ML20133G443
| ML20133G443 | |
| Person / Time | |
|---|---|
| Issue date: | 10/04/1985 |
| From: | Costanzi F NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Knapp M NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| Shared Package | |
| ML20133G447 | List: |
| References | |
| NUDOCS 8510150467 | |
| Download: ML20133G443 (20) | |
Text
{{#Wiki_filter:- i OCT 4 1985 MEMORANDUM FOR: Malcolm R. Knapp, Chief Geotechnical Branch Division of Waste Management, NMSS FROM: Frank A. Costanzi, Chief Waste Management Branch Division of Radiation Programs and Earth Sciences, RES 4
SUBJECT:
REVIEW 0F DRAFT GENERIC TECHNICAL POSITION (GTP) ON THE DETERMINATION OF RADIONUCLIDE SORPTION FOR ASSESSMENT OF HIGH LEVEL WASTE ISOLATION (0.P. GT02/532322 7) i h Per your request, my staff has reviewed the draft technical position on the " Determination of Radionuclide Sorption for Assessment of High Level Waste Isolation." We offer the following general comments. Radionuclide sorption involves multiple physical and chemical processes. We suggest some discussion of sorption mechanisms be-included, because we feel that the approach taken in the draft could leave the reader with the impression that sorption can be measured as a single parameter. Further, the single parameter approach, commonly known as the Kd or Rd approach, has produced empirical results which could not be extrapolated or interpolated to any conditions other than those of the experiment. Moreover, the matrix of experiments needed to employ the empirical approach at a specific site would be extremely large and probably not practical. We propose _that the technical position be revised to recommend taking a mechanistic approach to characterizing sorption. The technical position does not need to identify all the sorption mechanisms, but should stress that DOE needs to identify the important mechanisms. We also suggest that you consider that the technical position recommend that the applicant make use of sorption theory in designing sorption experiments. Further, it might be useful to have someone like Dr. James Leckie of Stanford University, an NMSS subcontractor who is an expert on sorption, review critically the revised document prior to solicitation of public comments. Finally, we believe that the organization of the draft technical position would be improved by rearranging topics so that sorption theory, experimental _ design, analytical methods, field tests, kinetics / natural analogues, and quality assurance are presented in individual sections. i 8510150467 851004 PDR MISC l 8510150467 PDR l l
@ KfG 4 'o UNITED STATES 8 NUCLEAR REGULATORY COMMISSION { E WASHINGTON, D. C. 20555 \\..... p OCT 4 1985 MEMORANDUM FOR: Malcolm R. Knapp, Chief Geotechnical Branch Division of Waste Management, NMSS FROM: Frank A. Costanzi, Chief l Waste Management Branch Division of Radiation Programs and Earth Sciences, RES
SUBJECT:
REVIEW 0F DRAFT GENERIC TECHNICAL POSITION (GTP) ON THE DETERMINATION OF RADIONUCLIDE SORPTION FOR ASSESSMENT OF HIGH LEVEL WASTE ISOLATION (0.P. GT02/532322-7) Per your request, my staff has reviewed the draf t technical position on the " Determination of Radionuclide Sorption for Assessment of High Level Waste Isolation." We offer the following generi.1 comments. Radionuclide sorption involves multiple physical and chemical processes. We suggest some discussion of sorption mechanisms be included, because we feel that the approach taken in the draft could leave the reader with the impression that sorption can be measured as a single parameter. Further, the single parar.eter approach, commonly known as the Kd or Rd approach, has produced empirical results which could not be extrapolated or interpolated to any conditions other.than those of the experiment. Moreover, the matrix of experiments needed to employ the empirical approach at a specific site would be extremely large and probably not practical. We propose that the technical position be revised to recommend taking a mechanistic approach to characterizing sorption. The technical position does not need to identify all the sorption mechanisms, but should stress that DOE needs to identify the important mechanisms. We also suggest that you consider that the technical position recomend that the applicant make use of sorption theory in designing sorption experiments. Further, it might be useful to have someone like Dr. James Leckie of Stanford University, an NMSS subcontractor who is an expert on sorption, review critically the revised document prior to solicitation of public comments. Finally, we believe that the organization of the draft technical position would be improved by rearranging topics so that sorption theory, experimental design, analytical methods, field tests, kinetics / natural analogues, and quality assurance are presented in individual sections. 1 ~. _-.y . _. ~, .~r-, ,. ~.,
