.Specialhigh-flux irradiations in,the ORNL research reactorand subsequent separation in a calutron haveproduced several grams of -98% enriched 244Pu.About 1 g has been allocated for distribution byNBS as a SRM, with 1 mg per container certified forthe number of 244Puatoms.

Packaging of this material is in progress. A solu-tion of the dissolved 244Puoxide was distributed byweight into 4-02 Teflon bottles, followed by ovenevaporation to dryness. The Telfon bottle provides aconvenient means for a laboratory to prepare theX.pu spike.The bottlewith its evaporated residue is

weighed, acid is added, the residue is dissolved, andthe bottle with solution is weighed to provide data tocalculate the atoms of 244Puper gram. The preparedsolution can be distributed by weight into a seriesofcontainers for use as spikes. The assay and isotopic-distribution characterizations on random sampleswill be done by NBS, NBL, and LASL. The “Poly-seal’’-type bottle lids consist of hollow cones ofpolyethylene in a bakelite screw-cap. A thin piece ofTeflon, placed over the “Poly-seal,” to collect anyplutonium particles scattered during storage andtransportation, is simply pushed into the bottle bythe user. The bottles containing evaporated residuewere tested by vigorous shaking and repeated 3-mfalls.

Variablea investigated in establishing the packag-ing scheme were the acid medium composition ofthe 244Pudistributed to the Teflon bottles, themeans of evaporation, and the composition of theacid necessary to attain complete solubilization ofthe evaporated residue. The solubilization wasdetermined by filtering to collect any undissolvedplutonium, rinsing the bottle twice with the sameacid medium used to dissolve the residue, andfinally cutting the Teflon bottles into sections.These sections, as well as the filter, were assayed forplutonium by alpha-particle counting. The adoptedscheme that gives >99.995Y0solubilization is an 8MHN08-0.01M HF mixture as the medium of the

Z44pu solution distributed to the Teflon bottles, ovenevaporation at 80°C, removal of trace moisture athigh vacuum, and solubilization of the residue withthe same 8M HNOa-O.OIMHF acid mixture.

VII. PLUTONIUM ISOTOPE HALF-LIFEMEASUREMENTS (G. R. Waterbury and staff)

The Half-Life Evaluation Committee (HLEC),consisting of representatives from the ArgonneNational Laboratory (ANL), LASL, LawrenceLivermore Laboratory (LLL), Mound Laboratory-Monsanto (MLM), NBS, and the Rockwell Inter-national Rocky Flats Plant (RI-RFP), is organizingan effort to measure accurately the half-lives oflonger lived plutonium isotopes. Toward this effort,LASL is (1) preparing, characterizing, and dis-tributing batches of high-purity plutonium fromspecially provided, enriched isotope materials, and(2) determining the half-lives using the IDMStechnique for measuring the produced daughterisotope. The LASL characterization measurementsinclude assay, isotopic distribution, metal im-purities including other transuranics, and nonmetalimpurities.

Measurements of the ‘3’Pu half-life are completedand articles have been accepted for publication in atechnical journal. A batch of enriched 24”Puhas beenreceived, and measurements of the *’iPu half-life arein progress at five laboratories. An ANL measure-ment of the 2saPuhalf-life of 87.71 + 0.03 yr agreesclosely with the MLM measurement of 87.77 + 0.03yr. The HLEC recommends adoption of the averageof 87.74, with an uncertainty of +0.04 yr.

A. Plutonium-239

Our two papers “Preparation and ChemicalCharacterization of Plutonium-239 Metal Used forHalf-Life Measurements’”a and “Plutonium-239Half-Life Determined by Isotope-Dilution Mass-Spectrometric Measurement of Grown-In Uranium-235’”9 will be published in a special issue of the In-ternational Journal of Applied Radiation andIsotopes.

