§ 191.16 Alternative provisions for dis- The Administrator may, by rule, sub- (a) The alternative provisions have been proposed for public comment in the FEDERAL REGISTER together with information describing the costs, risks, and benefits of disposal in accordance with the alternative provisions and the reasons why compliance with the existing provisions of Subpart B appears inappropriate; (b) A public comment period of at least 90 days has been completed, during which an opportunity for public hearings in affected areas of the country has been provided; and (c) The public comments received [50 FR 38084, Sept. 19, 1985. Redesignated at §191.17 Effective date. The standards in this subpart shall be [50 FR 38084, Sept. 19, 1985; 50 FR 40003, Oct. Subpart C-Environmental Stand- SOURCE: 58 FR 66415, Dec. 20, 1993, unless otherwise noted. $191.21 Applicability. (a) This subpart applies to: (1) Radiation doses received by members of the public as a result of activities subject to subpart B of this part; and (2) Radioactive contamination of un- (b) This subpart does not apply to: (2) Wastes disposed of before the ef- (3) The characterizat construction, operation, any site required to be under section 113(a) of E 425, 96 Stat. 2201. § 191.22 Definitions. Unless otherwise indi subpart, all terms have th ing as in subparts A and Public water system me for the provision to the p water for human consum system has at least fiftee nections or regularly se twenty-five individuals. S cludes: (1) Any collection, trea age, and distribution fac control of the operator of and used primarily in con such system; and (2) Any collection or I storage facilities not und trol which are used prima nection with such system. Total dissolved solids mea dissolved (filterable) solids determined by use of the m fied in 40 CFR part 136. Underground source of dri means an aquifer or its por (1) Supplies any public wa or (2) Contains a sufficient ground water to supply a p system; and (i) Currently supplies drin for human consumption; or (ii) Contains fewer than 1 grams of total dissolved liter. § 191.23 General provisions. (a) Determination of compl this subpart shall be based up ground sources of drinking wa have been identified on the implementing agency determ pliance with subpart C of this (b) [Reserved] § 191.24 Disposal standards. (a) Disposal systems. (1) General. Disposal syst waste and any associated ra material shall be designed to reasonable expectation years of undisturbed performa tha disposal shall not cause the levels of radioactivity in any underground source of drinking water, in the accessible environment, to exceed the limits specified in 40 CFR part 141 as they exist on January 19, 1994. (2) Disposal systems above or within a formation which within one-quarter (1⁄4) mile contains an underground source of drinking water. [Reserved] (b) Compliance assessments need not provide complete assurance that the requirements of paragraph (a) of this section will be met. Because of the long time period involved and the nature of the processes and events of interest, there will inevitably be substantial uncertainties in projecting disposal system performance. Proof of the future performance of a disposal system is not to be had in the ordinary sense of the word in situations that deal with much shorter time frames. Instead, what is required is a reasonable expectation, on the basis of the record before the implementing agency, that compliance with paragraph (a) of this section will be achieved. $191.25 Compliance with other Federal regulations. Compliance with the provisions in this subpart does not negate the necessity to comply with any other applicable Federal regulations or requirements. § 191.26 Alternative provisions. The Administrator may, by rule, substitute for any of the provisions of this subpart alternative provisions chosen after: (a) The alternative provisions have been proposed for public comment in the FEDERAL REGISTER together with information describing the costs, risks, and benefits of disposal in accordance with the alternative provisions and the reasons why compliance with the existing provisions of this subpart appears inappropriate; (b) A public comment period of at least 90 days has been completed, during which an opportunity for public hearings in affected areas of the country has been provided; and (c) The public comments received have been fully considered in develop NOTE 1: Units of Waste. The Release Limits in Table 1 apply to the amount of wastes in any one of the following: (a) An amount of spent nuclear fuel containing 1,000 metric tons of heavy metal (MTHM) exposed to a burnup between 25,000 megawatt-days per metric ton of heavy metal (MWd/MTHM) and 40,000 MW/MTHM; (b) The high-level radioactive wastes generated from reprocessing each 1,000 MTHM exposed to a burnup between 25,000 MWd MTHM and 40,000 MWd/MTHM; (c) Each 100,000,000 curies of gamma or beta-emitting radionuclides with half-lives greater than 20 years but less than 100 years (for use as discussed in Note 5 or with materials that are identified by the Commission as high-level radioactive waste in accordance with part B of the definition of high-level waste in the NWPA); (d) Each 1,000,000 curies of other radionuclides (i.e., gamma or beta-emitters with half-lives greater than 100 years or any alpha-emitters with half-lives