Effective Date: 01/08/1997
Title: Section 16.6 - Occupational dose limits

16.6 Occupational dose limits.

(a) Occupational dose limits for adults.

(1) Except for planned special exposures pursuant to subdivision 16.6(f), no person shall transfer, receive, possess or use any radiation source so as to cause any individual adult to receive an occupational dose from all sources of radiation that exceeds any of the following limits:

(i) The annual limit, which is the more limiting of:

(a) The total effective dose equivalent being equal to 0.05 Sv (5 rem); 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 0.50 Sv (50 rem).

(ii) The annual limits to the lens of the eye, to the skin, and to the extremities which are:

(a) An eye dose equivalent of 0.15 Sv (15 rem), and

(b) A shallow dose equivalent of 0.50 Sv (50 rem) to the skin or to any extremity.

(2) 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 and during the individual's lifetime. (See paragraph (6) of subdivision (f) of this section).

(3) The assigned deep dose equivalent and shallow dose equivalent shall be for the portion of the body receiving the highest exposure determined as follows:

(i) The deep dose equivalent, eye 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.

(ii) When a protective apron is worn pursuant to paragraph (3) of section 16.58(b) by physicians during x-ray fluoroscopic procedures and monitoring is conducted as specified in paragraph (1) of section 16.11(b), the effective dose equivalent for external radiation may be determined for these individuals as follows:

(a) When only one individual monitoring device is used and it is located at the neck outside the protective apron, the reported deep dose equivalent value multiplied by 0.3 shall be the effective dose equivalent for external radiation; or

(b) When individual monitoring devices are worn, both under the protective apron at the waist and outside the protective apron at the neck, the effective dose equivalent for external radiation shall be assigned the value of the sum of the deep dose equivalent reported for the individual monitoring device located at the waist under the protective apron multiplied by 1.5 and the deep dose equivalent reported for the individual monitoring device located at the neck outside the protective apron multiplied by 0.04.

(4) Derived air concentration (DAC) and annual limit on intake (ALI) values are presented in Appendix 16-C, Table 1, infra, and may be used to determine the individual's dose and to demonstrate compliance with the occupational dose limits.

(5) Notwithstanding the annual dose limits, the licensee shall limit the soluble uranium intake by an individual to 10 milligrams in a week. (See Footnote 3 of Appendix 16-C.)

(6) The licensee or registrant 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 section 16.6(e).)

(b) Compliance with requirements for summation of external and internal dose.

(1) If the licensee or registrant is required to monitor pursuant to both subdivisions (a) and (d) of section 16.11, the licensee or registrant shall demonstrate compliance with the dose limits by summing external and internal doses. If the licensee or registrant is required to monitor only pursuant to subdivision 16.11(a) or only pursuant to subdivision 16.11(d), then summation is not required to demonstrate compliance with the dose limits. The licensee or registrant may demonstrate compliance with the requirements for summation of external and internal doses by meeting one of the conditions specified in paragragh (2), and the conditions in paragraphs (3) and (4) of this subdivision. 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.

(2) 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: (i) The sum of the fractions of the inhalation ALI for each radionuclide, or

(ii) The total number of derived air concentrations-hours (DAC-hours) for all radionuclides divided by 2,000, or

(iii) The sum of the calculated committed effective dose equivalents to all significantly irradiated organs or tissues (T) calculated from bioassay data using appropriate biological models and expressed as a fraction of the annual limit. For 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, W(t), and the committed dose equivalent, H(t)(50), per unit intake is greater than 10 percent of the maximum weighted value of H(50), that is, W(t) H(t)(50) per unit intake for any organ or tissue.

(3) Intake by oral ingestion. If the occupationally exposed individual also receives an intake of radionuclides by oral ingestion greater than 10 percent of the applicable oral ALI, the licensee or registrant shall account for this intake and include it in demonstrating compliance with the limits.

(4) Intake through wounds or absorption through skin. The licensee or registrant shall evaluate and 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 or accounted for pursuant to this paragraph.

(c) Determination of external dose from airborne radioactive material.

(1) Licensees shall, when determining the dose from airborne radioactive material, include the contribution to the deep dose equivalent, eye dose equivalent, and shallow does equivalent from external exposure to the radioactive cloud (See Appendix 16-C, Footnotes 1 and 2).