12

B. Plutonium-240

A recent ANL measurement of the ha~-life of24”Pu,based on alpha-particle counting, of 6569 @“is much higher than the present American NuclearStandards Institute’s (ANSI) recommended valueof 6537 yr.zi The HLEC has recommended that anew measurement of the half-life of this isotope bemade by the participating laboratories. A 28-gquantity of 98.3%-enriched ““Pu was received andwill be used in the form of the stable oxide becausereduction to metal cannot be undertaken at LASLfor several months. Another form considered is thestoichiometric PU(S04)Z.4 HZO,Z but initial workwill be done with the oxide. Chemical characteriza-tion provided with the material indicated a “Amcontent of O.12% and a uranium content of 0.057~0.Because these and other impurities would cause un-certainty in the half-life measurements determinedby calorimetry, alpha-particle counting, or IDMS ofdaughter “W, the entire quantity of 24”Pu waspuritled.

The ““Pu0, was dissolved in a 15.7A4 HNO,-0.02M HF solution, the solution was filtered toremove a silica residue, the filtrate was adjusted to7.2M HNOa, and the plutonium was sorbed on acolumn containing 400 cmg of Dowex-1, X2 anionexchange resin.‘s The column was washed with 7.2A4HNOS until the ‘{Am and ‘“U activities in the ef-fluent decreased to low and constant levels, in-dicating equilibrium between their formation andelution. Monitoring showed that the effluent did notcontain 24”Pu.The plutonium then was eluted with a0.39Al HNOa-0.01A4HF solution, the solution wasevaporated slowly to dryness, and the residue wascalcined to PuOZat 1250”C and blended to promotehomogen~ity.

Chemical analyses of the ignited and blended24”Puoxide show a total impurity content of 600ppm. About 200 ppm consisted of iron and otherstainless steel components, apparently introducedby the container used to blend the ignited ““Pu ox-ide. The other major impurities, chloride andfluoride, were reduced to <10 ppm by pyrohydrolyz-ing the material. It then was reignited at 1250°C.

Plans are being made by W. Strohm of MLM andChairman of the HLEC for the interlaboratorycharacterization and half-life measurements of the

material. If the characterizations show that thematerial is satisfactory, it will be packaged accor-dingly and distributed to the various laboratories,

c. Plutonium-241

Three years ago, measurements were started on amixture of highly enriched isotopes of 24iPu andZ.Zpuat a ratio of ~ 1.27 to 1. The “lPu half-life is be-

ing determined from the decreasing ratio of241PuF42Pumeasured at 6-month intervals by ther-mal ionization mass spectrometry followingchemical separation of “lAm. Portions of the mix-ture were distributed to LLL, MLM, NBS, and RI-RFP for measurements.

Our most recent values for the 24’Puhalf-life, us-ing two mass spectrometers, were 14.38and 14.41yr.These values were computed from four different fila-ment loadings on each instrument for fourplutonium fractions of the 24Tu-242Pumixture. Theonly data reported by other participatinglaboratories have been the first 241Pti42Puratiomeasurements by MLM and very preliminaryvalues by RI-RFP. The computed ‘lPu half-life, us-ing the MLM value and our initial measurement ofthree years ago, is 14.4 yr.

PUBLICATIONS AND TALKS

D. D. Jackson, R. M. Hollen, S. F. Marsh, M. R. Or-tiz, and J. E. Rein, “Determination of SubmilligramAmounts of Uranium with the LASL AutomatedSpectrophotometer, ” in Analytical Chemistry inNuclear Fuel Reprocessing, W. S. Lyon, Ed., Proc.21st Conf. Anal. Chem. Energy Technol., Gatlin-burg, Tennessee, October 4-6, 1977 (Science Press,Princeton, 1978), p. 126.

