1、Designation: C 791 04Standard Test Methods forChemical, Mass Spectrometric, and SpectrochemicalAnalysis of Nuclear-Grade Boron Carbide1This standard is issued under the fixed designation C 791; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、 revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover procedures for the chemical,mass spectrometric, and spectrochemical a
3、nalysis of nuclear-grade boron carbide powder and pellets to determine compli-ance with specifications.1.2 The analytical procedures appear in the following order:SectionsTotal Carbon by Combustion and Gravimetry 7-17Total Boron by Titrimetry 18-28Isotopic Composition by Mass Spectrometry 29-38Chlor
4、ide and Fluoride Separation by Pyrohydrolysis 39-45Chloride by Constant-Current Coulometry 46-54Fluoride by Ion-Selective Electrode 55-63Water by Constant-Voltage Coulometry 64-72Impurities by Spectrochemical Analysis 73-81Soluble Boron by Titrimetry 82-95Soluble Carbon by a Manometric Measurement 9
5、6-105Metallic Impurities by a Direct Reader SpectrometricMethod106-1142. Referenced Documents2.1 ASTM Standards:2C 750 Specification for Nuclear-Grade Boron Carbide Pow-derC 751 Specification for Nuclear-Grade Boron Carbide Pel-letsD 1193 Specification for Reagent WaterE 115 Practice for Photographi
6、c Processing in OpticalEmission Spectrographic AnalysisE 116 Practice for Photographic Photometry in Spectro-chemical AnalysisE 130 Practice for Designation of Shapes and Sizes ofGraphite Electrodes3. Significance and Use3.1 Boron carbide is used as a control material in nuclearreactors. In order to
7、 be suitable for this purpose, the materialmust meet certain criteria for assay, isotopic composition, andimpurity content. These methods are designed to show whetheror not a given material meets the specifications for these itemsas described in Specifications C 750 and C 751.3.1.1 An assay is perfo
8、rmed to determine whether thematerial has the specified boron content.3.1.2 Determination of the isotopic content of the boron ismade to establish whether the content is in compliance with thepurchasers specifications.3.1.3 Impurity content is determined to ensure that themaximum concentration limit
9、 of certain impurity elements isnot exceeded.4. Reagents4.1 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 Society,w
10、here such specifications are available.3Other 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.4.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood
11、to mean reagent water conformingto Specification D 1193.5. Safety Precautions5.1 Many laboratories have established safety regulationsgoverning the use of hazardous chemicals and equipment. Theusers of these methods should be familiar with such safetypractices.1These test methods are under the juris
12、diction of ASTM Committee C-26 onNuclear Fuel Cycle and are the direct responsibility of Subcommittee C26.03 onNeutron Absorber Materials Specifications.Current edition approved June 1, 2004. Published July 2004. Originally approvedin 1975. Last previous edition approved in 2000 as C 791 83(2000)2Fo
13、r 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.3“Reagent Chemicals, American Chemical Society Specifications,”
14、Am. Chemi-cal Soc., Washington, D.C. For suggestions on the testing of reagents not listed bythe American Chemical Society, see “Reagent Chemicals and Standards,” by JosephRosin, D. Van Nostrand Co., Inc., New York, N.Y., and the “United StatesPharmacopeia.”1Copyright ASTM International, 100 Barr Ha
15、rbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6. Sampling6.1 Criteria for sampling this material are given in Specifi-cations C 750 and C 751.TOTAL CARBON BY COMBUSTION ANDGRAVIMETRY7. Scope7.1 This method covers the determination of total carbon innuclear-grade, boron car
16、bide in either powder or pellet form.8. Summary of Test Method8.1 The sample mixed with a flux material is burned in anoxygen atmosphere at a temperature not lower than 1400C.The carbon dioxide product is passed through a gas-treatmenttrain to ensure that any carbon monoxide formed is convertedto ca
17、rbon dioxide and to remove dust, sulfur dioxide, andmoisture. The carbon dioxide is absorbed and weighed (1,2).49. Interferences9.1 At the specification limits usually established fornuclear-grade boron carbon, interferences are insignificant.10. Apparatus10.1 Analytical Balance, capable of weighing
18、 to 6 0.1 mg.10.2 Crucible, zircon ceramic.510.3 Crucible Covers, porous, ceramic.610.4 Mortar, diamond (Plattner), or boron carbide mortar.10.5 Combustion SystemThe letters in parentheses referto the components shown in Fig. 1.10.5.1 Induction Furnace (A)7Caution: Contact with thehigh-frequency ind
