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Radiochemistry in Nuclear Power Reactors Appendix E SELECTED RADIOCHEMICAL PROCEDURES Page No. E.1 Determination of Radioactive Iodine in Water E-2 E.2 Determination of Strontium-89/90 E-5 E.3 Determination of Iron-55 E-17 E.4 Determination of Nickel-63 E-23
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Radiochemistry in Nuclear Power Reactors E.1 DETERMINATION OF RADIOACTIVE IODINE IN WATER E.1.1 Principle Iodine is separated from the other radioactive species by extraction into carbon tetrachloride. Before this extraction is made, a complete interchange must be affected between the added iodine carrier and the tracer iodine present in the sample. The carrier iodide (I−) is oxidized to periodate (IO4−) in alkaline solution by NaOCl. The IO4− is reduced to I2 by hydroxylamine hydrochloride (NH2OH•HCl) and extracted into CCl4. The I2 is back-extracted by reduction to I− with NaHSO3. Iodide is then precipitated as silver iodide for chemical yield measurement and radioactivity counting. E.1.2 Reagents CCl4 (Note 1) Ethyl alcohol, 95% HNO3, concentrated Iodine carrier, 10.0 mg I−/mL (Note 2) NaOH, 5M NaOCl, 5% HN2OH HCl, 1M NaHSO3, 0.5 M AgNO3, 0.1 M E.1.3 Procedure In a 250 mL separatory funnel containing 100 mL water sample (Note 3), add 2 mL of I− carrier solution, 2 mL of NaOH, and 4 mL of NaOCl. Shake funnel for 2 minutes. Add 50 mL of CCl4, 4 mL of 1M NH2OH HCl and 3 mL of conc. HNO3. Shake the funnel for 2 minutes, and allow phases to separate.
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Radiochemistry in Nuclear Power Reactors Transfer CCl4 to a 125 mL separately funnel. Add 20 mL water containing a 1 mL conc. HNO3 and shake for 2 minutes. Allow phases to separate. Transfer CCl4 to a clean 125 mL separately funnel containing 20 mL H2O. Add, dropwise, 0.5 M NaHSO3. Shake until the purple color in CCl4 disappears. Allow phases to separate (Note 4). Transfer the aqueous phase to a 40 mL centrifuge cone. Add 0.5 mL conc. HNO3 and 2 mL of 0.1 M AgNO3. Stir and heat the solution in a hot water bath for ~5 minutes. Filter the AgI precipitate onto a tared No. 542 Whatman paper. Wash with water and alcohol. Dry the sample in an oven at 115°C for 15 minutes. Cool, weigh and mount for activity measurement. Follow the procedure described in Appendix C.1 for gamma spectrometric analysis of iodine activities. Notes: 1,1,1-trichloroethane or cyclohexane can be used in place of CCl4. Iodide carrier should be prepared monthly in slightly basic solution to prevent air oxidation. The sample size may vary, depending on the activity concentration in the sample. If 20 mL or less sample is used, the sample is diluted with appropriate volume of water. If further purification is desired, discard the organic phase. Add 20 mL of CCl4, 1 mL of conc. HNO3, and 2 mL of 1M NaNO2. Repeat the procedure starting at Step C.
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Radiochemistry in Nuclear Power Reactors E.1.4 References (1) “Standard Test Methods for Radioactive Iodine in Water”, D2334, ASTM Standards, Part 31. (2) L.E.Glendenin and R.P.Metcalf, “Radiochemical Studies of the Fission Products”, Book 3, p. 1625, National Nuclear Energy Series.
