Section 157.22. Occupational dose limits.

 

(1)   Occupational dose limits for adults.

(a) A licensee or registrant shall control the occupational dose to individual adults, except for planned special exposures under sub. (6) , to the following dose limits:

1. An annual limit, which is the more limiting of either of the following:

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

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 0.5 Sv (50 rem).

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 0.15 Sv (15 rem).

b. A shallow dose equivalent of 0.5 Sv (50 rem) 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.

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

1. 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 method approved by the department. 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.

2. When a protective apron is worn while working with medical fluoroscopic equipment and monitoring is conducted as specified in s. DHS 157.25 (2) (a) 5. , the effective dose equivalent for external radiation shall be determined as follows:

a. When only one individual monitoring device is used and it is located at the neck outside the protective apron, and the exposure is less than 25% of any limit specified in par. (a) , the reported deep dose equivalent shall be the effective dose equivalent for external radiation.

b. When only one individual monitoring device is used and it is located at the neck outside the apron and the exposure is greater than 25% of the any limit specified in par. (a) , the effective dose equivalent shall be the deep dose equivalent multiplied by 0.3.

c. If a protective apron is worn, the individual monitoring device shall be located at the neck, which is, collar. If a second monitoring device is used, for the same purpose, it shall be located under the protective apron at the waist. The estimated effective dose equivalent ( H E ) when wearing 2 monitoring devices, one located outside and one under a protective apron, shall be calculated using the following formula: H E (estimate) = 1.5 H W + 0.04 H N where H W = badge reading from the waist badge under the apron and H N = badge reading from the neck badge worn outside the apron.

(d) Derived air concentration and annual limit on intake values are specified in Table I of Appendix E and may be used to determine the individual's dose and to demonstrate compliance with the occupational dose limits.

(e) In addition to the annual dose limits, a licensee or registrant shall limit the soluble uranium intake by an individual to 10 milligrams in a week in consideration of chemical toxicity.

(f) A 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 during the current year.

(2)   Compliance with requirements for summation of external and internal doses.

(a) If a licensee or registrant is required to monitor under both s. DHS 157.25 (2) (a) and (b) , a licensee or registrant shall demonstrate compliance with the dose limits by summing external and internal doses. If a licensee or registrant is required to monitor only under s. DHS 157.25 (2) (a) or (b) , then summation is not required to demonstrate compliance with the dose limits. A licensee or registrant may demonstrate compliance with the requirements for summation of external and internal doses by meeting one of the conditions in par. (b) and the conditions of pars. (c) and (d) . 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) 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 any 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 for all radionuclides divided by 2,000.

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 purposes of this subdivision, 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% of the maximum weighted value of H T,50 , that is, w T H T,50 , per unit intake for any organ or tissue.

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

(d) A licensee or registrant 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 or taken into account.

(3)   Determination of external doses from airborne radioactive material.

(a) A licensee or registrant shall, when determining the dose from airborne radioactive material, include the contribution to the deep dose equivalent, eye dose equivalent, and shallow dose equivalent from external exposure to the radioactive cloud.

(b) Airborne radioactivity measurements and DAC values may 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 in its distribution of radioactive material in the cloud. The determination of the deep dose equivalent to an individual shall be based upon measurements using instruments or individual monitoring devices.

(4)   Determination of internal exposure.

(a) For purposes of assessing dose used to determine compliance with occupational dose equivalent limits, a licensee or registrant shall, when required under s. DHS 157.25 (2) , take suitable and timely measurements of all of the following:

1. Concentrations of airborne radioactive materials in work areas.

2. Quantities of radionuclides in the body.

3. Quantities of radionuclides excreted from the body.

4. Combinations of the measurements in subds. 1. to 3.

(b) Unless respiratory protective equipment is used, as provided in s. DHS 157.27 (3) , or the assessment of intake is based on bioassays, a licensee or registrant shall assume that an individual inhales radioactive material at the airborne concentration in which the individual is present.

(c) When the physical and biochemical properties of the radionuclides taken into the body or the behavior of the material in an individual is known, a licensee or registrant may do any of the following:

1. 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.

