1、Designation: C 1475 05Standard Guide forDetermination of Neptunium-237 in Soil1This standard is issued under the fixed designation C 1475; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in paren
2、theses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers the determination of neptunium-237in soil by means of radiochemical separations and alphaspectrometry. This guide provides options
3、in the selection ofsample preparation, separation, and measurement. Althoughneptunium-237 is not a component of global fallout, it is aproduct of production reactors and spent fuel processing. Thisguide is designed for analysis of ten grams of soil previouslycollected and treated in accordance with
4、Practices C 998 andC 999. Larger-size samples of environmental soil may also beanalyzed, as long as the concentrations of interferences such asuranium and thorium are at or near environmental concentra-tions. Depending on the choice of a sample dissolution method,all chemical forms of neptunium may
5、not be completelysolubilized. This guide should allow the determination ofneptunium-237 concentrations from sub becquerel per gramlevels to applicable standards depending on count time, samplesize, detector efficiency, background, and tracer yield.1.2 This standard does not purport to address all of
6、 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 determine the applica-bility of regulatory limitations prior to use. Specific precau-tionary statements are given in Section 8.2. Refer
7、enced Documents2.1 ASTM Standards:2C 998 Practice for Sampling Surface Soil for RadionuclidesC 999 Practice for Soil Sample Preparation for the Deter-mination of RadionuclidesC 1000 Test Method for Radiochemical Determination ofUranium Isotopes in Soil by Alpha SpectrometryC 1001 Test Method for Rad
8、iochemical Determination ofPlutonium in Soil by Alpha SpectroscopyC 1163 Test Method for Mounting Actinides for AlphaSpectrometry Using Neodymium FluorideC 1284 Practice for Electrodeposition of the Actinides forAlpha SpectrometryC 1317 Practice for Dissolution of Silicate or Acid-Resistant Matrix S
9、amplesC 1342 Practice for Flux Fusion Sample DissolutionC 1387 Guide for Determination of Technetium-99 in SoilC 1412 Practice for Microwave Oven Dissolution of GlassContaining Radioactive and Mixed WastesD 1193 Specification for Reagent WaterD 1890 Test Method for Beta Particle Radioactivity ofWate
10、rD 3084 Practice for Alpha-Particle Spectrometry of WaterD 4962 Practice for NaI(TI) Gamma-Ray Spectrometry ofWaterIEEE/ASTM SI-10 Standard for the Use of the InternationalSystem of Units (SI): The Modern Metric System3. Summary of Guide3.1 This guide may be used to determine neptunium-237 insoil at
11、 potential release sites.Aneptunium-239 yield monitor isadded to the soil aliquot and the sample solubilized by one ofseveral methods, such as those described in Guide C 1387. Theneptunium is separated from the resulting solution using anextraction chromatography column. A valence adjustment isperfo
12、rmed prior to loading the sample onto the conditionedchromatography column. The sample is passed through thecolumn, which retains the neptunium in the +4 oxidation state.The column is washed to remove interferences and selectivelyeluted with dilute acid. The samples are prepared for measure-ment by
13、neodymium fluoride co-precipitation or electrodepo-sition, and the neptunium-237 content determined by alphaspectrometry. The neptunium-239 yield monitor is determinedby beta or gamma-ray counting.4. Significance and Use4.1 A soil sampling and analysis program provides a directmeans of determining t
14、he concentration and distribution ofradionuclides in soil. The presence and extent of neptunium-237 is of particular interest because it is one of the more mobiletransuranics in terms of migration and plant uptake. Since soilis an integrator and a reservoir on long-lived radionuclides, and1This guid
15、e is under the jurisdiction of ASTM Committee C26 on Nuclear FuelCycle and is the direct responsibility of Subcommittee C26.05 on Methods of Test.Current edition approved June 1, 2005. Published July 2005. Originally approvedin 2000. Last previous edition approved in 2000 as C 1475 00.2For reference
16、d 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 Harbor Drive, PO Box C700, West Con
17、shohocken, PA 19428-2959, United States.serves as an intermediary in several pathways of potentialimportance to humans, knowledge of the concentration ofneptunium-237 in soil is essential.5. Interferences5.1 Phosphates present in the sample matrix will interferewith the separation chemistry. Aluminu
18、m nitrate may be addedto the load solution to minimize this problem.5.2 High concentrations of uranium or thorium can overloadthe column, resulting in low recoveries of neptunium orspectral interferences. A preliminary separation may be re-quired to avoid spectral interference from uranium, see Test