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Radiochemistry in Nuclear Power Reactors E.2 DETERMINATION OF STRONTIUM-89/90 E.2.1 Principle of Analysis Chemical separation of strontium from other fission and corrosion products involves precipitations of SrCO3 and Sr(NO3)2. The gross activities of purified Sr-89 and Sr-90 are first measured. Yttrium-90 is then allowed to grow into the strontium sample, and at a later time, the Y-90 activity is separated and measured. The Sr-90 activity is calculated from the Y-90 activity, and the Sr-89 activity is calculated from the difference between the total Sr-89 and Sr-90 activities measured and the calculated Sr-90 activity. A general scheme of analysis is shown below: Chemical separation for Sr-89 and Sr-90. Record time of separation, t1. Mount SrCO3 and count immediately. Hold SrCO3 for at least 10 days for Y-90 growth. Milk Y-90 from SrCO3 and record time of separation, t2. Mount Y2O3 and count Y-90 activity at t3. Recount Y2O3 for a 64.1 hr half-life decay to check purity of separation. Calculate Sr-90 activity from Y-90 activity. Calculate Sr-89 activity from total and Sr-90 activities. The following three procedures are described: Strontium separation Yttrium separation Preparation of counting efficiency curves for Sr-89, Sr-90 and Y-90.
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Radiochemistry in Nuclear Power Reactors E.2.2 Strotium Separation Reagents Sr carrier (10.0 mg/mL) Cs scavenger carrier (10 mg/mL) Co scavenger carrier (10 mg/mL) Mn scavenger carrier (10 mg/mL) Fe scavenger carrier (10 mg/mL) Ba scavenger carrier (10 mg/mL) La scavenger carrier (10 mg/mL) Conc. HNO3 Conc. NH4OH 3N or 6N HCl Sat. Na2CO3 Fuming HNO3 K2Cr2O7, 10% solution Ice bath Procedure Obtain the water sample directly or the leaching solution from cation membranes. Add 2.0 mL Sr carrier, and 4 drops each of Co, Cs, Mn, and Ba scavenger carrier to 100 mL sample in a 250 mL beaker. (Note: If the sample volume is less than 25 mL, use a 40 mL cone and omit the next step.) Add 5 mL of cone. HNO3 and boil down to ~10 mL. Transfer solution to a 40 mL cone with H2O. Add 2 mL 10% K2Cr2O7 and conc. NH4OH until solution is basic. Check with pH paper.
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Radiochemistry in Nuclear Power Reactors Centrifuge and discard ppt. Add sat. Na2CO3 to solution to ppt. SrCO3. Centrifuge and discard supernate. Wash SrCO3 with 20 mL H2O and centrifuge and discard supernate. Add 20 mL of fuming HNO3 and place in ice bath for 10 minutes. Centrifuge and discard fuming HNO3. Add 20 mL H2O to dissolve Sr(NO3)2 and add 6 drops of Fe scavenger carrier. Add conc. NH4OH to ppt. Fe(OH)3. Centrifuge and discard ppt. Add sat. Na2CO3 to the supernate to ppt. SrCO3. Repeat steps (g.) through (m.) and go to step (p.). Filter supernate through Whatman 41. Record time of separation. Add sat. Na2CO3 to filtrate to form SrCO3. Filter through Whatman 542 (tare) and wash with 10 mL of H2O and final rinse with 5 mL of acetone. Dry in oven 110°C for 15 minutes. Cool in desiccator for 10 minutes and weigh. Cover sample with 1/4 mil Mylar. Count the β activity in the sample immediately.
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Radiochemistry in Nuclear Power Reactors E.2.3 Separation of Yttrium-90 Reagents Y carrier (10.0 mg/mL) HNO3—concentrated HCl—concentrated and 6N HF—concentrated NH4OH—concentrated AgNO3–0.1M (NH4)2C2O4—saturated Methyl Alcohol H3BO3—saturated Procedure Allow the purified strontium sample to decay for ≥10 days. Pipet 2 mL Y carrier, 3 mL conc. HNO3, and 10 mL H2O into a 40 mL cone. With a scalpel, cut through the Mylar and around the Whatman 542 filter paper containing the purified strotium sample. Place Mylar, sample, and filter paper into the cone that contains the carrier and mix well. Add 10 drops of 0.1M AgNO3 and 1 mL conc. HCl and heat to boiling, Centrifuge and discard filter paper, Mylar, and ppt. Add 3 mL conc. HF to the solution and mix. Centrifuge and discard supernate. Wash YF3 ppt. with 10 mL H2O. Centrifuge and discard washing. (Note: Record separation time.)
