ML090770221

(Draft Issued as DG-8010), Monitoring Criteria & Methods to Calculate Occupational Radiation Doses

ML090770221
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Issue date:	07/31/1992
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RG-8.34
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U.S. NUCLEAR REGULATORY COMMISSION REGULATORY (

OFFICE OF NUCLEAR REGULATORY RESEARCH REGULATORY GUIDE 8.34 (Draft was issued as DG-8010)

MONITORING CRITERIA AND METHODS TO CALCULATE OCCUPATIONAL RADIATION DOSES July 1992 0UIDE A. INTRODUCTION Monitoring of an individual's external radiation exposure is required by 10 CFR 20.1502(a) if the ex-ternal occupational dose is likely to exceed 10% of the dose limit appropriate for the individual (i.e.,

adult, minor, or declared pregnant woman). External radiation monitoring is also required by 10 CFR 20.1502(a)(3) for any individual entering a high or very high radiation area.

Monitoring of the intake of radioactive material is required by 10 CFR 20.1502(b) if the intake is likely to exceed 0. 1 ALI (annual limit on intake) during the year for an adult worker or the committed effective dose equivalent is likely to exceed 0.05 rem (0.5 mSv) for the occupationally exposed minor or de-clared pregnant woman.

In the revised 10 CFR Part 20, "Standards for Protection Against Radiation," 10 CFR 20.1201 es-tablishes radiation dose limits for occupationally ex-posed adults. These limits apply to the sum of the dose received from external exposure and the dose from internally deposited radioactive material. In 10 CFR 20.1201(a)(1), the annual limits for adults are (i) 5 reins (0.05 Sv) total effective dose equivalent or (ii) 50 reins (0.5 Sv) total organ dose equivalent to any single organ or tissue (other than the lens of the eye), whichever is more limiting. The occupational dose limits for minors in 10 CFR 20.1207 are 10% of the dose limit for adults, and 10 CFR 20.1208 estab-lishes a dose limit for the embryo/fetus of 0.5 rem (0.005 Sv) during the entire pregnancy.

The "total effective dose equivalent" is defined as the sum of the "deep-dose equivalent" (for exter-nal exposures) and the "committed effective dose equivalent" (for internal exposures). The total organ dose equivalent limit of 50 rems (0.5 Sv) specified in 10 CFR 20.1201(a) (1)(ii) applies to the sum of the "deep-dose equivalent" and the "committed dose equivalent" to any individual organ or tissue. The requirements in 10 CFR 20.1202 are for summing ex-ternal and internal doses to demonstrate compliance with the dose limits of 10 CFR 20.1201.

The Part 20 requirements for recording individ-ual monitoring results are contained in 10 CFR 20.2106. When monitoring is required under 10 CFR 20.1502, the monitoring results must be recorded on NRC Form 5 or equivalent.

Any information collection activities mentioned in this regulatory guide are contained as requirements in 10 CFR Part 20, which provides the regulatory basis for this guide. The information collection USNRC REGULATORY GUIDES Regulatory Guides are issued to describe and make available to the pub-lic methods acceptable to the NRC staff of implementing specific parts of the Commission's regulations, to delineate techniques used by the staff in evaluating specific problems or postulated accidents, or to pro-vide guidance to applicants. Regulatory Guides are not substitutes for regulations, and compliance with them is not required. Methods and solutions different from those set out in the guides will be acceptable if they provide a basis for the findings requisite to the issuance or continu-ance of a permit or license by the Commission.

This guide was issued after consideration of comments received from the public. Comments and suggestions for improvements in these guides are encouraged at all times, and guides will be revised, as ap-propriate, to accommodate comments and to reflect new information or experience.

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10.

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[

requirements in 10 CFR Part 20 have been cleared under OMB Clearance No. 3150-0014.

B. DISCUSSION This guide provides criteria acceptable to the NRC staff that may be used by licensees to determine when monitoring is required, and it describes meth-ods acceptable to the NRC staff for calculating occu-pational doses when the intake is known. Guidance on calculating doses to the embryo/fetus is contained in Regulatory Guide 8.36, "Radiation Dose to the Embryo/Fetus." Revision 1 to Regulatory Guide 8.9, "Interpretation of Bioassay Measurements," is under development and will provide guidance on determin-ing intakes from bioassay results. Guidance on deter-mining intakes from air sampling measurements is contained in Revision 1 to Regulatory Guide 8.25, "Air Sampling in the Workplace." Guidance on re-cording the calculated doses onto NRC Forms 4 and 5 is described in Revision 1 to Regulatory Guide 8.7, "Instructions for Recording and Reporting Occupa-tional Radiation Exposure Data."