19、uction coil will produce severe electricalshock and may cause burns.10.5.2 Combustion Tube (B),8fused silica.10.5.3 Dust Trap (C).910.5.4 Catalyst Furnace (D).1010.5.5 Drying Tubes11The first tube (E1) is filled withmagnesium perchlorate and the second tube (E2) is filled withanhydrous calcium sulfa
20、te.12These tubes prevent water re-leased from the sample from entering the absorption bulb.10.5.6 Sulfur Trap (F).1310.6 Gravimetric SystemThe letters in parentheses referto components shown in Fig. 2.10.6.1 Nesbitt Absorption Bulb (A),14may be modified with12/5 socket joints on both the entrance an
21、d exit port. The bulbis filled as shown in Fig. 2.10.6.2 Drying Tube (B),12filled with magnesium perchlo-rate, anhydrous calcium sulfate, and sodium hydrate-asbestos15to prevent any back-diffusion of water and carbon dioxide intothe absorption bulb.10.6.3 Flowmeter (C)16The total system has two flow
22、me-ters, one located before the furnace (Fig. 3) and one after theabsorption bulb (Fig. 2). This arrangement helps to detect leaksin the system.10.7 Oxygen Purification SystemThe letters in parenthe-ses refer to the components shown in Fig. 3.10.7.1 Gas Regulator (A), for oxygen.10.7.2 Drying Tubes1
23、1The three tubes are filled as fol-lows: the first (B1) with magnesium perchlorate to dry theoxygen; the second (B2) with anhydrous calcium sulfate toindicate when trap B1is spent; the third tube (B3) with sodiumhydrate-asbestos to remove carbon dioxide.10.7.3 Gas Flow-Regulating Valve (C).1710.7.4
24、Flowmeter (D).1610.8 Sieve, No. 100 (150-m), U.S. Standard Sieve Series,3-in. diameter, brass or stainless steel.11. Reagents11.1 Calcium Sulfate, Anhydrous,12indicating.11.2 Copper, granules, 30 mesh.11.3 Copper, rings.1811.4 Cupric Oxide, reagent grade, used in the catalystfurnace (Fig. 1) to assu
25、re that any carbon monoxide formedduring combustion is converted to carbon dioxide.11.5 Iron, chips.1911.6 Magnesium Perchlorate, anhydrous.11.7 Manganese Dioxide.2011.8 Oxygen, ultra high purity grade or equivalent.2111.9 Sodium Hydrate-Asbestos,158 to 20 mesh.11.10 Tin, Granular.2212. Precautions1
26、2.1 Care should be taken to avoid carbon contamination ofreagents and laboratory equipment. Prior to making the initialanalysis, condition the furnace tube and absorption bulb bytaking a sample from 15.1-15.13 without making any measure-ments (omit 15.2, for example).13. Sample Preparation13.1 Crush
27、 a pellet with a mortar. Important: when using thediamond (Plattner) mortar, crush with a few, light hammerblows.NOTE 1Do not crush and grind the boron carbide extensively in thediamond mortar because significant iron contamination can occur, whichwill require an iron correction in the analysis.4The
28、 boldface numbers in parentheses refer to the list of references appended tothese methods.5Leco No. 528035 or equivalent.6Leco No. 528042 or equivalent.7Leco No. 521000 or equivalent.8Leco No. 550122 or equivalent.9Leco No. 501010 or equivalent.10Leco No. 507000 or equivalent.11Kimble No. 46010 or e
29、quivalent.12Drierite has been found satisfactory for this purpose.13Leco No. 503033 or equivalent.14Kimble No. 16010 or equivalent.15Ascarite has been found satisfactory for this purpose.16Manostat No. 1044B or equivalent.17Matheson No. 32 or equivalent.18Leco No. 550184 or equivalent.19Leco No. 501
30、077 or equivalent.20Leco No. 501060 or equivalent.21Matheson Gas Data Book, The Matheson Co. Inc., East Rutherford, N. J.,Fourth Edition, 1966.22Leco No. 501-076 or equivalent.C79104213.2 Pass the crushed sample through a metal No. 100 sieve.13.3 Repeat 13.1 and 13.2 until the whole pellet has passe
31、dthrough the sieve.13.4 Thoroughly mix the sieved sample.14. Blank14.1 A blank should be determined at least once in each 8-hshift in which total carbon analyses are made. The long-termaverage blank less than 1.5 % of the long-term average amountof carbon dioxide weighed in the analyses. If any indi
32、vidualblank varies from the long-term average by more than 6 20 %,investigate and correct the cause before continuing the analysisof samples. Use the long-term average blank in calculating theconcentration of carbon in samples.15. Procedure15.1 Add2goftin, 3 copper rings (m1.8 g), and 1.2 g ofcopper
33、 granules (30 mesh) to a crucible.NOTE 2To determine a blank, perform 15.1-15.15, omitting 15.2 and15.3.NOTE 3Prefiring of the crucibles is recommended to minimize blanks.NOTE 4These quantities of flux and coupler, including the3gofironchips added in 15.4, have been found satisfactory. Since furnace
34、s mayhave different power outputs and coupling characteristics, the quantities offlux and coupler and iron chips required may differ among furnaces.15.2 Weigh the crucible and its contents to 6 0.1 mg.15.3 Add 200 mg of sample in powder form to the weighedcrucible and reweigh to 6 0.1 mg.NOTE 5If a