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Radiochemistry in Nuclear Power Reactors Add 2 mL sat. H3BO3 and mix well. Add 2 mL conc. HNO3 and 10 mL H2O. Place in hot bath for 10 minutes. [Note: If solution appears turbid, centrifuge and discard sediment (AgCl).] Add 5 mL conc. NH4OH and mix well. Centrifuge and discard supernate. Wash Y(OH)3 with 10 mL H2O. Centrifuge and discard washing. Dissolve Y(OH)3 with 5mL 6N HCl and 15 mL H2O and place in hot bath for 5 minutes. Add 20 mL (NH4)2C2O4 mix and place in hot bath for 5 minutes. [Note: If a white ppt. does not form after addition of (NH4)2C2O4, add a few drops of conc. NH4OH and mix.] Chill in ice bath for 5 minutes. Filter onto a Whatman 542 and place in a porcelain crucible and ignite at 1000°C for 60 minutes. Cool to room temperature and grind the ppt. (Y2O3) to a fine powder with a stirring rod. With the aid of methyl alcohol, transfer the Y2O3 powder to a tared filter paper #542 Whatman. Oven dry at 110°C for 20 minutes. Cool in a desiccator for 10 minutes and weigh. Cover sample with 1/4 mil Mylar and count. Recount the sample in 1 to 2 weeks and check for a 64.1 hr half-life decay, checking purity of separation.
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Radiochemistry in Nuclear Power Reactors E.2.4 Preparation of Counting Efficiency (Self-Absorption) Curves Self-absorption Curve for Sr-89 Pipet 25.0 mL of Sr carrier and appropriate amount of Sr-89 standard into a 125 mL erlenmeyer flask that contains a magnetic stirring rod. Place erlenmeyer flask on a magnetic stirring plate and stir solution gently. Add conc. NH4OH until solution is just basic. Add sat. Na2CO3 to ppt. SrCO3. Pipet desired volumes of slurry into the tower of a Millipore glass filter holder that contains 10 mL H2O. (A minimum of 10 samples with varying amounts of slurry should be prepared.) Wash ppt. with 5 mL of H2O and rinse with 5 mL acetone. Oven dry at 110°C for 15 minutes. Cool in a desiccator for 10 minutes and weigh. Cover samples with 1/4 mil Mylar and count. Calculate the counting efficiency for each sample. Plot counting efficiency vs. sample weight, (see Figure E-1) Self-absorption Curve for Sr-90 Pipet 25.0 mL Sr carrier and appropriate amount of Sr-90 standard into a 40 mL centrifuge cone. Mix. Add 1 mL Y carrier and mix.
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Radiochemistry in Nuclear Power Reactors Add conc. NH4OH dropwise to ppt. Y(OH)3. Centrifuge and then add 1 drop of conc. NH4OH to supernate to ascertain completion of Y(OH)3. Decant the supernate to a clean cone and adjust the pH to less than 7 with conc. Repeat steps (b.) through (e.), then go to step (g.). Filter the supernate through Whatman 41 into a clean cone. Add sat. Na2CO3 to ppt. SrCO3. Centrifuge and discard the supernate. Wash ppt. with 20 mL H2O and centrifuge, discarding the washing. (Note: Record time for separation time for Sr-90.) Dissolve the SrCO3 in a minimum amount of 4N HNO3 and transfer the solution into a 125 mL erlenmeyer flask. Add H2O to make a total volume of 100 mL and place a magnetic stirring rod into the flask. Place the flask on a magnetic stirring plate and stir solution gently. Add conc. NH4OH until solution is just basic. Add sat. Na2CO3 to ppt. SrCO3. Using a transfer pipette and a syringe, pipet desired volume of slurry into the tower of a Millipore that contains about 10 mL of H2O. (A minimum of 10 samples with varying amounts of slurry should be prepared.)