19、Method C 1000. The presence of uranium-233 and uranium-234 could cause spectral interferences with the neptunium-237determination.6. Apparatus6.1 Apparatus for the sample dissolution and measurementare identified within the selected test method.6.2 Extraction Columns, with a bed volume of severalmil
20、lilitres for the extraction chromatography resin.37. Reagents7.1 Purity of ReagentsReagent 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 Soci
21、etywhere such specifications are available.4Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.7.2 Purity of WaterUnless otherwise indicated, referencesto water shall be underst
22、ood to mean reagent water as definedin Specification D 1193.7.3 Aluminum Nitrate Hydrate Al(NO3)39H2O.7.4 Aliphatic Quaternary Amine Extraction Chromatogra-phy Resin.37.5 Ferrous Sulfamate Fe(SO3NH2)2, 1.0 MDissolve38.8 g of sulfamic acid (NH2SO3H) and 11.6 g of iron powderin approximately 150 mL of
23、 water. Stir while heating untildissolved and then dilute to 200 mL with water. Prepare fresheach week or keep under a nitrogen blanket to minimizeoxidation.7.6 Hydrofluoric Acid (48 to 51 %)Concentrated hydrof-luoric acid (HF).7.7 Iron Powder.7.8 Nitric Acid (sp gr 1.42)Concentrated nitric acid(HNO
24、3).7.9 Nitric Acid, 3.0 MAdd 189 mL of concentrated nitricacid to 400 mL of water and dilute to 1.0 L with water and mix.7.10 2.5 M Nitric Acid-0.5 M Aluminum NitrateDissolve187.6 g of aluminum nitrate in about 500 mL of water, add 159mL of concentrated nitric acid, and dilute to 1.0 L.7.11 0.02 M N
25、itric Acid-0.02 M Hydrofluoric AcidAdd1.25 mL of concentrated nitric acid and 0.7 mL of concentratedhydrofluoric acid to 800 mL of water and dilute to 1.0 L withwater and mix.7.12 Radiometric Yield TracerNeptunium-239 is nor-mally used as a yield monitor in the determination ofneptunium-237. Where b
26、eta counting is used to determine theneptunium-239 yield, a relatively low amount of activity, forexample, 5 to 15 Bq, is typically required to obtain the desiredprecision with a 60-min count duration. Another option is theaddition of a known quantity of americium-243, in secularequilibrium with nep
27、tunium-239, directly to the sample. Thisapproach has the advantage of allowing the use of americium-243 solutions of NIST-traceable activity. Where gamma-raycounting is used to determine the neptunium-239 yield, a largeramount of activity, for example, 120 to 1200 Bq, may berequired to obtain the de
28、sired precision with a 10-min countduration dependent on the use of a NaI(TI) or HPGe detector.In this situation, it may be preferred to obtain the neptunium-239 from an americium-243 8cow.5This approach has theadvantage of conserving the americium-243 parent with theneptunium-239 activity being rep
29、lenished over time. However,it has the disadvantage that the neptunium-239 activity of themilked solution must be determined with high precision inorder to not adversely impact the precision of the sampleneptunium-237 activity determination.7.13 Sodium Nitrite (NaNO2).7.14 Sodium Nitrite, 3.0 MDisso
30、lve 2.1 g of sodiumnitrite in 10 mL of water. Prepare fresh daily.7.15 If prepacked columns are not available, prepare theresin by combining it with an equal volume of water, mix well,and allow to settle overnight. Decant the supernatant water.Prepare a column for each sample by pouring resin into e
31、achcolumn. Adjust the settled resin bed volume to approximately2 mL. Perpare only enough resin that is needed for use eachday.7.16 The use of dry-packed cartridges of the extractionchromatography resin in combination with a vacuum manifoldsystem has been found acceptable. When using vacuum-assisted
32、flow, it is essential to ensure that flow rates do notexceed 1 mL/min for load solutions and strip solutions, and 2mL/min for the rinse solutions. Alternately, follow the manu-facturers recommendations.8. Precautions8.1 Refer to the laboratorys chemical hygiene plan andother applicable guidance for
33、handling chemical and radioac-tive materials and for the management of radioactive, mixed,and hazardous waste.3Prepacked columns of TEVA Resin from Eichrom Technologies, Inc., Darien,IL, have been found to be satisfactory for this purpose.4Reagent Chemicals, American Chemical Society Specifications,
34、 AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc.
35、 (USPC), Rockville,MD.5Information on the generation and use of americium-243 cows to obtainneptunium-239 can be obtained from: Garraway, J., and Wilson, P. D., “Preparationof Np-239 by Separation from the Parent Am-243,” Journal of the Less-CommonMetals, 91, 1983, L13-L16, and Bubernak, J., Lew, M.