2. 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.

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

(d) If a licensee or registrant chooses to assess intakes of Class Y material using the measurements given in par. (a) 2. or 3. , a licensee or registrant may delay the recording and reporting of the assessments for periods up to 7 months, unless otherwise required by s. DHS 157.32 (2) or (3) .

(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 of the following:

1. The sum of the ratios of the concentration to the appropriate DAC value, that is, D, W or Y, from Appendix E for each radionuclide in the mixture.

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, a licensee or registrant may disregard certain radionuclides in the mixture if all of the following apply:

1. The licensee or registrant uses the total activity of the mixture in demonstrating compliance with the dose limits in s. DHS 157.22 (1) and in complying with the monitoring requirements in s. DHS 157.25 (2) (b) .

2. The concentration of any radionuclide disregarded is less than 10% of its DAC.

3. The sum of the percentages under subds. 1. and 2. 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. 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.

2. For an ALI and the associated DAC determined by the nonstochastic organ dose limit of 0.5 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 Table I of Appendix E. The licensee or registrant may, as a simplifying assumption, use the stochastic ALI to determine committed effective dose equivalent. However, if the licensee or registrant uses the stochastic ALI, the licensee or registrant shall also demonstrate that the limit in s. DHS 157.22 (1) (a) 1. b. is met.

(5)   Determination of prior occupational dose.

(a) For each individual who may enter a licensee's or registrant's restricted area and is likely to receive, in a year, an occupational dose requiring monitoring under s. DHS 157.25 (2) , a licensee or registrant shall determine the occupational radiation dose received during the current year.

(b) Before an individual may participate in a planned special exposure, a licensee or registrant shall determine all of the following:

1. The internal and external doses from all previous planned special exposures.

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 par. (a) , a licensee or registrant may use either of the following means:

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. Obtain, by telephone, facsimile, electronic media or letter, 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. A licensee or registrant shall request a written verification of the dose data if the authenticity of the transmitted report cannot be established.

(d)

1. A licensee or registrant shall record the exposure history, as required by par. (a) , on a occupational radiation exposure form provided by the department, 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 a licensee or registrant obtains reports, a licensee or registrant shall use the dose shown in the report in preparing the occupational radiation exposure form or equivalent. For any period in which a licensee or registrant does not obtain a report, a licensee or registrant shall place a notation on the occupational radiation exposure form or equivalent indicating the periods of time for which data are not available.

2. A licensee or registrant is not required to partition historical dose between external dose equivalents and internal committed dose equivalents. Further, occupational exposure histories obtained and recorded on the department's occupational radiation exposure form or equivalent before the effective date of August 1, 2002, may 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 a licensee or registrant is unable to obtain a complete record of an individual's current and previously accumulated occupational dose, a licensee or registrant shall assume all the following:

1. In establishing administrative controls under sub. (1) (f) 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.

2. That the individual is not available for planned special exposures.

(f) A licensee or registrant shall retain the records on the department's occupational radiation exposure form or equivalent until the department terminates each pertinent license or registration requiring this record. A licensee or registrant shall retain records used in preparing the occupational radiation exposure form or equivalent for 3 years after the record is made.

(6)   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 sub. (1) provided that each of the following conditions is satisfied:

(a) A licensee or registrant 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.

(b) A 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.

(c) Before a planned special exposure, a licensee or registrant ensures that each individual involved has been informed and instructed in all the following:

1. The purpose of the planned operation.

2. The estimated doses and associated potential risks and specific radiation levels or other conditions that might be involved in performing the task.

3. The measures to be taken to keep the dose ALARA considering other risks that may be present.

(d) Prior to permitting an individual to participate in a planned special exposure, a licensee or registrant ascertains prior doses as required by sub. (5) (b) during the lifetime of the individual for each individual involved.

(e) Subject to sub. (1) (b) , a licensee or registrant may 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 any of the following limits:

1. The numerical values of any of the dose limits in sub. (1) (a) in any year.

2. Five times the annual dose limits in sub. (1) (a) during the individual's lifetime.

(f) A licensee or registrant maintains records of the conduct of a planned special exposure under s. DHS 157.31 (6) and submits a written report under s. DHS 157.32 (4) .