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Radiochemistry in Nuclear Power Reactors E.3 DETERMINATION OF IRON-55 E.3.1 Principle of Analyses This procedure is to determine the Fe-55 content in the presence of Fe-59 in water or solid samples. Iron isotopes Fe-55 and Fe-59 are separated from fission and corrosion products by ion exchange and organic extraction. The organic phase is then transferred into a counting vial containing toluene base scintillator cocktail. The sample is counted with a liquid scintillation detector. E.3.2 Separation and Purification Procedures Reagents Fe carrier (10.0 mg/mL) Co, Cs, Mn, Cr hold-back carrier (~10 mg/mL) HCl—concentrated, IN, 6N, 9N NaOH—IN and 3N NH4OH—concentrated Anion resin—AG 1×10 50–100 mesh in chloride form Bis(2-ethylhexyl) Hydrogen Phosphate Toluene Buffer solution—pH 2.2 Dissolve 14.9 gm KCl in 1000 mL H2O, label as 0.2M KCl Dilute 16.5 mL of conc. HCl to 1000 mL of H2O and label as 0.2N HCl Mix 500 mL of 0.2M KCl with 78 mL of 0.2N HCl for buffer solution Analytical Ash-free filter pulp Isopropyl ether Liquid scintillation cocktail (POPOP solution)
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Radiochemistry in Nuclear Power Reactors Separation Procedure Pipet 250λ, of Fe carrier, add 4 drops each of Co, Cs, Mn, Cr, hold back carrier in a 1-L beaker containing 500 mL water sample. (Note: If the sample is a solution from solid, or filter paper dissolution, use 20 mL sample solution and add all carrier as specified above. Continue on step g.) Add 10 mL of conc. HCl to sample and mix well and heat to near boiling. Add conc. NH4OH until solution is basic to precipitate Fe(OH)3. Warm the solution and allow the precipitate to settle. Cool solution to room temperature, then carefully decant the clear solution as much as possible, or until about 30 mL slurry remaining. Carefully transfer the slurry to a 40 mL centrifuge tube. Rinse the beaker with 5 mL H2O and add the rinse to the centrifuge tube. Continue on step h. If a smaller size sample is used, add conc. NH4OH to precipitate Fe(OH)3. Centrifuge and discard the supernate. Wash the precipitate with 20 mL water containing a few drops of NH4OH. Centrifuge and discard the supernate. Add 6N HCl to dissolve the precipitate. Quantitatively transfer the dissolved Fe into a 50 mL flask. Use 6N HCl to complete the transfer to 50 mL volumetric flask. DO NOT USE ANY WATER.
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Radiochemistry in Nuclear Power Reactors Pipet 1 mL for Fe analysis by A.A. for 100% yield. After pipetting 1 mL for Fe analysis, add 1 drop of Co, Cs, Mn, Cr carrier directly into flask and mix well. Transfer the entire solution to a preconditioned anion column which has been rinsed with 6N HCl. After loading the column, rinse column with additional 15 mL 6N HCl. Upon completion of 6N HCl rinse, add 25 mL H2O. Continue to allow the effluent to drip into a waste beaker. CAREFULLY watch for the yellow effluent and collect only THIS effluent into a 40 mL centrifuge tube. Fe-Purification Dilute the solution to ~10 mL. Add conc. NH4OH to precipitate Fe(OH)3. Centrifuge and discard the supernate. Dissolve the precipitate in 10 mL of 9N HCl and extract the iron with 10 mL of isopropyl ether in a 50 mL separatory funnel. Separate the phase and discard the aqueous phase. Back extract with ~8 mL H2O and transfer the aqueous phase into a 10 mL volumetric flask. Add H2O to make up total volume and mix well. Pipet 1 mL for Fe analysis to determine chemical yield by A.A.
