Article 3. Occupational Dose Limits
12VAC5-481-640. Occupational dose limits for adults.
Article 3
Occupational Dose Limits
A. The licensee shall control the occupational dose to individual adults, except for planned special exposures under 12VAC5-481-690, to the following dose limits.
1. An annual limit, which is the more limiting of:
a. The total effective dose equivalent being equal to 5 rem (0.05 Sv); or
b. 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 rem (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:
a. A lens dose equivalent of 15 rem (0.15 Sv), and
b. 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, shall be subtracted from the limits for planned special exposures that the individual may receive during the current year and during the individual's lifetime in accordance with 12VAC5-481-690 A 5.
C. When the external exposure is determined by measurement with an external personal monitoring device, the deep-dose equivalent shall be used in place of the effective dose equivalent, unless the effective dose equivalent is determined by a dosimetry method approved by the agency. The assigned deep-dose equivalent shall be for the part of the body receiving the highest exposure. The assigned shallow-dose equivalent shall 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 Appendix B to 10 CFR Part 20 and may be used to determine the individual's dose (see 12VAC5-481-1040) and to demonstrate compliance with the occupational dose limits.
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 Appendix B to 10 CFR 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 12VAC5-481-1020).
Statutory Authority
§ 32.1-229 of the Code of Virginia.
Historical Notes
Derived from Virginia Register Volume 22, Issue 25, eff. September 20, 2006; amended, Virginia Register Volume 24, Issue 18, eff. June 12, 2008; Volume 32, Issue 24, eff. August 25, 2016.
12VAC5-481-650. Compliance with requirements for summation of external and internal doses.
A. If the licensee is required to monitor under subdivisions 1 and 2 of 12VAC5-481-760, the licensee shall demonstrate compliance with the dose limits by summing external and internal doses. If the licensee is required to monitor only under subdivision 1 of 12VAC5-481-760 or only under subdivision 2 of 12VAC5-481-760, then summation is not required to demonstrate compliance with the dose limits. The licensee may demonstrate compliance with the requirements for summation of external and internal doses by meeting one of the conditions specified in subsections B, C, and D of this section. The dose equivalents for the lens of the eye, the skin, and the extremities are not included in the summation, but are subject to separate limits.
B. Intake by inhalation. If the only intake of radionuclides is by inhalation, the total effective dose equivalent limit is not exceeded if the sum of the deep-dose equivalent divided by the total effective dose equivalent limit and one of the following does not exceed unity:
1. The sum of the fractions of the inhalation ALI for each radionuclide,
2. The total number of derived air concentration-hours (DAC-hours) for all radionuclides divided by 2,000, or
3. The sum of the calculated committed effective dose equivalents to all significantly irradiated organs or tissues calculated from bioassay data using appropriate biological models and expressed as a fraction of the annual limit. For the purposes of this requirement, an organ or tissue is deemed to be significantly irradiated if, for that organ or tissue, the product of the weighting factors and the committed dose equivalent per unit intake is greater than 10% of the maximum weighted value of the committed dose equivalent per unit intake of any organ or tissue.
C. Intake by oral ingestion. If the occupationally exposed individual also receives an intake of radionuclides by oral ingestion greater than 10% of the applicable oral ALI, the licensee shall account for this intake and include it in demonstrating compliance with the limits.
D. Intake through wounds or absorption through skin. The licensee shall evaluate and to the extent practical account for intakes through wounds or skin absorption. The intake through intact skin has been included in the calculation of DAC for hydrogen-3 and does not need to be evaluated.
Statutory Authority
§ 32.1-229 of the Code of Virginia.
Historical Notes
Derived from Virginia Register Volume 22, Issue 25, eff. September 20, 2006; amended, Virginia Register Volume 24, Issue 18, eff. June 12, 2008; Volume 32, Issue 24, eff. August 25, 2016.
12VAC5-481-660. Determination of external dose from airborne radioactive material.
A. Licensees shall, when determining the dose from airborne radioactive material, include the contribution to the deep-dose equivalent, lens dose equivalent, and shallow-dose equivalent from external exposure to the radioactive cloud (see Appendix B to 10 CFR Part 20).