D. D. Jackson, R. M. Hollen, F. R. Roensch, and J.E. Rein, “Highly Selective Coulometric Method andEquipment for the Automated Determination ofPlutonium, ” in Analytical Chemistry in NuclearFuel Reprocessing, W. S. Lyon, Ed., Proc. 21st Conf.Anal. Chem. Energy Technol., Gatlinburg, Tennes-see, October 4-6, 1977 (Science Press, Princeton,1978), p. 151.

13

S. F. Marsh, J. E. Alarid, C. F. Hammond, M. J.McLeod, F. R. Roensch, and J. E. Rein, “Cation Ex-change of 53 Elements in Nitric Acid, ” Los AlamosScientific Laboratory report LA-7083 (February1978).

S. F. Marsh, J. E. Alarid, C. F. Hammond, M. J.McLeod, F. R. Roensch, and J. E. Rein, “Anion Ex-change of 58 Elements in Hydrobromic Acid and inHydriodic Acid,” LQSAlamos Scientific Laboratoryreport LA-7084 (February 1978).

J. E. Rein and G. R. Waterbury, “Preparation andChemical Characterization of Plutonium-239 Usedfor Half-Life Measurement,” Int. J. Appl. Radiat.Iaot., in press.

S. F. Marsh, R. ,M. Abernathy, R. J. Beckman, R.K. Zeigler, and J. E. Rein, “Plutonium-239 Half-Life Determined by Isotope Dilution Mass Spec-trometric Measurement of Grown-In Uranium-235,”Int. J. Appl. Radiat. Isot., in press.

S. F. Marsh, “Extraction-SpectrophotometricDetermination of Microgram Quantities of UraniumUsing Benzoyltrifluoroacetone, ” Anal. Chim. Acts.,in press.

REFERENCES

1. G. R. Waterbury, Comp., ‘Analytical Methodsfor Fissionable Materials in the Nuclear FuelCycle, June 1974 to June 1975,” Los AlamosScientific Laboratory report LA-6045-SR (Oc-tober 1975).

2. J. K. Kliwer, “Laser Evaporation and Elemen-tal Analysis, ” J. Appl. Phys. 44, No. 1, 490-492(1973).

3. L. Leibowitz and L. W. Mishler, “A Study ofAluminum-Water Reactions By Laser Heating, ”J, Nucl. Mater, 23, 173-182 (1967).

4, D. D. Jackson, D, J, Hodgkins, R. M, Hollen,and J. E. Rein, “Automated Spectrophotometerfor Plutonium and Uranium Determination, ”Los Alamos Scientific Laboratory report LA-6091 (February 1976).

14

5. G. R. Waterbury, Comp., ‘Analytical Methodsfor Fissionable Material Determinations in theNuclear Fuel Cycle, October 1, 1976—September 30, 1977,” Los Alamos ScientificLaboratory report LA-7013-PR (January 1978).

6. R. M. Hollen, D. D. Jackson, and J. E. Rein,“Evaluation of the LASL Automated Spec-trophotometer for Uranium Determination atSubmilligram Levels,” Los Alamos ScientificLaboratory report LA-6867 (July 1977).

7. D. D. Jackson, R. M. Hollen, S. F. Marsh, M. R.Ortiz, and J. E. Rein, “Determination of Sub-milligram Amounts of Uranium with the LASLAutomated Spectrophotometer, ” in AnalyticalChemktry in Nuclear Fuel Reprocessing, W. S.Lyon, Ed., Proc. 21st Conf. Anal. Chem. EnergyTechnol., Gatlinburg, Tennessee, October 4-6,1977 (Science Press, Princeton, 1978), p. 126.

8. G. R. Waterbury, Comp., “lbalytical Methodsfor Fissionable Materials in the Nuclear FuelCycle, July 1, 1975—September 30, 1976,” LosAlamos Scientific Laboratory report LA-6577-PR (December 1976).