_ - _ -. _. = - - - 1 OCT 4IW3 i 4 I l, i We would be pleased to review a revised document should you so desire. Dr. George Birchard of my staff will be glad to assist you with implementing any of our raggestions. Specific detailed comments are enclosed. A marked-up copy of the draft GTP has been provided to John Bradbury. ) Original Signed By: Frank A. Costanzi Frank A. Costanzi, Chief Waste Management Branch l j Division of Radiation Programs and Earth Sciences, RES
Enclosures:
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l 1 analytical methods, field tests, kinetics / natural analogues, and quality assurance are presented in individual sections. We would be pleased to review a revised document should you so desire. Dr. George Birchard of my staff will be glad to assist you with implementing any of cur suggestions. Specific detailed comments are enclosed. Frank A. Costanzi, Chief Waste Management Branch Division of Radiation Programs and Earth Sciences, RES
Enclosures:
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1 i 2 t 4 We would be pleased to review a revised document should you so desire. Dr. George Birchard of my staff will be glad to assist you with implementing any of cur suggestions. Specific detailed coments are encl ed. A marked-up copy i of the draft GTP has been provided to h Br ' (i / (, x t /v i Frank A. #Costanz l Chief Waste Management Branch Division of Radiation Programs and Earth Sciences, RE3
Enclosures:
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4 i I SPECIFIC COMMENTS l i j 1.2 Definitions Sorption - In the definition of sorption the processes or types of processes are not specified. The definition is potentially misleading in that it states i that radionuclides are " removed from a liquid phase" by sorption. Sorption i only partially removes radionuclides from solution whereas the definition could i be mistaken easily to mean that removal is total. Processes which " remove" l radionuclides from a liquid phase, which are neither sorption nor precipitation, such as ultrafiltration of radionuclide bearing colloids pseudocolloids and particulates are incorrectly defined as being sorption. Sorption Capacity - The term " cation exchange capacity" (CEC) is commonly used in the literature whereas " sorption capacity" is not used. The definition.for " Sorption capacity" provided is not technically sound. It is stated in terms of a radionuclide concentration, not the elemental concentration. As defined, j it is a capacity for only the specific aqueous composition of the experiment 1 and, as defined, different experimenters could determine different capacities l for the same material based upon different sample preparation procedures, i Therefore, the term " sorption capacity" should be dropped and replaced by i " cation exchange capacity" with a suitable definition consistent with definitions in the technical literature. i 1.3 Use of Sorption j j A substantial part of this subsection is either redundant or unclear. i Suggested changes have been made on the marked-up draft. l l 1.4 Regulatory Framework l 4 The fourth sentence which states that "The DOE has the lead responsibility for i formulating national policy for disposal of HLW,..." is in error. Congress } determines national policy and the Nuclear Waste Policy Act is the document j that states the policy. 00E has program responsibility. j
2.0 Background
I Extensive comments are provided in the mark-up. The most significant points about this section are (1) the notion of a " safety factor"; and (2) the i statement that "It is the responsibility of the DOE to decide when and how much credit will be taken for sorption to meet NRC and EPA criteria for radionuclide i release. Sorption need not be considered if other features of the repository l are adequate to meet the criteria." i 1) 10 CFR 60 and the draf t EPA standard do not use the notion of a " safety ( factor". The concept of a " safety factor" should be avoided because in 1u.
