RADIOLOGICAL CHARACTERIZATION Laboratory Procedures

Transcription

1 RADIOLOGICAL CHARACTERIZATION Laboratory Procedures LORNA JEAN H. PALAD Health Physics Research Unit Philippine Nuclear Research Institute Commonwealth Avenue, Quezon city Philippines 3-7 December 2007 PURPOSE To measure activity concentration of materials taken from a shutdown nuclear research reactor To comply with regulatory requirements for clearance of materials for unrestricted or restricted reuse

2 RADIONUCLIDE INVENTORY. Neutron activated materials Located in the reactor structure and have been irradiated by neutrons Major activation products 3 H, 4 C, 22 Na, 36 Cl, 39 Ar, 4 Ca, 54 Mn, 55 Fe, 59 Ni, 63 Ni, 60 Co, 65 Zn, 93 Mo, 93 Zr, 94 Nb, 08m Ag, 0m Ag, 25 Sb, 33 Ba, 34 Cs, 52 Eu, 54 Eu, 55 Eu, 66m Ho 2. Contaminated Materials typically found as surface contamination in reactor systems where fuel failure has occurred, on fuel handling systems, and in primary heat transport systems of any reactor Major fission products 90 Sr, 99 Tc, 06 Ru, 29 I, 37 Cs, 44 Ce Major actinides Pu, 239 Pu, 24 Pu, 24 Am, 242 Cm, 244 Cm, 232 U, 233 U, 234 U, 235 U, 236 U, 238 U 2

3 MATERIALS TO BE SAMPLED Material samples -concrete, steel, resins, wood, tiles, paint chips, foam - pipes, sludge, pool water, etc Environmental samples - soil/sediment, grass, water Biological -urine, excrete Field Sample Preparation and Preservation Sample Receipt and Inspection Laboratory Sample Preparation Fig. Analytical Process Sample Dissolution Chemical Separation of Radionuclide of Concern Preparation of Samples for Instrument Measurement Instrument Measurement Data Reduction and Reporting 3

4 Field Sampling Sampling design should be carefully planned Sampling is the source of biggest contribution to error in analysis Sampling Concentration, Separation, Isolation, etc. Steps Sample Preparation Measurement Scwedt, 997 Figure 2. Degree of error in laboratory sample preparation relative to other activities 4

5 Sample Receipt and Inspection Sample Receipt -receive in designated areas -Check accompanying documents -Conduct radiological survey Sample Inspection -Check physical integrity of package and container -Confirm sample identity -Confirm field preservation, if any Laboratory Sample Tracking -Sample log-in -Sample tracking during analysis -Storage of sample Detection Methods, MDAs and Release Criteria for Radionuclides Isotope H-3 Half-life.2E+0 Emission Detection Methods Liquid Scintillation MDA, Bq/g 0 Clearance Level, Bq/g 00 C-4 5.7E+03 Liquid Scintillation Cl E+05 Liquid Scintillation Ca-4.0E+05 EC Liquid Scintillation ( to 0) Mn E-0 EC, γ Fe E+00 EC, X Liquid Scintillation or X-ray spectrometry 0 Co E+00, γ 0. Ni E+04 EC, X X-ray spectrometry 0 00 Ce E-0, γ Ni-63.0E+02 Liquid Scintillation 00 Cs-34 2.E+00, γ 0. Cs E+0, γ 0. 5

6 Isotope Half-life Emission Detection Methods MDA, Bq/g Clearance Level, Bq/g I-29.6E+07 ICPMS (or X ray spectrometry) Sr E+0 Beta counting or Liquid scintillation Zr-93.5E+06 ICPMS 0. Nb-93m.6E+0 IT, X X ray spectrometry or liquid scintillation 0 Nb E+04, γ (or ICPMS) (7) 0. Mo E+03 EC,X X ray spectrometry or liquid scintillation 0 0 Tc-99 2.E+05 ICPMS 0.6 Ru-06.0E+00, γ Ag08m.3E+02 EC, γ Ag-0m 7.0E-0, γ Sb E+00, γ Ba-33.E+0 EC, X, γ Isotope Half-life Emission Detection Methods MDA, Bq/g Clearance Level, Bq/g Eu-52.3E+0 EC,,X, γ 0. Eu E+00,X, γ 0. Eu E+00,X, γ Ho-66m.2E+03,X, γ U E+05 α. X Alpha spectrometry 0.02 U E+08 α,, γ ICPMS U E+09 α ICPMS Pu E+0 α. X Alpha spectrometry 0.02 Pu E+04 α Alpha spectrometry Pu-24.4E+0 Liquid scintillation Am E+02 α. X, γ Alpha spectrometry 0.02 Cm E+0 α. X Alpha spectrometry 0.02 Cm-244.8E+0 α. X Alpha spectrometry