(2) Airborne radioactivity measurements and DAC values shall not be used as the primary means to assess the deep dose equivalent when the airborne radioactive material 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.

(d) Determination of internal exposure.

(1) For purposes of assessing dose used to determine compliance with occupational dose equivalent limits, the licensee shall, when required under section 16.11, take any of the following measurements as may be necessary for timely and appropriate detection and assessment of intake of radioactivity by individuals:

(i) Concentrations of radioactive materials in air in work areas; or

(ii) Quantities of radionuclides in the body; or

(iii) Quantities of radionuclides excreted from the body; or

(iv) Combinations of these measurements.

(2) Unless respiratory protective equipment is used, as provided in section 16.26, or the assessment of intake is based on bioassays, the licensee or registrant shall assume that an individual inhales radioactive material at the airborne concentration in which the individual is present.

(3) When specific information on the physical and biochemical properties of the radionuclides taken into the body or the behavior of the material in an individual is known, the licensee or registrant may:

(i) Use that information to calculate the committed effective dose equivalent, and, if used, the licensee or registrant shall document that information in the individual's record; and
(ii) Upon prior approval of the Department, adjust the DAC or ALI values to reflect the actual physical and chemical characteristics of airborne radioactive material, for example, aerosol size distribution or density; and

(iii) Separately assess the contribution of fractional intakes of Class D, W, or Y compounds of a given radionuclide to the committed effective dose equivalent.

(4) If the licensee chooses to assess intakes of Class Y material using the measurements given in subparagraphs (ii) or (iii) of paragraph (1) of section 16.6(d), the licensee or registrant may delay the recording and reporting of the assessments for periods up to 7 months, unless otherwise required by sections 16.15(b) or 16.15(c). This delay permits the licensee or registrant to make additional measurements basic to the assessments.

(5) 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:

(i) The sum of the ratios of the concentration to the appropriate DAC value, that is, D, W, or Y, from Appendix 16-C, for each radionuclide in the mixture; or

(ii) The ratio of the total concentration for all radionuclides in the mixture to the most restrictive DAC value for any radionuclide in the mixture. (6) 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.

(7) When a mixture of radionuclides in air exists, a licensee may disregard certain radionuclides in the mixture if:

(i) The licensee uses the total activity of the mixture in demonstrating compliance with the dose limits in section 16.6(a) and in complying with the monitoring requirements in section 16.11(d), and

(ii) The concentration of any radionuclide disregarded is less than 10 percent of its DAC, and

(iii) The sum of these percentages for all of the radionuclides disregarded in the mixture does not exceed 30 percent.

(8) When determining the committed effective dose equivalent, the following information may be considered:

(i) In order to calculate the committed effective dose equivalent, the licensee or registrant may assume that the inhalation of one ALI, or an exposure of 2,000 DAC-hours, results in a committed effective dose equivalent of 0.05 Sv (5 rem) for radionuclides that have their ALIs or DACs based on the committed effective dose equivalent.

(ii) For an ALI and the associated DAC determined by the nonstochastic organ dose limit of 0.50 Sv (50 rem), the intake of radionuclides that would result in a committed effective dose equivalent of 0.05 Sv (5 rem), that is, the stochastic ALI, is listed in parentheses in Appendix 16-C, Table 1, infra. The licensee or registrant may, as a simplifying assumption, use the stochastic ALIs to determine committed effective dose equivalent. However, if the licensee or registrant uses the stochastic ALIs, the licensee or registrant shall also demonstrate that the limit in section 16.6(a)(1)(i)(b) is met.

(e) Determination of prior occupational dose.

(1) 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 section 16.11, the licensee or registrant shall:

(i) Determine the occupational radiation dose received during the current year; and

(ii) Request in writing the records of lifetime cumulative occupational radiation dose.

(2) Prior to permitting an individual to participate in a planned special exposure, the licensee or registrant shall determine:

(i) The internal and external doses from all previous planned special exposures; and

(ii) All doses in excess of the limits, including doses received during accidents and emergencies, received during the lifetime of the individual.

(3) In complying with the requirements of paragraph (1) of this subdivision, a licensee or registrant may:

(i) 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; and

(ii) Accept, as the record of lifetime cumulative radiation dose, an up-to-date Department Form "Cumulative Occupational Radiation Exposure History", 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

(iii) 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.