i the present context it does not have a clear relationship to safety and would therefore be a basis for unwanted and unnecessary contention. 2) Ultimately, the NRC will have to determine whether or not the DOE license application meets NRC and EPA criteria. Because confidence, including redundancy, is a critical aspect of establishing reasonable assurance, which is the basis for license application approval, sorption is a factor that will need to be considered in evaluating the license application. Moreover, sorption is a process which is specified explicitly in the 10 CFR 60 favorable and potentially adverse conditions. Therefore any statement that implies that the DOE has the option of not considering sorption in its license application is misleading and erroneous. Not taking " credit" for sorption is not the same as not considering sorption. 2.1 Experimental Approaches for Sorption Determination The description of sorption experiments as involving "radionuclide free" or "radionuclide bearing" solids or solutions is imprecise because (1) radioisotopes need not be used to assess radionuclide behavior; (2) radionuclides or associated stable isotopes may be present in both the solution and on the solid phase in a sorption experiment and a spike of a specific radionuclide may be added; and (3) different radioisotopes for the same element may be sorbed and desorbed concurrently. The paragraph on the comparative advantages of the approaches is inaccurate with respect to the statement on solution residence time. Both batch and column experiments can be run for as long a time as the experimenter is willing to wait. Column tests can be run at extermely low flow rates for extremely long times if close simulation of repository conditions is desired. The main advantages of batch tests are that they are (1) cheap, (2) simple, and (3) better suited to mass production than column tests. 3.0 Statement of Position f The fundamental deficiency of the Statement of Position is that it does not recomend that DOE establish a scientifically sound theoretical basis for the sorption experiments. The statement, "It is the position of the NRC that sorption parameters used in performance assessment calculations should be derived experimentally." could be interpreted as meaning that an empirical program to generate batch "Kd" values such as the ' WRIT' program is acceptable to the NRC. The five listed items that follow in the Statement of Position also would appear to endorse this approach, Failure of the WRIT program is well documented in Relyea, Serne and Rai (1980) and Relyea (1980). The basic reason that the WRIT program failed is that batch sorption measurements produce results that are not adequate for predicting radionuclide transport under HLW site conditions (Carnahan,1984). Moreover, the opening statement in the Statement of Position appears to preclude the use of in-situ observed distribution coefficients and natural analogue data. In-situ distribution coefficients such as those j developed for the Palo Ouro Basin (Hubbard, Laul and Perkins, 1984) appear to be a source of information on sorption kinetics in addition to being useful sorption data. In-situ natural radionuclide data and other natural analogue data are encouraged in the discussion section (4.) and in item 4) of the i 2 i
Position. The opening sentence should be rewritten to eliminate the apparent inconsistency. The Statement of Position does not take a position on field testing to develop irformation on sorption. Sorption cannot be realistically considered as separable from transport. Field testing is an essential part of developing a credible sorption data base, especially in fractured rocks for which interaction between the fluid and the host rock cannot be modeled by either a batch or column experiment because fracture flow and sorption into fractures are processes which are not well enough understood to be realistically scaled down to the laboratory. Therefore, field testing is essential and the statement of position should state that field testing is essential. In item 4) of the Statement of Position in situ field tests and natural analogues are " included" as ways of determining the applicability of sorption parameters. This statement does not convey the point that field tests and analogues are essential methods for measuring and characterizing sorption. ] In sum, the statement of position should require that the applicant has a theoretical basis for the experimental design. If the DOE takes a strictly empirical approach the data will only be useful for the predicting the behavior of a radionuclide under the precise conditions of the laboratory experiment. 