(g) A 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 may not be considered in controlling future occupational dose of the individual under sub. (1) (a) but shall be included in evaluations required by pars. (d) and (e) .

(7)   Occupational dose limit for a minor.

(a) The annual occupational dose limit for a minor is 10% of the annual occupational dose limits specified for adult workers in sub. (1) .

(b) A minor may not work in an area where the minor could receive a deep dose equivalent in excess of .02 mSv (2 mrem) in any one hour unless authorized in writing by the department.

(8)   Dose equivalent to an embryo or fetus.

(a) A licensee or registrant shall ensure that the dose equivalent to an embryo or fetus during the entire pregnancy, due to occupational exposure of a declared pregnant woman, does not exceed 5 mSv (500 mrem).

(b) A licensee or registrant shall make efforts to avoid substantial variation above a uniform monthly exposure rate to a declared pregnant woman so as to satisfy the limit in par. (a) .

(c) The dose equivalent to an embryo or fetus is the sum of all of the following:

1. The deep dose equivalent to the declared pregnant women.

2. The dose equivalent to the embryo or fetus resulting from radionuclides in the embryo or fetus and radionuclides in the declared pregnant woman.

(d) If the dose equivalent to the embryo or fetus is found to have exceeded 5 mSv (500 mrem), or is within 0.5 mSv (50 mrem) of this dose, by the time the woman declares the pregnancy to a licensee or registrant, a licensee or registrant shall be deemed to be in compliance with par. (a) if the additional dose equivalent to the embryo or fetus does not exceed 0.5 mSv (50 mrem) during the remainder of the pregnancy.

CR 01-108 : cr. Register July 2002 No. 559 , eff. 8-1-02; CR 06-021 : am. (1) (a) 2. (intro.), b., and (8) (c) (intro.), r. and recr. (1) (c) 1., Register October 2006 No. 610 , eff. 11-1-06; CR 09-062 : am. (1) (c) 1. Register April 2010 No. 652 , eff. 5-1-10.

Note

See s. DHS 157.31 (7) for instructions about recording the exposure levels. Microsoft Windows NT 6.1.7601 Service Pack 1 See footnote c / of Appendix E for the calculation method for determining DAC for soluable mixtures of uranium. Microsoft Windows NT 6.1.7601 Service Pack 1 See sub. (5) for instruction on determining occupational dose. Microsoft Windows NT 6.1.7601 Service Pack 1 See Appendix E, footnotes a / and b / for methods used for calculating dose from exposure to a radioactive cloud for materials that have a half-life of less than 2 hours. Microsoft Windows NT 6.1.7601 Service Pack 1 See Appendix E for a description of the pulmonary clearance times of the compounds involved in the exposure. Microsoft Windows NT 6.1.7601 Service Pack 1 The delay permits the licensee or registrant to make additional measurements basic to the assessments. Microsoft Windows NT 6.1.7601 Service Pack 1 An occupational radiation exposure history form may be obtained by writing to: Department of Health Services, Radiation Protection Section, P.O. Box 2659, Madison WI 53701-2659; or by downloading the form from the Department website at: http://dhs.wisconsin.gov/radiation/Index.htm . Microsoft Windows NT 6.1.7601 Service Pack 1 The Department's occupational radiation exposure history form may be obtained by writing to: Department of Health Services, Radiation Protection Section, P.O. Box 2659, Madison WI 53701-2659; or by downloading the form from the Department website at: http://dhs.wisconsin.gov/radiation/Index.htm . Microsoft Windows NT 6.1.7601 Service Pack 1 See DHS 157.31 (7) for record keeping requirements. Microsoft Windows NT 6.1.7601 Service Pack 1 The National Council on Radiation Protection and Measurements recommended in NCRP Report No. 91, "Recommendations on Limits for Exposure to Ionizing Radiation," June, 1, 1987, that no more than 0.5 mSv (50 mrem) to the embryo or fetus be received in any one month. Microsoft Windows NT 6.1.7601 Service Pack 1