36、 S., and Matlack, G. M., “IonExchange Extraction, Separation and Radiochemical Determination of Neptunium-237 in Plutonium-238,” Analytica Chemica Acta, 48, 1969, pp. 233-241.C14750528.2 Hydrofluoric acid is a highly corrosive acid that canseverely burn skin, eyes, and mucous membranes. Hydrofluo-ri
37、c acid is similar to other acids in that the initial extent of aburn depends on the concentration, the temperature, and theduration of contact with the acid. Hydrofluoric acid differsfrom other acids because the fluoride ion readily penetrates theskin, causing destruction of deep tissue layers. Unli
38、ke otheracids that are rapidly neutralized, hydrofluoric acid reactionswith tissue may continue for days if left untreated. Due to theserious consequences of hydrofluoric acid burns, prevention ofexposure or injury of personnel is the primary goal. Utilizationof appropriate laboratory controls (hood
39、s) and wearing ad-equate personal protective equipment to protect from skin andeye contact is essential.9. Sampling9.1 Collect the sample in accordance with Practice C 998.9.2 Prepare the sample for analysis in accordance withPractice C 999.10. Sample Solubilization10.1 Weigh 10.00 g of dried and pr
40、epared soil and addneptunium-239 yield monitor in either a separated form or insecular equilibrium with americium-243. As indicated in 7.12,either beta counting using Test Method D 1890 or gamma-rayspectrometry using Practice D 4962 may be utilized for count-ing the neptunium-239 yield monitor. The
41、amount ofneptunium-239 yield monitor activity utilized is dependent onthe selected counting technique, the efficiency of the countingtechnique, and the desired counting duration. Obtaining ap-proximately 10 000 net counts from neptunium-239 by what-ever counting technique is used will produce a Pois
42、soncounting uncertainty of about 1 % at one standard deviation.Given the short half-life of neptunium-239, delay in itscounting will reduce the number of counts obtained withresulting increase in counting uncertainty.10.2 A number of methods are available to solubilize soilsamples to prepare them fo
43、r radiochemical analysis. Threefrequently used techniques are acid leaching, fusion, andmicrowave digestion. Leaching procedures are described inTest Methods C 1000 and C 1001. A general overview of allthree methods is provided in Guide C 1387 along with refer-ences to detailed procedures. Other met
44、hods include proce-dures for dissolution of silicates or acid-resistant matrixsamples in Practice C 1317, dissolution of solid samples byfusion in Practice C 1342, and the microwave dissolution ofglass in Practice C 1412. The choice of specific dissolutionmethod is left to the laboratory conducting
45、this analysis.11. Procedure11.1 Prepare any blanks, spikes, duplicates, or othersamples required by the laboratory protocols as part of thisanalysis in accordance with 10.2.11.2 All undigested solids should be removed by filtrationor centrifugation prior to performing this purification proce-dure. E
46、vaporate the samples to near dryness on a hot plate setat 110C.11.3 Remove the sample beakers from the hot plate andallow them to cool to room temperature.11.4 Add 5 mL of 2.5 M HNO3-0.5 M Al(NO3)3to eachbeaker and swirl to dissolve the residue.11.5 Add 0.4 mLof 1.0 M ferrous sulfamate solution to e
47、achbeaker.11.6 Add 0.5 mL of 3.0 M sodium nitrite to each samplebeaker.611.7 Allow the samples to sit at room temperature for 30 to40 min. The sample beakers should be swirled occasionally tofacilitate the reaction.711.8 During the 30-min incubation period, prepare theextraction chromatography colum
48、ns.11.9 For prepackaged columns, break off the tip and allowthe water to drip through into an appropriate waste container.11.10 For either column type, condition the columns byadding 5 mL of 3.0 M nitric acid. Collect the column wash aswaste.11.11 After the samples have reacted for 30 to 40 min,7loa
49、dthe samples on the columns using disposable transfer pipettes.Collect the effluent as waste.11.12 Rinse the sample beaker with 5 mL of 3.0 M nitricacid, pass this rinse through the column, and collect the rinseas waste.11.13 Repeat 11.12.11.14 Elute the neptunium by passing 15 mL of 0.02 MHNO3-0.02 M HF through each column. Collect the columnstrip solutions in clean, labeled teflon containers.11.15 Prepare the samples for alpha spectrometry by eitherco-precipitating with neodymium fluoride in accordance withTest Method C 1163 or by electrodeposition in accordance w