The appendix to this guide gives examples of the calculations of internal and external doses for entry onto NRC Form 5.

C. REGULATORY POSITIONS

1.

MONITORING CRITERIA The monitoring requirements in 10 CFR Part 20 are summarized in Table 1. For external dose moni-toring, 10 CFR 2 0.1502(a) requires the use of indi-vidual monitoring devices. Individual monitoring de-vices are not required for monitoring the intake of radioactive material.

The monitoring requirements apply separately to each external dose type (i.e., deep-dose equivalent, shallow-dose equivalent to the skin, eye dose equiva-lent, and shallow-dose equivalent to the extremities).

1.1 Evaluation of Likely Annual Occupational Dose Evaluation of the likelihood of doses exceeding 10% of the limit should be based on the potential oc-cupational dose to the individual for the year. Doses that may have been received or will be received dur-ing the year from employment by another licensee are not included in the determination of monitoring re-quirements. The requirements in 10 CFR 20.1502 re-fer to each licensee. Each licensee makes the deter-mination independently. It would not be appropriate to base the monitoring requirements at one licensee's facility on exposure conditions at a different licen-see's facility. Rather, the need for monitoring at a fa-cility should be based on the exposure conditions at that facility only.

Evaluations of previous dosimetric or bioassay data may be considered in projecting doses. The use of and credit for respiratory protective equipment may be considered in the evaluations, provided use of the equipment is in compliance with the requirements of 10 CFR 20.1703. Surveys of dose rates and esti-mates of occupancy times may be used to estimate expected external doses. Measurements and predic-tions of airborne radionuclide concentrations and the expected duration of exposure may be used to predict radionuclide intakes. The potential for unlikely expo-sures and accident conditions need not be considered because these events, by definition, are not likely.

1.2 Establishing Categories of Workers for Monitoring If groups or categories of workers are exposed to similar radiological conditions, a single evaluation may be used to determine the need for monitoring.

For simplicity, licensees may establish routine opera-tional guidelines for categories of workers who will be monitored. For example, licensees may establish cri-teria or procedures for monitoring based on antici-pated area access or work functions.

1.3 Change in Exposure Conditions If an individual's radiation exposure conditions change during the year, the need to provide individ-ual monitoring should be reevaluated.

For example, consider an unmonitored individual whose work assignment is changed from periodic de-livery of supplies to a restricted area to performing maintenance activities within a radiation area. Under this new job assignment, if the licensee determines that the worker's dose is likely to exceed 10% of the limit, 10 CFR 20.1502 requires that monitoring be provided. When monitoring is required, 10 CFR 20.2106 requires that the monitored doses be re-corded.

Similarly, if reevaluation of a monitored individu-al's anticipated annual occupational dose indicates that the dose is likely to be below 10% of the limits, monitoring may be terminated. Even when the doses are actually below 10% of the limit, the doses meas-ured while monitoring was provided must be recorded pursuant to 10 CFR 20.2106 because the monitoring was provided to meet 10 CFR 20.1502.

1.4 Monitoring Performed But Not Required by 10 CFR 20.1502 Individual monitoring may be conducted for rea-sons other than those noted in 10 CFR 20.1502.

While the results of required monitoring are subject to the dose recording requirements of 10 CFR 20.2106, the results of monitoring provided when not 8.34-2

Table 1 Summary of 10 CFR Part 20 Monitoring Requirements The use of individual monitoring devices for external dose is required:

For adults who are likely to receive an annual dose in excess of any of the following (each evaluated sepa-rately):

0.5 rem (0.005 Sv) deep-dose equivalent.

1.5 rems (0.015 Sv) eye dose equivalent.

5 rems (0.05 Sv) shallow-dose equivalent to the skin.

5 rems (0.05 Sv) shallow-dose equivalent to any extremity.

For minors who are likely to receive an annual dose in excess of any of the following (each evaluated separately):

0.05 rem (0.5 mSv) deep-dose equivalent.

0.15 rem (1.5 mSv) eye dose equivalent.

0.5 rem (0.005 Sv) shallow-dose equivalent to the skin.

0.5 rem (0.005 Sv) shallow-dose equivalent to any extremity.

For declared pregnant women who are likely to receive an annual dose from occupational exposure in excess of 0.05 rem (0.5 mSv) deep-dose equivalent, although the dose limit applies to the entire gestation period.

