1、Designation: C 1638 06Standard Guide for theDetermination of Iodine-129 In Uranium Oxide1This standard is issued under the fixed designation C 1638; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A numbe
2、r in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This method covers the determination of iodine-129(129I) in uranium oxide by gamma-ray spectrometry. Themethod could also be applicable to
3、the determination of129Iinaqueous matrices.1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and to determine theapplicability of regulat
4、ory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C 1402 Standard Guide for High-Resolution Gamma-RaySpectrometry of Soil SamplesD 1193 Specification for Reagent WaterD 3648 Standard Practices for the Measurement of Radio-activityD 3649 Standard Test Method for High-Resolution
5、Gamma-Ray Spectrometry in Water3. Summary of Practice3.1 An aliquot of uranium oxide is dissolved in dilute nitricacid and the iodine is selectively extracted via liquid-liquidextraction. The iodine is further purified by selective precipi-tation and counted by gamma-ray spectrometry.3.2 Gravimetric
6、 tracer recoveries using this method aretypically between 75 and 90 %.3.3 The minimum detectable activity (MDA) will vary withchemical yield, sample size, instrument background, countingtime and counting efficiency. For a sample size of 100 mg Uoxide, using a well shielded detector, a 1000 minute co
7、untingtime, and 32 % detector efficiency at 30 keV, a MDA of #0.74Bq/g (20 pCi/g) oxide was achieved.4. Significance and Use4.1 The determination of129I is not typically requested innuclear fuel specifications however it is commonly requestedfor disposal of the spent fuel, or for disposal of excess
8、uraniumfrom national weapon complexes. This practice can provideresults of sufficient quality for waste disposal repositories.5. Interferences5.1 Incomplete removal of uranium and its234Th/234mPadaughters could lead to elevated Compton background in thelow energy region of the gamma-ray spectrum, wh
9、ere the129Ix-rays are counted.5.2 Because the iodine yield monitor is added after theoxide dissolution, any loss of129I during the dissolution stepwill not be monitored and may lead to results that are biasedlow. To minimize any iodine loss, avoid prolonged heating ofthe sample and minimize the time
10、 the sample is in an acidicstate.6. Instrumentation6.1 Extended-range or low-energy gamma ray spectrometrysystem. See C 1402, D 3648 or D 3649 for a general descrip-tion of gamma-ray spectrometry systems. The system used tomeasure the low-energy x-rays from129I should have a thinwindow to allow the
11、efficient penetration and measurement ofthe low-energy x-rays.7. Terms and Definitions7.1 ROI: Region-of-Interest; the channels, or region, in thespectra in which the counts due to a specific radioisotopeappear on a functioning, calibrated gamma-ray spectrometrysystem.7.2 Reagent blank: reagent wate
12、r processed the same as thesamples; used in the determination of the minimum detectableactivity.1This guide is under the jurisdiction of ASTM Committee C26 on the NuclearFuel Cycle and is the direct responsibility of subcommittee C26.05 on Methods ofTest.Current edition approved Jan. 1, 2006. Publis
13、hed February 2006.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Har
14、bor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.8. Apparatus8.1 Plastic bottles, 30 and 60-ml, or separatory funnels8.2 Filter paper25-mm diameter, 0.45m pore size8.3 Vacuum filter apparatus8.4 pH paper with unit resolution9. Reagents and Materials9.1 Purity of ReagentsReagen
15、t grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available3.9.2 Purity of WaterUnless otherwise indicate
16、d, referencesto water shall be understood to mean Type I water as defined inSpecification D 1193.9.3 1M Hydroxylamine-hydrochloridecommerciallyavailable solution or dissolve 70 g of the powder in 500 mL ofwater, dilute to 1 litre final volume.9.4 Iodide carrier, 20 mg I-per millilitre as KI.9.5 Nitr
17、ic Acid, concentrated, ;16M9.6 0.1M Nitric AcidAdd ;6 mL of concentrated HNO3to 950 mL of water, dilute with water to a final volume of 1litre.9.7 8M Nitric AcidAdd 500 mL of concentrated HNO3to450 mL of water; dilute with water to a final volume of 1 litre.9.8 p-xylene.9.9 Palladium carrier;10 mg/m
18、L, dilute a commerciallyprepared solution to the correct concentration9.10 Sodium bisulfite, 0.1Mdissolve 10.4 g of powder in500 mL of water, dilute to a final volume of 1 litre9.11 Sodium Carbonate, 2Mdissolve 212 g of powder in500 mL of water, dilute to 1 litre final volume.9.12 Sodium Hydroxide,
19、4Mdilute a commercially pre-pared solution or dissolve 160 g of pellets in 700 mL of water,dilute to a final volume of 1 litre. This is a very exothermicreaction. The use of an ice bath can mitigate the magnitude ofthe exothermicity.9.13 Sodium Hypochlorite.10. Calibration and Standardization10.1 Th
20、e gamma-ray spectrometry system should be cali-brated for energy, resolution and efficiency according to themanufacturer instructions. The background counting rate forthe instrument should be measured at a frequency determinedby the user. See C 1402, D 3648 or D 3649 for additionalinformation. A typ
