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Information Notice No. 94-07: Solubility Criteria for Liquid Effluent Releases to Sanitary Sewerage Under the Revised 10 CFR Part 20
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS WASHINGTON, D.C. 20555 January 28, 1994 NRC INFORMATION NOTICE 94-07: SOLUBILITY CRITERIA FOR LIQUID EFFLUENT RELEASES TO SANITARY SEWERAGE UNDER THE REVISED 10 CFR PART 20 Addressees All byproduct material and fuel cycle licensees with the exception of licensees authorized solely for sealed sources. Purpose The U.S. Nuclear Regulatory Commission is issuing this information notice to emphasize the changes in 10 CFR Part 20 with respect to liquid effluent releases to sanitary sewerage and to encourage you to prepare for these revisions.* It is expected that licensees will review this information for applicability to their operations, distribute it to appropriate staff, and consider actions to prepare for, and incorporate, these changes. Suggestions contained in this information notice are only recommendations; therefore, no specific action nor written response is required. Background On December 21, 1984, NRC released an information notice documenting several instances of reconcentration of radionuclides released to sanitary sewerage (IN No. 84-94, "Reconcentration of Radionuclides Involving Discharges into Sanitary Sewage Systems Permitted under 10 CFR 20.303"). Several other instances have since occurred in Portland, Oregon; Ann Arbor, Michigan; Erwin, Tennessee; and Cleveland, Ohio. The primary contributors, in some of these cases, appear to have been insoluble materials released as dispersible particulates or flakes. This issue was addressed again on May 21, 1991, by NRC, when it published its revision of Part 20 in the Federal Register (56 FR 23360), which removed insoluble non-biological material from the types of material that may be released to sanitary sewerage. Relative to this issue, the NRC Office of Nuclear Regulatory Research is conducting a study to clarify the mechanisms underlying reconcentration in sanitary sewerage and sewage treatment facilities. 9401240059 * Sanitary sewerage is defined by 10 CFR 20.1003 as "a system of public sewers for carrying off waste water and refuse, but excluding sewage treatment facilities, septic tanks, and leach fields owned or operated by the licensee [emphasis added]." . IN 94-07 January 28, 1994 Page 2 of 5 Description of Circumstances To help prevent further reconcentration incidents at public sewage treatment facilities, 10 CFR 20.2003(a)(1), effective January 1, 1994, was written as follows: 20.2003 Disposal by release into sanitary sewerage (a) A licensee may discharge licensed material into sanitary sewerage if each of the following conditions is satisfied: (1) The material is readily soluble (or is readily dispersible biological material) in water; and... However, this revision to Part 20 did not contain an operational definition of solubility, and this precipitated many questions, from licensees, concerning how the solubility of a material may be demonstrated. Without the ability to demonstrate compliance, these licensees were unable to determine whether new procedures should be developed, new treatment systems installed, or whether they should apply for an exemption, based on the principle of maintaining all doses as low as is reasonably achievable (ALARA). Discussion In some of the known reconcentration incidents, the greatest reconcentrations appear to have been due to compounds released to sanitary sewerage that were not soluble. There are many approaches that may be used to determine a chemical compound's solubility in water. The following discusses two of the more common approaches: 1. Direct Determination of Compound Solubility Class, Formal Solubility, or Solubility Product (Ksp) This approach would be applicable whenever there is sufficient knowledge of the chemical form of all materials contained in the liquid effluent at the point of release. With this knowledge, it would be possible to use one (or more) of the following methods: (a) Solubility Class Determination: The solubility class of the compound to be released could be determined directly from common literature data (e.g., Handbook of Chemistry and Physics - CRC Press, and Lange's Handbook of Chemistry - McGraw- Hill Book Company). If a compound is classified as "v s" (very soluble) or "s" (soluble), this would indicate the compound is "readily soluble." On the other hand, if it is classified as "i" (insoluble), "sl s" (slightly soluble), or "v sl s" (very slightly soluble), this would indicate materials that are "not readily soluble." Certain compounds are designated as class "d" (decompose). If the decomposed species of these compounds are classified as either "v s" or "s," this would indicate that the parent compound is "readily soluble." If these decomposed species are simple ions, such compounds (class "d") should be considered "readily soluble.". IN 94-07 January 28, 1994 Page 3 of 5 (b) Solubility Product (Ksp) Determination: The solubility product constant of the compound could also be used to determine if a compound is readily soluble in water. The solubility product constant, Ksp, for a strong electrolyte MmAa, is expressed as: m a Ksp = [M] [A] where [M] and "m" are the ionic concentration (mole/liter) and the number of moles, respectively, of the dissolved cation; and [A] and "a" are the ionic concentration and the number of moles, respectively, of the dissolved anion. For a simple electrolytic compound, with one mole of a dissolved cation species and one mole of a dissolved anion species, a Ksp 2 2 greater than 1.00 E-05 mole /liter would indicate that a compound is "readily soluble." For other compounds with more complex