greater than 20 years) (for use as discussed in Note 5 or with materials that are identified by the Commission as high-level radioactive waste (e) An amount of transuranic (TRU) wastes NOTE 2: Release Limits for Specific Disposal Systems. To develop Release Limits for a particular disposal system, the quantities in Table 1 shall be adjusted for the amount of waste included in the disposal system compared to the various units of waste defined in Note 1. For example: (a) If a particular disposal system contained the high-level wastes from 50,000 MTHM, the Release Limits for that system would be the quantities in Table 1 multiplied by 50 (50,000 MTHM divided by 1,000 MTHM). (b) If a particular disposal system contained three million curies of alpha-emitting transuranic wastes, the Release Limits for that system would be the quantities in Table 1 multiplied by three (three million curies divided by one million curies). (c) If a particular disposal system contained both the high-level wastes from 50,000 MTHM and 5 million curies of alpha-emitting transuranic wastes, the Release Limits for that system would be the quantities in Table 1 multiplied by 55: NOTE 3: Adjustments for Reactor Fuels with Different Burnup. For disposal systems containing reactor fuels (or the high-level wastes from reactor fuels) exposed to an average burnup of less than 25,000 MWd/MTHM or greater than 40,000 MWd/MTHM, the units of waste defined in (a) and (b) of Note 1 shall be adjusted. The unit shall be multiplied by the ratio of 30,000 MWd/MTHM divided by the fuel's actual average burnup, except that a value of 5,000 MW/MTHM may be used when the average fuel burnup is below 5,000 Mwa MTHM and a value of 100,000 MWd/MTHM shall be used when the average fuel burnup is above 100,000 MWd/MTHM. This adjusted unit of waste shall then be used in determining the Release Limits for the disposal system. For example, if a particular disposal system contained only high-level wastes with an average burnup of 3,000 MWd/MTHM, the unit of waste for that disposal system would be: vel th If that disposal system contained the highlevel wastes from 60,000 MTHM (with an average burnup of 3,000 MWd/MTHM), then the NOTE 4: Treatment of Fract Level Wastes. In some cases, waste stream from reprocessi clear fuel may have been (or rated into two or more high-lev ponents destined for different tems. In such cases, the implen cy may allocate the Release plier (based upon the original M average fuel burnup of the hig stream) among the various disp as it chooses, provided that the Limit multiplier used for that at all of its disposal systems ma the Release Limit multiplier t used if the entire waste stream v of in one disposal system. NOTE 5: Treatment of Wastes Known Burnups or Original MT cases, the records associated wit high-level waste streams may quate to accurately determine metric tons of heavy metal in fuel that created the waste, or the average burnup that the fuel to. If the uncertainties are su original amount of heavy metal age fuel burnup for particular waste streams cannot be quar units of waste derived from (a) Note 1 shall no longer be used. I units of waste defined in (c) and 1 shall be used for such high-l streams. If the uncertainties in mation allow a range of values to ated with the original amount metal or the average fuel burnup calculations described in previous be conducted using the values tha the smallest Release Limits, exce Release Limits need not be sm those that would be calculated units of waste defined in (c) and ( 1. NOTE 6: Uses of Release Limits to Compliance with $191.13 Once rele for a particular disposal system determined in accordance with through 5, these release limits sha to determine compliance with the ments of §191.13 as follows. In case mixture of radionuclides is projec released to the accessible environn limiting values shall be determined as follows: For each radionuclide in the mixture, determine the ratio between the cumulative release quantity projected over 10,000 years and the limit for that radionuclide as determined from Table 1 and Notes 1 through 5. The sum of such ratios for all the radionuclides in the mixture may not exceed one with regard to §191.13(a)(1) and may not exceed ten with regard to § 191.13(a)(2). For example, if radionuclides A, B, and C are projected to be released in amounts Q., Qb, and Qc, and if the applicable Release Limits are RL, RLь, and RL, then the cumulative releases over 10,000 years shall be limited so that the following relationship exists: II. Effective Dose The next step is the calculation of the effective dose, E. The probability of occurrence of a stochastic effect in a tissue or organ is assumed to be proportional to the equivalent dose in the tissue or organ. The constant of proportionality differs for the various tissues of the body, but in assessing health detriment the total risk is required. This is taken into account using the tissue weighting factors, wr in Table B.2, which represent the proportion of the stochastic risk resulting from irradiation of the tissue or organ to the total risk when the whole body is irradiated uniformly and Hr is the equivalent dose in the tissue or organ, T, in the equation: The values are considered to be appropriate for protection for individuals of both sexes and all ages. 2 For purposes of calculation, the remainder