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Radiochemistry in Nuclear Power Reactors Pipet 5 mL to a centrifuge tube and add 5 mL Buffer solution. Add IN or 3N NaOH dropwise to adjust to pH 2. Check with pH paper. (Note: Adjusting to pH 2 is a critical step. This will insure 100% extraction into organic.) Add 5 mL of 50% bis(2-ethylhexyl)hydrogen-phosphate and SHAKE for 30 seconds. Transfer organic layer to a 12 mL conical centrifuge cone with the aid of a transfer pipet. Centrifuge for 2 minutes at medium rpm. Transfer the organic layer with a pipet to a counting vial that contains 10 mL liquid scintillation cocktail solution. Shake for 5 seconds and allow to stand for 12 hours before counting in a liquid scintillation counter. Using the calibrated counting efficiency to calculate the Fe-55 activity content (see below). Using the same sample, determine the Fe-59 activity content with a gamma-ray spectrometer. E.3.3 Standard Calibration and Radioactivity Measurement Prepare a standard calibration curve as follows: Pipet various known amounts (50λ to 5000λ) of Fe carrier to several culture tubes. Pipet 100λ of Fe-55 standard into each tube.
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Radiochemistry in Nuclear Power Reactors Pipet 5 mL of pH 2.2 buffer into each tube. Add 3N or 1N NaOH dropwise to adjust to pH 2. Check with pH paper. Add 5 mL of 50% bis(2-ethylhexyl)hydrogen phosphate and SHAKE for 30 seconds. Allow culture tube to stand for 5 minutes in rack for organic layer to separate. Transfer the organic layer (upper) to a 12 mL conical cone (use a transfer pipet) and centrifuge for 2 minutes at medium rpm. Transfer the organic layer to a counting vial containing 10 mL liquid scintillation cocktail. Shake well and store in a dark area for 12 hours before counting in a liquid scintillation detector with appropriate energy discrimination settings. (Note: The energy discrimination settings are determined by using pure Fe-55 and Fe-59 isotopes separately in the counting samples. The lower energy channel should include most of the Fe-55 counting but minimizing the interference from Fe-59 which is counted in the higher energy channel.) Calculate the Fe-55 counting efficiency from each standard sample and prepare a calibration curve of % eff. Fe-55 vs. external standard ratio (ESR). For the analytical samples count the sample in the predetermined energy channel. Obtain the count rate and the ESR from the calibration curve. The counting efficiency for the sample is estimated and the activity content in the sample is calculated.
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Radiochemistry in Nuclear Power Reactors E.3.4 Reference (1) S.E.Graber, et al, J. Lab. Clin. Med. G9, 170 (1967).
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Radiochemistry in Nuclear Power Reactors E.4 DETERMINATION OF NICKEL-63 E.4.1 Principle of Analyses Nickel-63 is separated from fission and corrosion products by anion ion-exchange resins and organic extractions. Nickel-63 is purified in chloroform as nickel dimethylglyoxime and back extracted with dilute HCl and then complexed with ammonium thiocyanate and precipitated with pyridine. Nickel precipitate is then dissolved in cocktail for counting with a liquid scintillation counter. E.4.2 Separation and Purification Reagants Ni carrier (10.0 mg/mL) Fe, Co, Cs, Mn hold-back carrier (~10 mg/mL) HCl—6N concentrated NaOH—1N NH4OH—concentrated Anion resin—AG 1×10 50–100 mesh chloride form Dimethylglyoxime—1% solution in Ethanol Liquid scintillation (POPOP solution) cocktail Toluene Chloroform Analytical filter paper pulp—Ash free Pyridine NH4SCN 1% solution+Pyridine 1% solution=rinse solution NH4SCN—20% solution HAC-1N Alconex—0.25%
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Radiochemistry in Nuclear Power Reactors Separation Procedure To 500 mL of water sampled in a 1-L beaker, add 500λ of Ni carrier, 4 drops each of Cs, Fe, Co and Mn hold-back carrier, and 3 mL conc. HCl. (Note: If the sample is a solution from filter dissolation, use only 20 mL sample in a 40 mL centrifuge tube. Add all the carriers as specified above and continue on step g.) Heat the solution to near boiling. Slowly add 100 mL of 1N NaOH. Stir and warm the solution for about 10 min. Chill sample in ice bath to room temperature. Allow the precipitate to settle and carefully decant the clear solution as much as possible, or until ~30 mL slurry remains in beaker. Carefully transfer the slurry to a 40 mL centrifuge tube. Use 5 mL 1N NaOH to rinse the beaker and add the rinse to the centrifuge tube. Continue on step h. If smaller size sample is used, add enough 6N NaOH to precipitate the Ni carrier. Stir and warm the solution for about 10 minutes. Centrifuge to separate the precipitate. Discard the supernate. Rinse the precipitate with 10 mL 1N NaOH. Centrifuge again and discard the supernate. Dissolve the precipitate with conc. HCl and quantitatively transfer the solution to a 50 mL volumetric flask using conc. HCl to complete the transfer. DO NOT USE ANY WATER.