B. Airborne radioactive measurements and DAC values shall not be used as the primary means to assess the deep dose equivalent when the airborne radioactive materials includes radionuclides other than noble gases or if the cloud of airborne radioactive material is not relatively uniform. The determination of the deep dose equivalent to an individual shall be based upon measurements using instruments or individual monitoring devices.
Statutory Authority
§ 32.1-229 of the Code of Virginia.
Historical Notes
Derived from Virginia Register Volume 22, Issue 25, eff. September 20, 2006; amended, Virginia Register Volume 24, Issue 18, eff. June 12, 2008; Volume 32, Issue 24, eff. August 25, 2016.
12VAC5-481-670. Determination of internal exposure.
A. For purposes of assessing dose used to determine compliance with occupational dose equivalent limits, the licensee shall, when required under 12VAC5-481-760, take suitable and timely measurements of either:
1. Concentrations of radioactive materials in air in work areas;
2. Quantities of radionuclides in the body;
3. Quantities of radionuclides excreted from the body; or
4. Combinations of these measurements.
B. Unless respiratory protective equipment is used as provided in 12VAC5-481-830 or the assessment of intake is based on bioassays, the licensee shall assume that an individual inhales radioactive material at the airborne concentration in which the individual is present.
C. When specific information on the physical and biochemical properties of the radionuclides taken into the body or the behavior or the material in an individual is known, the licensee may:
1. Use that information to calculate the committed effective dose equivalent, and if used, the licensee shall document that information in the individual's record;
2. Upon prior approval from the agency, adjust the DAC or ALI values to reflect the actual physical and chemical characteristics of airborne radioactive material (e.g., aerosol size distribution or density); and
3. Separately assess the contribution of fractional intakes of Class D, W, or Y compounds of a given radionuclide (see Appendix B to 10 CFR Part 20) to the committed effective dose equivalent.
D. If the licensee chooses to assess intakes of Class Y material using the measurements given in subdivision A 2 or A 3 of this section, the licensee may delay the recording and reporting of the assessments for periods up to seven months, unless otherwise required by 12VAC5-481-1100 or 12VAC5-481-1110, in order to permit the licensee to make additional measurements basic to the assessments.
E. If the identity and concentration of each radionuclide in a mixture are known, the fraction of the DAC applicable to the mixture for use in calculating DAC-hours shall be either:
1. The sum of the ratios of the concentration to the appropriate DAC value (e.g., D, W, or Y) from Appendix B to 10 CFR Part 20 for each radionuclide in the mixture; or
2. The ratio of the total concentration for all radionuclides in the mixture to the most restrictive DAC value for any radionuclide in the mixture.
F. If the identity of each radionuclide in a mixture is known, but the concentration of one or more of the radionuclides in the mixture is not known, the DAC for the mixture shall be the most restrictive DAC of any radionuclide in the mixture.
G. When a mixture of radionuclides in air exists, licensees may disregard certain radionuclides in the mixture if:
1. The licensee uses the total activity of the mixture in demonstrating compliance with the dose limits in 12VAC5-481-640 and in complying with the monitoring requirements in 12VAC5-481-760 A 2,
2. The concentration of any radionuclide disregarded is less than 10% of its DAC, and
3. The sum of these percentages for all of the radionuclides disregarded in the mixture does not exceed 30%.
H. When determining the committed effective dose equivalent, the following information may be considered:
1. In order to calculate the committed effective dose equivalent, the licensee may assume that the inhalation of one ALI or an exposure of 2,000 DAC-hours results in a committed effective dose equivalent of 5 rem (0.05 Sv) for radionuclides that have their ALIs or DACs based on the committed effective dose equivalent.
2. When the ALI and the associated DAC is determined by the nonstochastic organ dose limit of 50 rem (0.5 Sv), the intake of radionuclides that would result in a committed effective dose equivalent of 5 rem (0.05 Sv) (the stochastic ALI) is listed in parentheses of Appendix B to 10 CFR Part 20. In this case, the licensee may, as a simplifying assumption, use the stochastic ALIs to determine committed effective dose equivalent. However, if the licensee uses the stochastic ALIs, the licensee shall also demonstrate that the limit in 12VAC5-481-640 A 1 (b) is met.