4.0 Discussion The term " safety factor" should be dropped as previously mentioned. The phrase " provide reasonable assurance" should be replaced by " demonstrate" because the DOE does not " provide reasonable assurance", the licensing processes establishes and defines it. i 4.1 Matrix Development The proposed matrix of experiments could have millions of elements, at least, if a range of compositional variables were considered. "Considering the dependence or interrelation of phases and conditions upon each other and deleting incompatible combinations" would reduce the matrix size greatly as suggested, but not sufficiently to make the number of elements practicable. A theoretical approach which establishes the relationships between sorption and the experimental values is needed to reduce the number of experiments to a reasonable value. One problem with the WRIT "Kd predictor" approach was that, without a theoretical basis for reducing the number of measurements, not enough measurements could be taken to make a good prediction of "Kd". The words "with reasonable assurance" in the last sentence of 4.1 should be l deleted. l 4.2 Characterization of Reactants and Products RES agrees that careful characterization and control of experiments is necessary. Characterization of the sorption products cannot be done easily because sorption involves reactions on surfaces. Adequate characterization of products involves indirect measurements such as desorption, autoradiography and selective leaching, and direct measurements of surface properties by methods such as ESCA and Auger spectroscopy. Interpreting the results of measurements l l 3 1
~ of surface properties cnd leaching will involve modelling the surface reactions. The technical position should give more guidance on the methods for characterizing reaction products and identification of the mechanisms of sorption. The present guidance which recormiends determining the composition of individual solid phases, surface area and particle size, if strictly followed would provide inadequate information to meet the objective of " determining which reactions took place and how these reactions depend on experimental techniques." With regard to the sentence "The applicability of crushed solids in sorption experiments to repository conditions should be addressed.", we suggest that it be revised to: "The DOE should provide proof that sorption in the laboratory on crushed solids is relevant to sorption at the repository site." 4.3 Isotherm Development for Closed-System Experimentation Closed System (or batch) experiments are usually inadequate for assessing i speciation effects. This section should stress that the isotherms must be measured in such a way that multiple species do not get lumped together in one isotherm. If multiple species get lumped together unwittingly the isotherm probably will not be reproducible. Editorial changes to strengthen the position that the effects of concentration on sorption be considered are in the last paragraph of Section 4.3 of the mark-up. 4.4 Determination of Sorption Parameters by Multiple Experimental Approaches ) A number of very important topics have been lumped together in this section. Because of the organization of this section several topics are given only the most cursory treatment. The material which is discussed is presented in a laundry-list fashion that indiscriminate 1y lumps the most important and least important topics together. Two important topics, water / rock ratio and use of crushed rock to evaluate sorption in fractures, are buried in a paragraph about scaling. The argument about water / rock ratio and crushed rock vs. fracture filling material which straddles pp 9-10 is extremely important. However, the arguments are presented in an either/or fashion, as if DOE could comfortably pick either point of view and be acceptable to the NRC. When giving guidance, it might be better to state explicitly that the NRC endorses a particular point of view. 1 Scientific aspects of quality assurance such as laboratory intercomparison, peer review and journal publication of results are not mentioned. The change in repository conditions over time is not discussed. Kinetics and natural analogues, experimental design, quality assurance, repository evolution over time, water / rock ratio, and field tests are important subjects that should be treated in detail in separate sections. On the other hand the subject of the section " Determination of Sorption Parameters by Multiple Experimental Approaches" is one of the scientific components of quality assurance which should be a part of the quality assurance section. 4 l l
4.5 Documentation of Uncertainties The topic of this section is actually a subset of the topic of quality assurance. Quality assurance should be presented in a scientific fashion in the technical position rather than as a bookkeeping and auditing function. The docur.entation and scientific investigatien of uncertainties is an important scientific aspect of assuring the quality of data and reduction of the misuse of data. l 5 l l
REFERENCES Relyea, J. F. (1980), Third Contractor Information Meeting Vol. 1, Pacific Northwest Laboratory, PNL-SA-8571. Relyea, J. F., R. J. Serne and D. Rai (1980), Methods for Determining Radionuclide Retardation Factors: Status Report, Pacific Northwest Laboratory, PNL-3349/UC-70. Carnahan, C. L., C. W. Miller and J. S. Remer (1984), Verification and Improvement of Predictive Algorithims for Radionuclide Migration pp 416-439 in NRC Nuclear Waste Geochemistry '83, U. S. Nuclear Regulatory Commission NUREG/CP-0052, Alexander and Birchard editors.
- Hubbard, N., J. C. Land and R. W. Perkins (1984), The Use of Natural Radionuclides in Far-Field Aquifers, Mat. Rec. Soc. Surp. Proc. Vol. 26 Elsevier Publishing Co.
