(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 MWd/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 in accordance with part B of the definition of high-level waste in the NWPA); or
(e) An amount of transuranic (TRU) wastes containing one million curies of alpha-emitting transuranic radionuclides with half-lives greater than 20 years.
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 MWd/MTHM may be used when the average fuel burnup is below 5,000 MWd/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:
If that disposal system contained the high-level wastes from 60,000 MTHM (with an average burnup of 3,000 MWd/MTHM), then the Release Limits for that system would be the quantities in Table 1 multiplied by ten:
which is the same as:
Note 4: Treatment of Fractionated High-Level Wastes. In some cases, a high-level waste stream from reprocessing spent nuclear fuel may have been (or will be) separated into two or more high-level waste components destined for different disposal systems. In such cases, the implementing agency may allocate the Release Limit multiplier (based upon the original MTHM and the average fuel burnup of the high-level waste stream) among the various disposal systems as it chooses, provided that the total Release Limit multiplier used for that waste stream at all of its disposal systems may not exceed the Release Limit multiplier that would be used if the entire waste stream were disposed of in one disposal system.
Note 5: Treatment of Wastes with Poorly Known Burnups or Original MTHM. In some cases, the records associated with particular high-level waste streams may not be adequate to accurately determine the original metric tons of heavy metal in the reactor fuel that created the waste, or to determine the average burnup that the fuel was exposed to. If the uncertainties are such that the original amount of heavy metal or the average fuel burnup for particular high-level waste streams cannot be quantified, the units of waste derived from (a) and (b) of Note 1 shall no longer be used. Instead, the units of waste defined in (c) and (d) of Note 1 shall be used for such high-level waste streams. If the uncertainties in such information allow a range of values to be associated with the original amount of heavy metal or the average fuel burnup, then the calculations described in previous Notes will be conducted using the values that result in the smallest Release Limits, except that the Release Limits need not be smaller than those that would be calculated using the units of waste defined in (c) and (d) of Note 1.
Note 6: Uses of Release Limits to Determine Compliance with §191.13 Once release limits for a particular disposal system have been determined in accordance with Notes 1 through 5, these release limits shall be used to determine compliance with the requirements of §191.13 as follows. In cases where a mixture of radionuclides is projected to be released to the accessible environment, the 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 Qa, Qb, and Qc, and if the applicable Release Limits are RLa, RLb, and RLc, then the cumulative releases over 10,000 years shall be limited so that the following relationship exists:
[50 FR 38084, Sept. 19, 1985, as amended at 58 FR 66415, Dec. 20, 1993]
Appendix B to Part 191—Calculation of Annual Committed Effective Dose
I. Equivalent Dose
The calculation of the committed effective dose (CED) begins with the determination of the equivalent dose, HT, to a tissue or organ, T, listed in Table B.2 below by using the equation:
where DT,Ris the absorbed dose in rads (one gray, an SI unit, equals 100 rads) averaged over the tissue or organ, T, due to radiation type, R, and wRis the radiation weighting factor which is given in Table B.1 below. The unit of equivalent dose is the rem (sievert, in SI units).
Table B.1—Radiation Weighting Factors, wR1
|Radiation type and energy range2||wRvalue|
|Photons, all energies||1|
|Electrons and muons, all energies||1|
|Neutrons, energy < 10 keV||5|
|10 keV to 100 keV||10|
|>100 keV to 2 MeV||20|
|>2 MeV to 20 MeV||10|
|Protons, other than recoil protons, >2 MeV||5|
|Alpha particles, fission fragments, heavy nuclei||20|
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, wTin 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 HTis the equivalent dose in the tissue or organ, T, in the equation:
Table B.2—Tissue Weighting Factors, wT1
|Tissue or organ||wTvalue|
|Red bone marrow||0.12|
III. Annual Committed Tissue or Organ Equivalent Dose
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, HΤ(τ) 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, τ, is taken as 50 years as an average time of exposure following intake:
for a single intake of activity at time t0where HT(t) is the relevant equivalent-dose rate in a tissue or organ at time t. For the purposes of this part, the previously mentioned single intake may be considered to be an annual intake.
IV. Annual Committed Effective Dose
If the committed equivalent doses to the individual tissues or organs resulting from an annual intake are multiplied by the appropriate weighting factors, wT, and then summed, the result will be the annual committed effective dose, E(τ):
[58 FR 66415, Dec. 20, 1993]
Source: 56 FR 23396, May 21, 1991, unless otherwise noted.
§ 20.1201 Occupational dose limits for adults.
(a) The licensee shall control the occupational dose to individual adults, except for planned special exposures under
§ 20.1206, to the following dose limits.
(1) An annual limit, which is the more limiting of--
(i) The total effective dose equivalent being equal to 5 rems (0.05 Sv); or
(ii) The sum of the deep-dose equivalent and the committed dose equivalent to any individual organ or tissue other than the
lens of the eye being equal to 50 rems (0.5 Sv).
(2) The annual limits to the lens of the eye, to the skin of the whole body,
and to the skin of the extremities, which are:
(i) A lens dose equivalent of 15 rems (0.15 Sv), and
(ii) A shallow-dose equivalent of 50 rem (0.5 Sv) to the skin of the whole
body or to the skin of any extremity.
(b) Doses received in excess of the annual limits, including doses received during accidents, emergencies, and planned
special exposures, must be subtracted from the limits for planned special exposures that the individual may receive during
the current year (see § 20.1206(e)(1)) and during the individual's lifetime (see § 20.1206(e)(2)).
(c) When the external exposure is determined by measurement with an external personal monitoring device, the deep-dose equivalent must be used in place of the effective dose equivalent, unless the effective dose equivalent is determined by a dosimetry method approved by the NRC. The assigned deep-dose equivalent must be for the part of the body receiving the highest exposure. The assigned shallow-dose equivalent must be the dose averaged over the contiguous 10 square centimeters of skin receiving the highest exposure. The deep-dose equivalent, lens-dose equivalent, and shallow-dose equivalent may be assessed from surveys or other radiation measurements for the purpose of demonstrating compliance with the occupational dose limits, if the individual monitoring device was not in the region of highest potential exposure, or the results of individual monitoring are unavailable.
(d) Derived air concentration (DAC) and annual limit on intake (ALI) values are presented in table 1 of appendix B to part
20 and may be used to determine the individual's dose (see § 20.2106) and to demonstrate compliance with the occupational
(e) In addition to the annual dose limits, the licensee shall limit the soluble uranium intake by an individual to 10
milligrams in a week in consideration of chemical toxicity (see footnote 3 of appendix B to part 20).
(f) The licensee shall reduce the dose that an individual may be allowed to receive in the current year by the amount of
occupational dose received while employed by any other person (see § 20.2104(e)).
Code of Federal Regulations (10 CFR)
Part 20 "Standards for protection against radiation",
version: 15 July 2014.
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