is comprised of the five tissues or organs not specifically listed in Table B.2 that receive the highest dose equivalents; a weighting factor of 0.06 is applied to each of them, including the various sections of the gastrointestinal tract which are treated as separate organs. This covers all tissues and organs except the hands and forearms, the feet and ankles, the skin and the lens of the eye. The excepted tissues and organs should be excluded from the computation of HE. III. Annual Committed Tissue or Organ For internal irradiation from incorporated radionuclides, the total absorbed dose will be spread out in time, being gradually delivered as the radionuclide decays. The time distribution of the absorbed dose rate will vary with the radionuclide, its form, the mode of intake and the tissue within which it is incorporated. To take account of this distribution the quantity committed equivalent dose, Hr(t) where is the integration time in years following an intake over any particular year, is used and is the integral over time of the equivalent dose rate in a particular tissue or organ that will be received by an individual following an intake of radioactive material into the body. The time period, t, is taken as 50 years as an average time of exposure following intake: [58 FR 66415, Dec. 20, 1993] APPENDIX C TO PART 191-GUIDANCE FOR [NOTE: The supplemental information in this appendix is not an integral part of 40 CFR part 191. Therefore, the implementing agencies are not bound to follow this guidance. However, it is included because it describes the Agency's assumptions regarding the implementation of subpart B. This appendix will appear in the Code of Federal Regulations.] The Agency believes that the implementing agencies must determine compliance with §§191.13, 191.15, and 191.16 of subpart B by evaluating long-term predictions of disposal system performance. Determining compliance with § 191.13 will also involve predicting the likelihood of events and processes that may disturb the disposal system. In making these various predictions, it will be appropriate for the implementing agencies to make use of rather complex computational models, analytical theories, and prevalent expert judgment relevant to the numerical predictions. Substantial uncertainties are likely to be encountered in making these predictions. In fact, sole reliance on these numerical predictions to determine compliance may not be appropriate; the implementing agencies may choose to supplement such predictions with qualitative judgments as well. Because the procedures for determining compliance with subpart B have not been formulated and tested yet, this appendix to the rule indicates the Agency's assumptions regarding certain issues that may arise when implementing §§ 191.13, 191.15, and 191.16. Most of this guidance applies to any type of disposal system for the wastes covered by this rule. However, several sections apply only to disposal in mined geologic repositories and would be inappropriate for other types of disposal systems. Consideration of Total Disposal System. When predicting disposal system performance, the Agency assumes that reasonable projections of the protection expected from all of the engineered and natural barriers of a disposal system will be considered. Portions of the disposal system should not be disregarded, even if projected performance is uncertain, except for portions of the system that make negligible contributions to the overall isolation provided by the disposal system. Scope of Performance Assessments. Section 191.13 requires the implementing agencies to evaluate compliance through performance assessments as defined in §191.12(q). The Agency assumes that such performance assessments need not consider categories of events or processes that are estimated to have less than one chance in 10,000 of occurring over 10,000 years. Furthermore, the performance assessments need not evaluate in detail the releases from all events and processes estimated to have a greater likelihood of occurrence. Some of these events and processes may be omitted from the performance assessments if there is a reasonable expectation that the remaining probability distribution of cumulative releases would not be significantly changed by such omissions. Compliance with $191.13. The Agency assumes that, whenever practicable, the implementing agency will assemble all of the results of the performance assessments to determine compliance with §191.13 into a "complementary cumulative distribution function" that indicates the probability of exceeding various levels of cumulative release. When the uncertainties in parameters are considered in a performance assessment, the effects of the uncertainties considered can be incorporated into a single such distribution function for each disposal system considered. The Agency assumes that a disposal system can be considered to be in compliance with § 191.13 if this single distribution function meets the requirements $191.13(a). of Compliance with $$191.15 and 191.16. When the uncertainties in undisturbed performance of a disposal system are considered, the implementing agencies need not require that a very large percentage of the range of estimated radiation exposures or radionuclide concentrations fall below limits established in §§ 191.15 and 191.16, respectively. The Agen |