21、ical spectrum for129I is shown in Fig. 1.10.2 Confirm the concentration of the I-carrier by adding1.00 mL of the carrier solution to 15 mL of water. Add 1 mLof the 0.1M NaHSO3, mix, heat gently and then add 2 mL ofthe Pd+2carrier. Collect the precipitate (PdI2) on a tared 25-mmfilter paper. Dry and
22、reweigh the filter paper to confirm theexpected precipitate weight. Repeat this confirmation severaltimes to increase the precision of the determination.10.3 Prepare an efficiency curve for the 30 keV x-rayscomparing the relative efficiency versus weight of PdI2byprecipitating equal quantities of129
23、I with various weights ofPdI2. A typical curve for a Ge well detector is shown in Fig. 2;note that this curve shows the net count rate versus weight ofPdI2rather than calculated efficiency (the129I activity used toprepare this graph was 2.2 Bq (60 pCi).11. Procedure11.1 Weigh out no more than 100 mg
24、 of uranium oxide intoa small beaker.3“Reagent Chemicals, American Chemical Society Specifications,” AmericanChemical Society, Washington DC.FIG. 1 Low-Energy Photon Spectrum of I-129 on a Ge WellDetectorC163806211.2 Dissolve the oxide in about 20 mL of 0.1M HNO3.Heat gently, if required, to complet
25、e the dissolution.NOTE 1Avoid prolonged heating to minimize any iodine volatiliza-tion and possibly avoid heating altogether if only a small portion of thesample remains undissolved. Also, proceed directly to the next steps tominimize the time the sample is held under acidic conditions without thetr
26、acer present. Addition of the tracer prior to dissolution may not beappropriate since the sample iodine may not be in the same form andoxidation state as the tracer iodine.11.3 Add 1 mL of the 4M NaOH. Swirl the solution to mixand check the pH. The solution should be strongly basic.11.4 Add 1 mL of
27、the 2M NaCO3. Swirl to mix the solution11.5 Add 1.00 mL of the 20 mg/mL I-carrier. Swirl to mix.11.6 Add 1 mL of the NaHClO3solution to the beaker tooxidize the iodine to periodate (IO4-). Swirl to mix. Place thebeaker on a hotplate and heat the solution to just below boiling.Remove from the hotplat
28、e and cool to room temperature.CAUTION: The beaker and solution must be cool prior tothe next step.11.7 Carefully add 1 mL of the 8M HNO3. Swirl thesolution then check the pH. The solution should be stronglyacidic.11.8 Transfer the solution to a 60-mL plastic bottle orseparatory funnel. Rinse the be
29、aker a few times with smallportions of water and add to the bottle.11.9 Add 10 mL of p-xylene to the bottle.11.10 Add 3 mL of 1M NH2OH-HCl to the bottle to reducethe periodate to iodine (I2). Swirl to mix. The solution shouldbe red-purple in color at this point.11.11 Cap the bottle and shake for sev
30、eral minutes to extractthe iodine into the organic layer. Let the solution stand andallow the organic layer to separate from the aqueous layer.11.12 Remove the cap and draw off the top, organic layerwith a disposable pipette. Transfer the organic layer to a 30-mLplastic bottle or clean separatory fu
31、nnel.11.13 Add 15 mL of water to the organic in the 30-mLbottle. Add 1 mL of the 0.1M NaHSO3to the bottle to reducethe iodine to iodide (I-). Cap the bottle and shake for oneminute until the organic layer is colorless. Let the solutionstand and allow the organic layer to separate from the aqueouslay
32、er.11.14 Draw off the upper, organic layer and discard.11.15 Transfer the aqueous layer to a 100-mL beaker andgently warm the solution on a hotplate.11.16 Add 2 mL of the Pd+2carrier solution to the beaker.11.17 Allow the PdI2to precipitate and then filter thesolution through a tared 25-mm filter pa
33、per.11.18 Allow the filter paper to dry and then reweigh todetermine the chemical yield of the separation.11.19 Count the filter on an extended range or low-energygamma-ray spectrometry system for the length of time requiredto meet the requested detection limit. Set the ROI for129Itomonitor the 29-3
34、4 keV Xe K x rays.12. Calculation12.1 CALCULATION OF CHEMICAL YIELDY = mg PdI2recovered/mg PdI2expected based on calibra-tion (10.2)12.2 CALCULATION OF ACTIVITYAi5 Gi Bi! / Y * E * ABi* W!# (1)whereAi= activity of129I in Bq per gram U oxideGi= gross counts per second in the129I ROIBi= background cou
35、nts per second in the129I ROIY = yield calculated above expressed as a fractionE = detector efficiency for the 29-34 keV x-rays, ex-pressed as a fraction, based on the weight of the PdI2ABi= branching ratio for129I, expressed as a fractionW = weight of U oxide analyzed in gramsFIG. 2 Self-Adsorption
36、 of 30 keV X-ray versus Weight of PdI2H2OC1638063If the weight of uranium per gram of oxide is known thesample activity may be reported as Bq of129I per gram ofuranium by multiplying by the correct ratio.12.3 CALCULATION OF MINIMUM DETECTABLEAC-TIVITYMDAi5 4.65 * sB1 2.71! / E * Y * T * ABi* W! (2)w
37、hereMDAi= minimum detectable activity (Bq/g)sB= standard deviation of the reagent blank counts intime TT = sample counting time in seconds13. Keywords13.1 Gamma-ray spectrometry; liquid-liquid extraction;x-rayASTM International takes no position respecting the validity of any patent rights asserted
38、in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the
39、responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive ca
40、reful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM Internatio
41、nal, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).C1638064