dissolution reactions (i.e., more than one mole dissolved for each species and/or more anionic or cationic species present in the dissolved products), the Ksp constant would increase exponentially, based on the number of moles and/or the number of dissociated species. For example, if three moles are present (two for the anion and one for the cation), the unit of Ksp would be 3 3 3/2 mole /liter , and the corresponding Ksp would be (1 E-05) or 3 3 3.2 E-08 mole /liter ; the same principle could be applied for more complex dissolution reactions. (c) Formal Solubility Determination: Compound solubilities (g/100 ml or mole fraction per 100 ml) are also listed in the chemical literature. From a review of general scientific literature, "formal solubilities"** greater than 0.003 mole/liter would indicate that a compound is "readily soluble." ** The general relation between the formal solubility, Sf, and the solubility product, Ksp, of a strong electrolyte MmAa in water is given by: m a 1/(m+a) Sf = (Ksp/(m a )), where Ksp is the solubility product, [M] is the molar concentration of the metal ion (cation), [A] is the molar concentration of the anion, "m" is the number of moles of dissolved cation per mole of dissolved substance, and "a" is the number of moles of the dissolved anion per mole of dissolved substance. For further discussion on the determination of solubility products and formal solubility, refer to Chapter 6, "Precipitation and Dilution," from Water Chemistry, by Vernon L. Snoeyink and David Jenkins (John Wiley and Sons: 1983) or texts relating to physical and/or analytical chemistry.. IN 94-07 January 28, 1994 Page 4 of 5 Formal solubilities less than 0.003 mole/liter would indicate compounds that are "not readily soluble." It should be pointed out that all values mentioned above (e.g., solubility class, formal solubility, and solubility product) correspond to measurements taken under standard conditions (e.g., 25�C, 101.3 kPa, pH of 7, and Eh of 0). 2. Filtration and Radiometric Analysis of Suspended Solids This approach may be used if knowledge of the chemical form of all materials contained in the liquid effluent at the point of release is incomplete. It is most applicable when releases are made in a batch mode. This approach involves the use of standard laboratory procedures to test representative samples of the waste stream for the presence of suspended radioactive material. The following two laboratory procedures were developed specifically to determine the suspended solids content of water: ASTM Method D 1888- 78, "Standard Test Methods for Particulate and Dissolved Matter, Solids, or Residue in Water," and the American Public Health Association's Method 7110, "Gross Alpha and Gross Beta Radioactivity (Total, Suspended, and Dissolved)" from Standard Methods for the Examination of Water and Wastewater. It should be noted that ASTM Method D 1888-78 was developed to measure the total suspended solids content of water, not just the radioactive portion. In either case, activity in the suspended solids portion of effluent greater than that found in similarly processed background water samples would indicate the presence of insoluble radioactive material. Whether one of the above approaches or a self-developed alternative is used, it is a good health physics practice to document this approach in the form of a procedure. Procedures such as these usually include provisions for the documentation of any models, calculations, analytical measurements, and/or quality control measures used. This information is usually maintained with the applicable release records, to demonstrate that the developed procedure will ensure compliance with the regulations. If material to be released would not qualify as being "readily soluble," 10 CFR 20.2003(a)(1) would prohibit release to sanitary sewerage unless an exemption has been granted. Exemptions will be judged on a case-by-case basis, when it is demonstrated that release to sanitary sewerage is in accordance with the ALARA principle, consistent with applicable regulations, and in the public interest. It is expected that licensees will review this information for applicability to their operations, and consider actions, as appropriate to their licensed activities. However, suggestions contained in this information notice are not NRC requirements; therefore, no specific action nor written response is required. . IN 94-07 January 28, 1994 Page 5 of 5 If you have any questions about the information in this information notice, please contact one of the technical contacts listed below or the appropriate regional office. /s/'d by RFBurnett /s/'d by CJPaperiello Robert F. Burnett, Director Carl J. Paperiello, Director Division of Fuel Cycle Safety Division of Industrial and and Safeguards Medical Nuclear Safety Office of Nuclear Material Office of Nuclear Material Safety and Safeguards Safety and Safeguards Technical contacts: Rateb (Boby) Abu-Eid, NMSS (301) 504-3446 Cynthia G. Jones, NMSS (301) 504-2629 Attachments: 1. List of References 2. List of Recently Issued NMSS Information Notices 3. List of Recently Issued NRC Information Notices. Attachment 1 IN 94-07 January 28, 1994 Page 1 of 1 REFERENCES Annual Book of ASTM Standards. Volume 11.01, "Water (I)." American Society for Testing and Materials, Easton, MD, 1989. CRC Handbook of Chemistry and Physics. CRC Press, Inc., Boca Raton, FL, 65th ed, 1984. Lange's Handbook of Chemistry. McGraw-Hill, Inc., New York, NY, 13th ed, 1985. Snoeyink, Vernon L. and David Jenkins, Water Chemistry. John Wiley & Sons, Inc., New York, NY, 1980. Standard Methods for the Examination of Water and Wastewater. American Public Health Association, Washington, DC, 17th ed, 1989.
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