Statutory Authority
§ 32.1-229 of the Code of Virginia.
Historical Notes
Derived from Virginia Register Volume 22, Issue 25, eff. September 20, 2006; amended, Virginia Register Volume 24, Issue 18, eff. June 12, 2008; Volume 32, Issue 24, eff. August 25, 2016.
12VAC5-481-680. Determination of prior occupational dose.
A. For each individual who may enter the licensee's or registrant's restricted area and is likely to receive, in a year, an occupational dose requiring monitoring pursuant to 12VAC5-481-760, the licensee or registrant shall determine the occupational radiation dose received during the current year.
B. Prior to permitting an individual to participate in a planned special exposure, the licensee or registrant shall determine:
1. The internal and external doses from all previous planned special exposures; and
2. All doses in excess of the limits, including doses received during accidents and emergencies, received during the lifetime of the individual.
C. In complying with the requirements of subsection A or B of this section, a licensee or registrant may:
1. Accept, as a record of the occupational dose that the individual received during the current year, a written signed statement from the individual, or from the individual's most recent employer for work involving radiation exposure, that discloses the nature and the amount of any occupational dose that the individual received during the current year;
2. Accept, as the record of lifetime cumulative radiation dose, an up-to-date occupational radiation exposure form provided by the agency or equivalent, signed by the individual and countersigned by an appropriate official of the most recent employer for work involving radiation exposure, or the individual's current employer, if the individual is not employed by the licensee or registrant; and
3. Obtain reports of the individual's dose equivalent from the most recent employer for work involving radiation exposure, or the individual's current employer, if the individual is not employed by the licensee or registrant, by telephone, telegram, facsimile, or letter. The licensee or registrant shall request a written verification of the dose data if the authenticity of the transmitted report cannot be established.
D. Do the following:
1. The licensee or registrant shall record the exposure history, as required by this section on an occupational radiation exposure form provided by the agency, or other clear and legible record, of all the information required on that form. The form or record shall show each period in which the individual received occupational exposure to radiation or radioactive material and shall be signed by the individual who received the exposure. For each period for which the licensee or registrant obtains reports, the licensee or registrant shall use the dose shown in the report in preparing the occupational radiation exposure form provided by the agency or equivalent. For any period in which the licensee or registrant does not obtain a report, the licensee or registrant shall place a notation on the occupational radiation exposure form provided by the agency or equivalent indicating the periods of time for which data are not available.
2. Licensees or registrants are not required to partition historical dose between external dose equivalent(s) and internal committed dose equivalent(s). Further, occupational exposure histories obtained and recorded on the occupational radiation exposure form provided by the agency or equivalent before September 20, 2006, might not have included effective dose equivalent, but may be used in the absence of specific information on the intake of radionuclides by the individual.
E. If the licensee or registrant is unable to obtain a complete record of an individual's current and previously accumulated occupational dose, the licensee or registrant shall assume:
1. In establishing administrative controls pursuant to 12VAC5-481-640 for the current year, that the allowable dose limit for the individual is reduced by 12.5 mSv (1.25 rem) for each quarter for which records were unavailable and the individual was engaged in activities that could have resulted in occupational radiation exposure; and
2. That the individual is not available for planned special exposures.
F. The licensee or registrant shall retain the records on an occupational radiation exposure form provided by the agency or equivalent until the agency terminates each pertinent license or registration requiring this record. The licensee or registrant shall retain records used in preparing the occupational radiation exposure form provided by the agency or equivalent for three years after the record is made.
Statutory Authority
§ 32.1-229 of the Code of Virginia.
Historical Notes
Derived from Virginia Register Volume 22, Issue 25, eff. September 20, 2006; amended, Virginia Register Volume 24, Issue 18, eff. June 12, 2008.