1 i 6
M4M o We would be pleased to review a revised document should you so desire. Dr. George Birchard of my staff will be glad to assist you with implementing any of our suggestions. Specific detailed comments are enclosed. A marked-up copy of the draft GTP has been provided to John Bradbury. Original Signed By: Frank A.Costanzi Frank A. Costanzi, Chief Waste Management Branch Division of Radiation Programs and Earth Sciences, RES
Enclosures:
Specific Comments DISTRIBUTION: Subj. Rdg. Cir. Chron. GBirchard W0tt FCostanzi Econti KGoller Dross ' rr r4 ~~-"c, RMinogue e.-.i; i., #. ~~ 2 % cct T G r ::c. y T. - t-r;, - - - - ~ ..v. -.~ t.: - I-I }. w ^- 7p g-...- - ..q. i
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4 analytical methods, field tests, kinetics / natural analogues, and quality assurance are presented in individual sections. We would be pleased to review a revised document should you so desire. Dr. George Birchard of my staff will be glad to assist you with implementing any of our suggestions. Specific detailed comments are enclosed. Frank A. Costanzi, Chief Waste Management Branch Division of Radiation Programs and Earth Sciences, RES
Enclosures:
1. Mark-up Copy 2. Specific Comments DISTRIBUTION: 1, Subj. Rdg. Cir. A,' Chron. GBirchard \\' W0tt FCostanzi EConti KGoller Dross RMinogue ) 0FC: WMB:dm'
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OCT 4 1985 MEMORANDUM FOR: Malcolm R. Knapp, Chief Geotechnical Branch Division of Waste Management, NMSS FROM: Frank A. Costanzi, Chief Waste Management Branch Division of Radiation Programs and Earth Sciences, RES
SUBJECT:
REVIEW 0F DRAFT GENERIC TECHNICAL POSITION (GTP) ON THE DETERMINATION OF RADIONUCLIDE SORPTION FOR ASSESSMENT OF HIGH LEVEL WASTE ISOLATION (0.P. GT02/532322-7) Per your request, my staff has reviewed the draft technical position on the " Determination of Radionuclide Sorption for Assessment of High Level Waste Isolation." We offer the following general comments. Radionuclide sorption involves multiple physical and chemical processes. We suggest some discussion of sorption mechanisms be included, because we feel that the approach taken in the draft could leave the reader with the impression that sorption can be measured as a single parameter. Further, the single parameter approach, commonly known as the Kd or Rd approach, has produced empirical results which could not be extrapolated or interpolated to any conditions other than those of the experiment. Moreover, the matrix of experiments needed to employ the empirical approach at a specific site would be extremely large and probably not practical. We propose that the technical position be revised to recommend taking a mechanistic approach to characterizing sorption. The technical position does not need to identify all the sorption mechanisms, but should stress that DOE needs to identify the important mechanisms. We also suggest that you consider that the technical position recommend that the applicant make use of sorption theory in designing sorption experiments. Further, it might be useful to have someone like Dr. James Leckie of Stanford University, an NMSS subcontractor who is an expert on sorption, review critically the revised document prior to solicitation of public comments. Finally, we believe that the organization of the draft technical position would be improved by rearranging topics so that sorption theory, experimental design, analytical methods, field tests, kinetics / natural analogues, and quality assurance are presented in individual sections.
SPECIFIC COMMENTS 1.2 Definitions Sorption - In the definition of sorption the processes or types of processes are not specified. The definition is potentially misleading in that it states that radionuclides are " removed from a liquid phase" by sorption. Sorption only partially removes radionuclides from solution whereas the definition could be mistaken easily to mean that removal is total. Processes which " remove" radionuclides from a liquid phase, which are neither sorption nor precipitation, such as ultrafiltration of radionuclide bearing colloids pseudocolloids and particulates are incorrectly defined as being sorption. Sorption Capacity - The term " cation exchange capacity" (CEC) is commonly used, in the literature whereas " sorption capacity" is not used. The definition for " Sorption capacity" provided is not technically sound. It is stated in terms of a radionuclide concentration, not the elemental concentration. As defined, it is a capacity for only the specific aqueous composition of the experiment and, as defined, different experimenters could determine different capacities for.the same material based upon different sample preparation procedures. Therefore, the term " sorption capacity" should be dropped and replaced by " cation exchange capacity" with a suitable definition consistent with definitions in the technical literature. 1.3 Use of, Sorption A substantial part of this subsection is either redundant or unclear. Suggested changes have been made on the marked-up draft. 1.4 Regulatory Framework The fourth sentence which states that "The DOE has the lead responsibility for formulating national policy for disposal of HLW,..." is in error. Congress determines national policy and the Nuclear Waste Policy Act is the document that states the policy. DOE has program responsibility.
