Understanding Variation in Partition Coefficient, Kd, Values

Epa/Oar/Office Of Radiation And Indoor Air

Informations

• Publié par: Eftyo
• Nombre de lectures: 43
• Langue: English

Extrait

APPENDIX C d Values For Measuring Laboratory Batch K Pacific Northwest National Laboratory Standard Method Used At d 1 d 1 Washington for the measurement of K values. It is adapted from the procedure described in Relyea et al. (1980). 1.0 2.0 Spiked groundwater: Groundwater with tracer. 3.0 Methods for Determining Radionuclide Retardation Factors: Status Report C.2 . Pacific Northwest Laboratory, Richland, Washington Relyea, J. F., R. J. Serne, and D. Rai. 1980. Cognizant staff • Task leader • Responsible Staff read and understood before performing any work in the laboratory. radioactive material in the laboratory. The RWP covers a number of topics and shall be Radiation Work Procedure (RWP): This is a set of instructions for safe handling of • Blank tube: Centrifuge tube containing spiked groundwater but no solids. • • retardation events. Tracer: Radioactive element added to groundwater solution to indicate migration and • establishing chemical equilibrium with nontracer aqueous constituents. Cold wash: Contact of solid sample with nonradioactive groundwater for purposes of • Definitions consolidated, consolidated porous, and intact, impermeable geological materials. geologic material. This procedure includes descriptions for analyses of unconsolidated, loosely ’s) of This procedure describes the method for measuring radionuclide distribution coefficients (K Applicability their coworkers at the Pacific Northwest National Laboratory in Richland, The standard method reproduced below is used by the authors of this report and d Values For Measuring Laboratory Batch K At Pacific Northwest National Laboratory Standard Method Used Appendix Cd 4.0 Procedure 4.1 Groundwater Mortar and pestle Groundwater 4.2 4.3 C.3 following: samples (perform groundwater analysis within one month prior to study). Include the study perform the following analyses to characterize solid and groundwater Before the K Sample Characterization for handling. Record the number of the RWP in the laboratory record book. (RWP) which outlines the types and quantities of radionuclides permitted with instructions the possibility of contamination. Each laboratory is supplied with a radiation work procedure In using radioactive substances and/or solutions protective clothing should be used to reduce Safety Precautions Plastic bags Radioactive tracer 0.45-micrometer polycarbonate membrane filters Vacuum pipets Centrifuge Orbit shaker Teflon tape 50 ml polycarbonate centrifuge tubes with screw caps to balance for use instructions. Analytical balance (accuracy within ± 0.01 g) - Refer to operation manual specific No. 50 sieve (0.3 mm) No. 18 stainless steel sieve (1 mm) pH buffers Scintillation vials Stir bars Magnetic stirrer pH combination electrode 0-14 pH pH meter Materials3 d 3 4 3 4.3.1 For groundwater • pH , SO , CO , HCO ) 4.3.2 • Moisture content 4.4 4.4.1 Groundwater 4.4.1.1 4.4.1.2 4.4.2.1 4.4.2.2 C.4 intact material shall be preserved for dynamic testing. Disaggregation ultrasonic method or by hand with a mortar and pestle. A portion of the Loosely Consolidated Material. The sample shall be disaggregated by an from Section 4.3. 4.5.2.3. The particle size shall be determined and reported with results experiment is concluded. This condition holds for Sections 4.5.2.2 and rock with air from the time it is removed from the earth until the time the same atmospheric conditions. This requires minimum contact of the controlled atmosphere, rock samples are to be prepared under those with the material are to be conducted in an inert atmosphere or in a by passing the sample through a No. 18 stainless steel sieve. If tests millimeter (>1.0 mm), the sample shall be wet-sieved with groundwater Unconsolidated Material. To remove particles greater than one 4.4.2 Solid or altered groundwater after preparation and filtration and record results. ligand concentration) are to be studied, chemically analyze the synthetic If retardation parameters (such as pH, ionic strength, and complexing measurement. is used in a batch K Filter groundwater through a 0.45-µm polycarbonate membrane before it Sample Preparation end of this document. Record all results. Procedures which may be used to determine the above parameters are referenced at the • Particle size analysis • Cation exchange capacity • Surface area • Mineralogy For solids • bulk chemistry (Ca, Mg, Na, K, Cl, NO4.4.2.3 4.4.2.4 4.4.3 4.4.3.1 4.4.3.2 4.4.3.3 per second). 