9. D. D. Jackson, R. M. Hollen, F. R. Roensch,and J. E. Rein, “Highly Selective CoulometricMethod and Equipment for the AutomatedDetermination of Plutonium, ” in AnalyticalChemistty in Nuclear Fuel Reprocessing, W. S.Lyon, Ed., Proc. 21st Conf. Anal. Chem. EnergyTechnol., Gatlinburg, Tennessee, October 4-6,1977 (Science Press, Princeton, 1978), p. 151.

10. S. F. Marsh, J. E. Alarid, C. F. Hammond, M.J. McLeod, F. R. Roensch, and J. E. Rein, “Ca-tion Exchange of 53 Elements in Nitric Acid, ”Los Alamos Scientific Laboratory report LA-7083 (February 1978).

11. S. F. Marsh, J. E, Alarid, C, F. Hammond, M.J. McLeod, F. R. Roensch, and J. E, Rein,“Anion Exchange of 58 Elements inHydrobromic Acid and in Hydriodic Acid, ” LosAlamos Scientific Laboratory report LA-7084(February 1978).

12. R. L. Walker, R. E. Eby, C. A. Pritchard, and J.A. Carter, “Simultaneous Plutonium andUranium Isotopic Analysis from a Single ResinBead—A Simplified Chemical Technique forAssaying Spent Reactor Fuels,” Analyt. Lett.7(8&9), 563-574 (1974).

13. A. R. Eberle, M. W. Lerner, C. G. Goldbeck,and C. J. Rodden, “Titrimetric Determinationof Uranium in Product, Fuel, and ScrapMaterials after Ferrous Ion Reduction inPhosphoric Acid,” New Brunswick Laboratoryreport NBL 252 (July 1970).

14.J. E. Rein, G. M, Matlack, G. R. Waterbury, R.T. Phelps, and C. F. Metz, “Methods ofChemical Analysis for FBR Uranium-Plutonium Oxide Fuel and Source Materials, ”Los Alamos Scientiilc Laboratory report LA-4622 (March 1971).

15.J. E. Rein, G. L. Tietjen, R. K. Zeigler, and G.R. Waterbury, “Preparation of WorkingCalibration and Test Materials: Mixed Oxide, ”Los Alamos Scientific Laboratory report LA-7322 (NUREG/CR-0139) (September 1978).

16.J. L. Drummond and G. A. Welch, “ThePreparation and Properties of Some PlutoniumCompounds. VL Plutonium Oxide, ” J. Chem.SOC.4781-5 (1957).

18.J. E. Rein and G. R. Waterbury, “Preparationand Chemical Characterization of Plutonium-239 Used for Half-Life Measurement, ” Int. J.Appl. Radiat. Isot., in press.

19. S. F. Marsh, R. M. Abernathy, R. J. Beckman,R. K. Zeigler, and J. E. Rein, “Plutonium-239Half-Life Determined by Isotope Dilution MassSpectrometric Measurement of Grown-InUranium-235,” Int. J. Appl. Radiat. Isot., inpress.

20. A. H. Jaffey, H. Diamond, W. C. Bentley, D. G.Graczyk, and K. F. Flynn, “HaM-Life of ‘“Pu, ”Phys. ReV. C 18, No. 2, 969-973 (1978).

21. “American National Standard CalibrationTechniques for the Calorimetric Assay ofPlutonium-Bearing Solids Applied to NuclearMaterials Control, Appendix B,” AmericanNational Standards Institute, Inc., ANSIN15.22-1975 (June 1975).

22. C, E. Pietri, “The Stability of Plutonium Sul-fate Tetrahydrate, an Analytical Standard: ATen-Year Evaluation,” Talanta 18, 849-852(1971).

23. I. K. Kressin and G. R. Waterbury, “The Quan-titative Separation of Plutonium from VariousIons by Anion Exchange,” Anal. Chem. 34,1598-1601 (1962).

17.J. W. Dahlby, R. R. Geoffrion, and G. R. Water-bury, “The Sealed-Reflux Dissolution System, ”Los A)amos Scientific Laboratory report LA-5776 (January 1975).

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