2.0 Background
Extensive comments are provided in the N rk-up. The most significant points about this section are (1) the noth', W a " safety factor"; and (2) the statement that "It is the respo @ v.U. of the DOE to decide when and how much credit will be taken for sorpti,n a r v. NRC and EPA criteria for radionuclide release. Sorption need not be considerect if other features of the repository are adequate to meet the criteria." 1) 10 CFR 60 and the draf t EPA standard do not use the notion of a " safety factor". The concept of a " safety factor" should be avoided because in l l
the present context it does not have a clear relationship to safety and would therefore be a basis for unwanted and unnecessary contention. 2) Ultimately, the NRC will have to determine whether or not the DOE license application meets NRC and EPA criteria. Because confidence, including redundancy, is a critical aspect of establishing reasonable assurance, which is the basis for license application approval, sorption is a factor that wH1 need to be considered in evaluating the license application. Moreover, sorption is a process which is specified explicitly in the 10 CFR 60 favorable and potentially adverse conditions. Therefore any statement that implies that the DOE has the option of not considering sorption in its license application is misleading and erroneous. Not taking " credit" for sorption is not the same as not considering sorption. 2.1 Experimental Approaches for Sorption Determination The description of sorption experiments as involving "radionuclide free" or "radionuclide bearing" solids or solutions is imprecise because (1) radioisotopes need not be used to assess radionuclide behavior; (2) radionuclides or associated stable isotopes may be present in both the solution and on the solid phase in a sorption experiment and a spike of a specific radionuclide may be added; and (3) different radioisotopes for the same element may be sorbed and desorbed concurrently. The paragraph on the comparative advantages of the approaches is inaccurate ,with respect to the statement on solution residence time. Both batch and . column experiments can be run for as long a time as the experimenter is willing to wait. Column tests can be run at extermely low flow rates for extremely long times-if close simulation of repository conditions is desired. The main advantages of batch tests are that they are (1) cheap, (2) simple, and (3) better suited to mass production than column tests. 3.0 Statement of Position The fundamental deficiency of the Statement of Position is that it does not recomend that DOE establish a scientifically sound theoretical basis for the sorption experiments. The statement, "It is the position of the NRC that sorption parameters used in performance assessment calculations should be derived experimentally." could be interpreted as meaning that an empirical program to generate batch "Kd" values such as the ' WRIT' program is acceptable to the NRC. The five listed items that follow in the Statement of Position also would appear to endorse this approach. Failure of the WRIT program is well documented in Relyea, Serne and Rai (1980) and Relyea (1980). The basic reason that the WRIT program failed is that batch sorption measurements produce results that are not adequate for predicting radionuclide transport under HLW site conditions (Carnahan,1984). Moreover, the opening statement in the Statement of Position appears to preclude the use of in-situ observed distribution coefficients and natural analogue data. In-situ distribution coefficients such as those developed for the Palo Duro Basin (Hubbard, Laul and Perkins, 1964) appear to be a source of information on sorption kinetics in addition to being useful sorption data. In-situ natural radionuclide data and other natural analogue data are encouraged in the discussion section (4.) and in item 4) of the 2
.= Position. The opening sentence should be rewritten to eliminate the apparent inconsistency. T5e Statement of Position does not take a position on field testing to develop information on sorption. Sorption cannot be realistically considered as separable from transport. Field testing is an essential part of developing a credible sorption data base, especially in fractured rocks for which interaction between the fluid and the host rock cannot be modeled by either a batch or column experiment because fracture flow and sorption into fractures are processes which are not well enough understood to be realistically scaled down to the laboratory. Therefore, field testing is essential and the statement of position should state that field testing is essential. In item 4) of the Statement of Position in situ field tests and natural analogues are " included" as ways of determining the applicabil ny of sorption parameters. This statement does not convey the point that field tests and analogues are essential methods for measuring and characterizing sorption. t In sum, the statement of position should require that the applicant has a theoretical basis for the experimental design. If the DOE takes a strictly empirical approach the data will only be useful for the predicting the behavior of a radionuclide under the precise conditions of the laboratory experiment. 