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Radiochemistry in Nuclear Power Reactors Add 2 drops of Co and Mn carrier, make up to final 50 mL by adding conc. HCl. Prepare an anion exchange column and rinse with 25 mL of 6N HCl. Pipet 1 mL into a 50 mL flask for Atomic Absorption analysis. Determine 100% chemical yield for Ni. Load the remaining sample onto the resin column using conc. HCl for rinsing. Collect the effluent (~50 mL) from the column into a 250 mL beaker, Heat the solution to near boiling and reduce the volume to ~25 mL. Ni Purification To the solution obtained in step p. in separation procedure, slowly add conc. NH4OH until solution is just basic, using pH paper as indicator. Add 10 mL of 10% sodium citrate and allow solution to cool to room temperature and then transfer to a separatory funnel. Add 20 mL of 1% dimethylglyoxime and mix well. Add 10 mL of chloroform and shake well and allow the layers to separate and transfer the chloroform (lower layer) to another separatory funnel. Back extract Ni-63 by adding 10 mL 0.1N HCl and shake well. Transfer aqueous layer to a 100 mL beaker. Repeat steps a. through e., and continue on step g.
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Radiochemistry in Nuclear Power Reactors Transfer aqueous layer to a 25 mL volumetric flask. Fill up to the mark with 0.1N HCl. Mix well. Pipet 1 mL into a 50 mL volumetric flask for determining Ni chemical yield by atomic absorption analysis. Pipet 20 mL to a 40 mL centrifuge tube, add 1N NaOH or 1N HAc to adjust to pH 6–7 using pH paper as indicator. Add 10 mL of 20% solution NH4SCN and mix, then add 3 drops of alconex. Add 5 drops of pyridine and mix well. Allow to stand for 10 minutes, then centrifuge and discard supernate. Wash ppt. with 1% NH4SCN+1% Pyridine wash solution, centrifuge and discard supernate. Dissolve ppt. with 15 mL of liquid scintillation cocktail and transfer to a counting vial and store in darkness for 12 hours before counting in a liquid scintillation counter with predetermined energy discrimination setting. E.4.3 Standard Calibration and Radioactivity Measurement Prepare a series of samples containing a known amount of Ni-63 activity and variable amount (0.5, 1.0, 2.0 5.0, 10.0 mg) of Ni carrier in 0.1N HCl solution in a 25 mL volumetric flask. Process each standard sample starting from step i. through step m. in Ni Purification.
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Radiochemistry in Nuclear Power Reactors Obtain the counting rate, as well as external standard ratio (ESR) for each standard with an energy discriminator setting to include ≥80% of the counting. (Use the C-14 channel if the liquid scintillation counter has no variable energy discriminator.) Prepare a counting efficiency curve, i.e., efficiency vs. weight of Ni or efficiency vs. E.S.R. Determine the counting efficiency for a sample from either the determined Ni content in the sample or the measured E.S.R. from the counter. E.4.4 References (1) C.Yonizawa, et al, J. Radioanal. Chem., 78, 7 (1983).
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