35、sample is in pellet form, crush to a powder using theprocedure given in Section 13.15.4 Cover the sample with3gofiron chips.15.5 Cover the crucible with a porous ceramic cover.15.6 Load the crucible into the induction furnace.15.7 Purge the crucible and its contents with oxygen for 2min.NOTE 6The fl
36、ow rate of the gas should be about 0.5/min.15.8 Weigh the closed absorption bulb, using the weighingtechnique given in 15.16.NOTE 7Before taking the initial weight of the absorption bulb,condition it by purging with oxygen for1hat0.5/min.NOTE 8ImportantAfter obtaining the initial weight of the absor
37、p-tion bulb, do not touch it with the hands until all analyses have beencompleted. Lintless nylon gloves or their equivalent should be used tohandle the absorption bulb.15.9 Place the absorption bulb into position in the appara-tus.NOTE 9Use dry (no grease) ball and socket joints. Greased joints add
38、to the problem of reproducing weighings.15.10 Open the absorption bulb to the system and readjustthe oxygen flow to 0.5/min, if necessary.15.11 Turn on the induction furnace.NOTE 10The induction furnace should be preset at its highest gridcurrent setting so that the maximum temperature can be obtain
39、ed. Followthe manufacturers recommended procedure for operating the furnace.15.12 Burn the sample.NOTE 11If the combustion is incomplete after 8 min by visualinspection, investigate the flux and coupler conditions to determineconditions that will give complete combustion.15.13 Turn off the furnace a
40、nd wait an additional 22 min,allowing the oxygen to continue flowing through the entiresystem.15.14 Close the absorption bulb and remove it from theapparatus.15.15 Weigh the bulb using exactly the same technique usedin 15.16.15.16 Weighing Absorption Bulb:15.16.1 Wipe the closed absorption bulb thor
41、oughly andevenly with a moist chamois, being careful not to touch thebulb with the hands.NOTE 12Wiping the absorption bulb with a moist chamois minimizesthe adverse effects on weighing produced by static charges.15.16.2 Place the bulb on the balance pan with the balancedoor open.NOTE 13If a single-p
42、an balance with two doors is used, open bothdoors.15.16.3 Wait 3 min and close the door.NOTE 14Leaving the balance door open decreases the amount of timerequired for the absorption bulb to come to equilibrium after it has beenwiped with the moist chamois. The length of time required to reachequilibr
43、ium depends upon the relative humidity in the laboratory.15.16.4 Weigh the bulb to 6 0.1 mg.15.16.5 Repeat 15.16.1-15.16.4 until constant weight(6 0.1 mg) is obtained.16. Calculation16.1 Calculate the grams of carbon, C, weighed as follows:C 5 W22 W1!s2 W22 W1!b#0.2729! (1)where:W2= weight of absorp
44、tion bulb after combustion(15.15),W1= weight of absorption bulb before combus-tion (15.8),(W2W1)s= weight of CO2from sample, g, and(W2W1)b= blank measurement.16.2 Calculate the weight percent of carbon, Ca,inthesample as follows:Ca5 C/S22 S1!# 3 100 (2)where:C = amount of carbon weighed from the sam
45、ple, g,S2= weight of crucible plus sample (15.3), g, andS1= weight of crucible (15.2), g.17. Precision and Bias (3)NOTE 15Please see Ref (4) for all precision and bias statements,except those denoted by Ref (5) .17.1 PrecisionThe standard deviation is 0.14 mass %.17.2 BiasNo bias can be established
46、because no materialtraceable to a national standards base is available.C791043TOTAL BORON BY TITRIMETRY18. Scope18.1 This method covers the determination of total boron insamples of boron carbide powder and pellets. The recom-mended amount of boron for each titration is 100 6 10 mg.19. Summary of Me
47、thod19.1 Powdered boron carbide is mixed with sodium carbon-ate and this mixture is fused to decompose the boron carbide.The melt is dissolved in water, filtered to remove the insolubleresidue, acidified, and heated to remove carbon dioxide. Theboron as boric acid is titrated with standardized sodiu
48、mhydroxide solution, using the mannitoboric acid procedure(5,6,7).20. Interferences20.1 Metals that form hydrous oxides may distort the endpoint of the titration.21. Apparatus21.1 Balance, analytical, with a sensitivity of at least 0.05mg.21.2 Beakers, 400 and 600-mL, low-boron glass.21.3 Burners, b
49、unsen and Meker (alternative to mufflefurnace).21.4 Combination Electrode, glass-calomel.21.5 Filter Paper, open-textured, very rapid filtering, forcoarse and gelatinous precipitates.21.6 Muffle Furnace, capable of maintaining a temperatureof at least 1000C.21.7 pH Meter.21.8 Platinum Crucible, 30-mL, standard form with close-fitting cover.21.9 Polyethylene Funnel.21.10 Recording Titrator, capable of a precision of titrationof 100 ng of boron of at least 0.15 %.21.11 Temperature Programmer, used with muffle furnace(optional).22. Reage