4.4.3.4 4.4.3.5 Repeated the wash procedure twice more for a total of three cold C.5 from its natural equilibrium value as measured in the field, the rock measure and record the pH of the solid-solution. If the pH has changed (nonradioactive) washes. Before the centrifuge step on the third wash, (some liquid will remain in the tube). solutions with a vacuum pipettes to prevent removal of the rock sample Next centrifuge the tubes to separate solids and liquids. Removed the placed on a shaker for a gentle overnight agitation (about one oscillation “cold” wash. The tube caps are to be replaced before the tubes are groundwater is added to each tube, including blanks with no soil, for a Thirty-milliliters of filtered, nonspiked (no radioactive tracer) threads with Teflon tape to prevent leaks. (and weights recorded) into centrifuge tubes. Wrap centrifuge tube After homogenizing, 1-g (1.0 g ± 0.01 g) samples are to be weighed are unique to each sample tube. obtaining and recording tare weights and assigning identifications which Prepare 50 ml polycarbonate centrifuge tubes with screw caps by Equilibrium obtained for each subsample to be studied. must be homogenized to insure that the same particle size distribution is After samples have been sized (Sections 4.5.2.1, 4.5.2.2 or 4.5.2.3), they between 0.30 mm and 1.00 mm. be wet sieved through a No. 50 sieve (0.30 mm) to obtain particle sizes material, such as metal filings, into the sample. The sample should then be accomplished by means that minimize the introduction of extraneous to be crushed to pass through a No. 18 sieve (<1 mm). Crushing must that simulate those in situ) for dynamic testing. The remaining sample is of the intact sample shall be preserved (and maintained under conditions Consolidated Porous Material (and intact, impermeable rock). A portion after disaggregation shall be reported with results in Section 4.3. particles >1.0 mm as in Section 4.5.2.1. The particle size distribution procedure should reduce fracturing of particles to a minimum. Remove natural grain size. Fresh surfaces will be exposed to weathering, but this shall proceed no farther than that required to reduce the sample to its2 4 4.4.4 4.5 4.5.1 4.5.2 or Pu[OH] 4.5.3 solution’s oxidation state--such as Pu(VI) to Pu(IV)--tracer should be added to groundwater. 4.5.4 4.5.5 C.6 element in groundwater. isotope of the element added with the tracer and any natural occurrence of the prior to contact with the geologic material. Additionally, report any carrier Calculate and record the amount of tracer (mol/l) present in the groundwater just geologic material. Solution is to be filtered (0.45 µm) after equilibration prior to contact with the air). Make any necessary adjustments to pH during the equilibration time. or under controlled atmosphere conditions if the aquifer is not in equilibrium with in the experiment (in equilibrium with air if the aquifer is in equilibrium with air, Allow the tracer solution to sit for at least one week under conditions to be used as possible. Otherwise, a dry, soluble, salt-free tracer shall be added to solution in as small a volume as possible with as little excess salt and acid or base that have multiple oxidation states. When drying might change the tracer stock Exception to the dry-addition rule must be made in some cases for radionuclides precipitate.) insoluble PuO procedure would be to dry plutonium basic media that would produce an by drying must be soluble in the solutions used in experimentation. (An incorrect not dry volatile tracers in acid media or they will be lost. The chemical produced Dry the tracers so that excess acid or base in the stock solution is removed. Do remain unchanged, except for the addition of the radionuclide(s) to be studied. (2) the chemical composition of the groundwater or synthetic groundwater must total amount of tracer added must be soluble in the volume of solution used and radionuclide migration studies. Two items must be carefully considered: (1) the The adding of tracer to a solution represents a critical step in the execution of Addition of Tracer volume is found by dividing the excess solution weight by the solution density. in an increased salt concentration in the remaining solution. The excess solution sample. Secure the cap of each tube to prevent evaporation, which would result weight must be recorded to determine the volume of excess solution left in each After removal of the third wash solution, each tube must be reweighed and the surfaces (either rock or cementing agents) have been exposed. occur with samples of crushed rock (Section 4.4.2.3) because fresh Continue to wash until the pH is stable. A change in pH is most likely to sample and groundwater have not yet re-established equilibrium. d d 2 d 4.6 Rock and Groundwater Contact 4.6.1 4.6.2 4.6.3 4.6.4 10,000 g (g = 980 cm/sec 5.0 5.1 5.1.1 C.7 spike (ml); (4) activity or concentration of tracer in the radioactive tracer added, V sed, (g); (3) volume of groundwater with (2) mass of solid aquifer material, M from the third cold wash (weight of excess solution divided by solution density); excess, (ml) left calculation are: (1) excess solution volume, V Data needed for K When tracer is not sorbed by blank tube wall Calculations Batch K both cases follow. variation between blanks), directly count the activity of the sample. Methods for 10 percent (using a one-tailed “t” test and combined counting error and statisti