12VAC5-481-690. Planned special exposures.
A licensee may authorize an adult worker to receive doses in addition to and accounted for separately from the doses received under the limits specified in 12VAC5-481-640 provided that each of the following conditions is satisfied:
1. The licensee authorizes a planned special exposure only in an exceptional situation when alternatives that might avoid the dose estimated to result from the planned special exposure are unavailable or impractical.
2. The licensee, and employer if the employer is not the licensee, specifically authorizes the planned special exposure in writing before the exposure occurs.
3. Before a planned special exposure, the licensee ensures that each individual involved is:
a. Informed of the purpose of the planned operation;
b. Informed of the estimated doses and associated potential risks and specific radiation levels or other conditions that might be involved in performing the task; and
c. Instructed in the measure to be taken to keep the dose ALARA considering other risks that may be present.
4. Prior to permitting an individual to participate in a planned special exposure, the licensee ascertains prior doses as required by 12VAC5-481-1020 during the lifetime of the individual for each individual involved.
5. Subject to 12VAC5-481-640 A 2, the licensee does not authorize a planned special exposure that would cause an individual to receive a dose from all planned special exposures and all doses in excess of the limits to exceed:
a. The numerical values of any of the dose limits in 12VAC5-481-640 A 1 in any year; and
b. Five times the annual dose limits in 12VAC5-481-640 A 1 during the individual's lifetime.
6. The licensee maintains records of the conduct of a planned special exposure in accordance with 12VAC5-481-1030 and submits a written report in accordance with 12VAC5-481-1120.
7. The licensee records the best estimate of the dose resulting from the planned special exposure in the individual's record and informs the individual in writing of the dose within 30 days from the date of the planned special exposure. The dose from planned special exposures is not be considered in controlling future occupational dose limits of the individual under 12VAC5-481-640 A 1 but is to be included in evaluations required by subdivisions 4 and 5 of this section.
Statutory Authority
§ 32.1-229 of the Code of Virginia.
Historical Notes
Derived from Virginia Register Volume 22, Issue 25, eff. September 20, 2006; amended, Virginia Register Volume 24, Issue 18, eff. June 12, 2008; Volume 32, Issue 24, eff. August 25, 2016.
12VAC5-481-700. Occupational dose limits for minors.
The annual occupational dose limits for minors are 10% of the annual dose limits specified for adult workers in 12VAC5-481-640.
Statutory Authority
§ 32.1-229 of the Code of Virginia.
Historical Notes
Derived from Virginia Register Volume 22, Issue 25, eff. September 20, 2006; amended, Virginia Register Volume 24, Issue 18, eff. June 12, 2008; Volume 32, Issue 24, eff. August 25, 2016.
12VAC5-481-710. Dose to an embryo/fetus.
A. The licensee shall ensure that the dose equivalent to the embryo/fetus during the entire pregnancy due to occupational exposure of a declared pregnant woman does not exceed 500 millirem (5 mSv).
B. The licensee shall make efforts to avoid substantial variation above a uniform monthly exposure rate to a declared pregnant woman so as to satisfy the limits in subsection A of this section.
C. The dose equivalent to the embryo/fetus is the sum of:
1. The deep dose equivalent to the declared pregnant woman; and
2. The dose equivalent to the embryo/fetus resulting from radionuclides in the embryo/fetus and radionuclides in the declared pregnant woman.
D. If the dose equivalent to the embryo/fetus is found to have exceeded 500 millirem (5 mSv), or is within 50 millirem (0.5 mSv) of this dose, by the time the woman declares the pregnancy to the licensee, the licensee shall be deemed to be in compliance with subsection A of this section if the additional dose equivalent to the embryo/fetus does not exceed 50 millirem (0.5 mSv) during the remainder of the pregnancy.
Statutory Authority
§ 32.1-229 of the Code of Virginia.
Historical Notes
Derived from Virginia Register Volume 22, Issue 25, eff. September 20, 2006; amended, Virginia Register Volume 24, Issue 18, eff. June 12, 2008; Volume 32, Issue 24, eff. August 25, 2016.