(4) The licensee or registrant shall record the exposure history, as required by paragraph (1) of this subdivision, on Department Form "Cumulative Occupational Radiation Exposure History", or other clear and legible record, of all the information required on that form.

(i) 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 Department Form "Cumulative Occupational Radiation Exposure History". For any period in which the licensee or registrant does not obtain a report, the licensee or registrant shall place a notation on Department Form "Cumulative Occupational Radiation Exposure History" indicating the periods of time for which data are not available. (ii) Licensees or registrants are not required to reevaluate the separate external dose equivalents and internal committed dose equivalent s or intakes of radionuclides assessed under the regulations in this Part in effect before the effective date of these regulations. Further occupational exposure histories obtained and recorded on Department Form "Cumulative Occupational Radiation Exposure History" before the effective date of these regulations, would not have included effective dose equivalent, but may be used in the absence of specific information on the intake of radionuclides by the individual.

(5) If the licensee or registrant is unable to obtain complete records of an individual's current and previously accumulated occupational dose, the licensee or registrant:

(i) When establishing administrative controls under paragraph (6) of section 16.6(a) for the current year, shall assume 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

(ii) Shall not authorize the individual to receive any planned special exposures.

(6) The licensee or registrant shall retain the records on Department Form "Cumulative Occupational Radiation Exposure History" or equivalent until the Department authorizes their disposition. The licensee or registrant shall retain records used in preparing Department Form "Cumulative Occupational Radiation Exposure History" for 3 years after the record is made.

(f) Planned special exposures. A licensee or registrant may authorize an adult worker to receive doses in addition to and accounted for separately from the doses received under the limits specified in section 16.6(a) provided that each of the following conditions is satisfied:

(1) The licensee or registrant authorizes the planned special exposure only in an exceptional situation when alternatives that might avoid the
higher exposure are unavailable or impractical.

(2) The licensee or registrant, and employer if the employer is not the licensee or registrant, specifically authorizes the planned special exposure, in writing, before the exposure occurs.

(3) Before a planned special exposure, the licensee or registrant ensures that each worker involved is:

(i) Informed of the purpose of the planned operation; and

(ii) 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

(iii) Instructed in the measures 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 or registrant ascertains prior doses as required by paragraph (2) of section 16.6(e).

(5) Subject to paragraph (2) of section 16.6(a), the licensee or registrant shall 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:

(i) The numerical values of any of the dose limits in paragraph (1) of section 16.6(a) in any year; and

(ii) Five times the annual dose limits in paragraph (1) of section 16.6(a) during the individual's lifetime.

(6) The licensee or registrant maintains records of the conduct of a planned special exposure in accordance with section 16.14(e) and submits a written report in accordance with section 16.15(d).

(7) The licensee or registrant 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 shall not be considered in controlling future occupational dose of the individual pursuant to paragraph (1) of section 16.6(a) but shall be included in evaluations required by paragraphs (4) and (5) of this subdivision.

(g) Occupational dose limits for minors. The annual occupational dose limits for minors are 10 percent of the annual occupational dose limits specified for adult workers in section 16.6(a).

(h) Dose to an embryo/fetus.

(1) The licensee or registrant shall ensure that the dose to an embryo/fetus during the entire pregnancy, due to occupational exposure of a declared pregnant woman, does not exceed 5 mSv (0.5 rem). (See section 16.14(f) for recordkeeping requirements).

(2) The licensee or registrant shall review past exposure history and adjust working conditions so as to avoid a monthly total effective dose equivalent of more than 50 mrem to the embryo/fetus of a declared pregnant woman. (3) The dose to an embryo/fetus shall be taken as the sum of:

(i) The deep dose equivalent to the declared pregnant woman during the entire pregnancy period; and

(ii) The dose to the embryo/fetus from radionuclides in the embryo/fetus and radionuclides in the declared pregnant woman during the entire pregnancy period.

(4) If by the time the woman declares pregnancy to the licensee or registrant, the dose to the embryo/fetus exceeded 4.5 mSv (0.45 rem), the licensee or registrant shall be deemed to be in compliance with paragraph (1) of this subdivision if the additional dose to the embryo/fetus does not exceed 0.50 mSv (0.05 rem) during the remainder of the pregnancy.




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