7 Gamma Spectrometry Nondestructive analysis of gamma emitting radionuclides Requires minimum sample preparation Measure gamma radiation using scintillation detectors (NaI (Tl)) crystals and semiconductor detectors (High purity germanium detectors) I. Sample Preparation. Liquid Samples Evaporation Adsorption with AMP (Cs)/Precipitation with MnO2 (other metals except Cr) Ion-exchange resin 2. Solid Samples Dry, grind, sieve, mix to homogenize, get sub sample 3. Air particulate filters,swipe/smear Samples No pretreatment Leach with dilute HNO3 or 0.05M EDTA 7

8 II. Standard Calibration III. Spectrometer Calibration. Energy Calibration 2. Efficiency Calibration 3. Quality Control Check IV. Sample Measurement. Count a blank sample 2. Determine minimum detectable activity (MDA) 3. Count sample V. Statistical Treatment of Data. Calculate Activity including correction factors 2. Calculate total uncertainty Alpha Spectrometry Analysis of alpha emitting radionuclides Requires radiochemical separation Use of Si semiconductor detectors 8

9 I. Sample Treatment. Liquid Samples Acidify and filter May reduce volume by evaporation or ion exchange 2. Solid Samples Drying, grinding, sieving, homogenize May reduce volume by ashing Sample decomposed with concentrated acids, e.g. HCl, HNO 3, HF; H 2 O 2 or alkali fusion with K 2 CO 3 Sample can be leached with dilute nitric acids or complexing agents 3. Air Particulate or Swipe/Smear Samples Cellulose and membrane filters can be dissolved in mineral acids Glass-fiber filters can be leached with dilute acids or chelating agents I. Preconcentration II. III. Precipitation Chemical Separation Anion exchange Source Preparation Electrodeposition Precipitation with cerium or lanthanum IV. Counting 9

10 Plutonium Analysis by Alpha Spectrometry Sample Filtration HCl Residue Solution Fe carrier Pu tracer NH 4 OH Centrifugation (Fe(OH) 3 Precipitate Supernatant Supernatant HNO3 HCl HI-HCl Anion exchange U, Fe Th Pu Electrodeposition α spectrometry Liquid Scintillation Counting Gross alpha/beta analysis of samples Analysis of beta emitters Analysis of alpha emitters May require radiochemical separation 0

11 I. Sample Preparation. Liquid Samples Distillation/electrolytic enrichment ( 3 H) Oxidation/CO 2 trapping ( 4 C) Reduce volume by evaporation, ion exchange,precipitation 2. Solid Samples Dissolution with concentrated mineral acids (for activated and geogenic samples) Leaching with dilute mineral acids (for surface contaminated samples Reduce volume by ashing at high tempeatures (except volatile radionuclides, e.g. 29 I, 99 Tc 3. Air Particulate/Swipe/Smear Samples II. Cellulose and membrane filters can be dissolved in concentrated mineral acids Glass fiber filters can be leached with dilute mineral acids or chelating agents Filter paper can be placed directly in LSC vial with addition of liquid scintillant Setting of Measurement Conditions for Radionuclide Determination of Figure of Merit (FOM) III. Drawing of Quench Correction Curve Preparation of quench standards Draw quench correction curve Efficiency determination

12 IV. Counting of Sample V. Calculation of Activity Calculate Average, X + 3σ Correct activity using decay correction factor Tritium Analysis by Liquid Scintillation Counting Distillation Method Sample (00ml) Electrolytic enrichment Sample (600 ml) KMnO 4 0.g/00ml Na 2 O 2 0.g/00ml Distillation by rotary evaporator Collect 40 ml distillate Electrolysis Enrichment Cell Distilled H 2 O 500 ml + 2.5g Na 2 O 2 Distillation Final Volume, 50ml LSC vial Distilled water, 8ml Scintillant, 2ml Shake and stand for week Measure in LSC 2

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