4.0 Discussion The term " safety factor" should be dropped as previously mentioned. The phrase " provide reasonable assurance" should be replaced by " demonstrate" because the DOE does not " provide reasonable assurance", the licensing processes establishes and defines it. 4.1 Matrix Development The proposed matrix of experiments could have millions of elements, at least, if a range of compositional variables were considered. "Considering the dependence or interrelation of phases and conditions upon each other and deleting incompatible combinations" would reduce the matrix size greatly as suggested, but not sufficiently to make the number of elements practicable. A theoretical approach which establishes the relationships between sorption and the experimental values is needed to reduce the number of experiments to a reasonable value. One problem with the WRIT "Kd predictor" approach was that, without a theoretical basis for reducing the number of measurements, not enough measurements could be taken to make a good prediction of "Kd". The words "with reasonable assurance" in the last sentence of 4.1 should be celeted. 4.2 Characterization of_R_eactants and Products RES agrees that careful characterization and control of experiments is necessary. Characterization of the sorption products cannot be done easily because sorption involves reactions on surfaces. Adequate characterization of products involves indirect measurements such as desorption, autoradiography and selective leaching, and direct measurements of surface properties by methods such as ESCA and Auger spectroscopy. Interpreting the results of measurements 3
of surface properties and leaching will involve modelling the surface reactions. The technical position should give more guidance on the methods for characterizing reaction products and identification of the mechanisms of sorption. The present guidance which recommends determining the composition of individual solid phases, surface area and particle size, if strictly followed would provide inadequate information to meet the objective of " determining which reactions took place and how these reactions depend on experimental techniques." With regard to the sentence "The applicability of crushed solids in sorption experiments to repository conditions should be addressed.", we suggest that it be revised to: "The DOE should provide proof that sorption in the laboratory on crushed solids is relevant to sorption at the repository site." 4.3 Isotherm Development for Closed-System Experimentation Closed System (or batch) experiments are usually inadequate for assessing speciation effects. This section should stress that the isotherms must be measured in such a way that multiple species do not get lumped together in one isatherm. If multiple species get lumped together unwittingly the isotherm probably will not be reproducible. Editorial changes to strengthen the position that the effects of concentration on sorption be considered are in the last paragraph of Section 4.3 of the mark-up. Determination of Sorption _ Parameters by_ Multiple Experimental Approaches 4.4 f A number of very important topics have been lumped together in this section. Because of the organization of this section several topics are given only the most cursory treatment. The material which is discussed is presented in a i laundry-list fashion that indiscriminately lumps the most important and least important topics together. Two important topics, water / rock ratio and use of crushed rock to evaluate sorption in fractures, are buried in a paragraph about scaling. The argument about water / rock ratio and crushed rock vs. fracture filling material which straddles pp 9-10 is extremely important. However, the arguments are presented in an either/or fashion, as if DOE could comfortably pick either point of view and be acceptable to the NRC. When giving guidance, it might be better to state explicitly that the NRC endorses a particular point of view. Scientific aspects of quality assurance such as laboratory intercomparison, peer review and journal publication of results are not mentioned. The change in repository conditions over time is not discussed. Kinetics and natural analogues, experimental design, quality assurance, repository evolution over time, water / rock ratio, and field tests are important subjects that should be treated in detail in separate sections. On the other hand the subject of the section " Determination of Sorption Parameters by Multiple Experimental Approaches" is one of the scientific components of quality assurance which should be a part of the quality assurance section. 4 4
4.5-Documentation of Uncertainties The topic of this section is actually a subset of the topic of quality assurance. Quality assurance should be presented in a scientific fashion in the technical position rather than as a bookkeeping and auditing function. The documentation and scientific investigation of uncertainties is an important scientific aspect of assuring the quality of data and reduction of the misuse of data. 5
t. 1 REFERENCES Relyea, J. F. (1980), Third Contractor Information Meeting Vol.1, Pacific Northwest Laboratory, PNL-SA-8571. Relyea, J. F., R. J. Serne and D. Rai (1980), Methods for Determining Radionuclide Retardation Factors: Status Report, Pacific Northwest Laboratory, PNL-3349/UC-70. 4 Carnahan, C. L., C. W. Miller and J. S. Remer (1984), Verification and Improvement of Predictive Algorithims for Radionuclide Migration pp 416-439 in NRC Nuclear Waste Geochemistry '83, U. S. Nuclear Regulatory Commission NUREG/CP-0052, Alexander and Birchard editors. Hubbard, N., J. C. Land and R. W. Perkins (1984), The Use of Natural Radionuclides in Far-Field Aquifers, Mat. Rec. Soc. Sump. Proc. Vol. 26, Elsevier Publishing Co. i i i 1 l 4 6 4 7 -,_,,.r_r.--- .mm.. , _ _ ~ -,_,m.,..,m- -}}