Individuals entering a high or a very high radiation area.

Internal exposure monitoring (not necessarily individual monitoring devices) is required:

For adults likely to receive in 1 year an intake in excess of 10% of the applicable ALIs for ingestion and inhalation.

For minors and declared pregnant women likely to receive in 1 year a committed effective dose equivalent in excess of 0.05 rem (0.5 mSv).

required by 10 CFR 20.1502 are not subject to those dose recording requirements.

Surveys and monitoring results that serve as con-firmatory measures are not subject to the individual dose recordkeeping requirements of 10 CFR 20.2106(a) provided such results confirm that actual individual doses are less than 10% of the limits. These surveys and monitoring results may be used to meet 10 CFR 20.1501 requirements. An example of con-firmatory monitoring is an individual's annual bio-assay measurement used as confirmation of the ade-quacy of airborne control measures.

Another example is placing monitoring devices, such as ther-moluminescence dosimeters (TLDs), on a sample of workers to provide a confirmation that doses are not above those anticipated.

1.5 Detection Sensitivity The monitoring criteria contained in 10 CFR 20.1502 do not establish required levels of detection sensitivity, e.g., the lower limit of detection (LLD).

For example, it may not be feasible to actually con-firm intakes of 10% of the ALI, particularly for bioas-say measurements of some alpha-emitting radionu-clides. Therefore, monitoring thresholds should not be considered requirements on the sensitivity of a particular measurement. Workplace monitoring and occupancy factors should be considered, as appropri-ate, in evaluating potential exposures and monitoring requirements.

2.

DETERMINATION OF EXTERNAL DOSES There are three dose limits included in 10 CFR 20.1201 that apply to external exposure: deep dose to the whole body (5 rems or 0.05 Sv), shallow dose to the skin or extremities (50 rems or 0.5 Sv), and dose to the lens of the eye (15 rems or 0.15 Sv).

According to the definitions in 10 CFR 20.1003, the deep-dose equivalent to the whole body is considered to be at a tissue depth of 1 cm (1000 mg/cm2),

shallow-dose equivalent to the skin or extremities at 0.007 cm (7 mg/cm2), and eye dose equivalent at 0.3 cm (300 mg/cm2). In evaluating the eye dose equiva-lent, it is acceptable to take credit for the shielding provided by protective lenses.

8.34-3

2.1 Placement of Individual Monitoring Devices External dose is typically determined by the use of individual monitoring devices, such as film badges and thermoluminescence dosimeters (TLDs). The device for monitoring the whole body dose should be placed near the location expected to receive the high-est dose during the year (10 CFR 20.1201(c)). When the whole body is exposed fairly uniformly, the indi-vidual monitoring device is typically worn on the front of the upper torso.

If the radiation dose is highly nonuniform, caus-ing a specific part of the whole body (head, trunk, arms above the elbow, or legs above the knees) to receive a substantially higher dose than the rest of the whole body, the individual monitoring device should be placed near that part of the whole body expected to receive the highest dose. For example, if the dose rate to the head of an individual is expected to be higher than the dose rate to the trunk of the body, a monitoring device should be located on or close to the head so as to measure the dose received by the head.

If postexposure evaluations indicate that the maximum dose to a part of the whole body was sub-stantially higher than the dose measured by the indi-vidual monitoring device, an evaluation should be conducted to estimate the actual maximum dose.

2.2 Use of More Than One Dosimeter An acceptable alternative approach for highly nonuniform radiation fields is to use more than one dosimeter to separately track doses to different parts of the whole body. At the end of the year, each of the doses for each location would be summed. The deep-dose equivalent to be recorded would be that of the dosimeter location receiving the highest dose.

2.3 Extremity Monitoring If the licensee determines that extremity monitor-ing is required, it may be appropriate to use an ex-tremity dosimeter for some, but not all, radiation ex-posure. The licensee could supply an extremity dosimeter when exposure is nonuniform. When expo-sure is uniform, the shallow-dose equivalent meas-ured by a torso dosimeter would be representative of the shallow-dose equivalent to the extremities, and separate extremity monitoring would not be needed.

If protective gloves are used, it is acceptable to place the extremity dosimeter under the gloves.

tive dose equivalent is the 50-year effective dose equivalent that results when radioactive material is taken into the body, whether through inhalation, in-gestion, absorption through the skin, accidental injec-tion, or introduction through a wound. The contribu-tions from all occupational intakes for these modes of intake are added over the yearly time period for which the total committed effective dose equivalent is being evaluated. The regulatory requirements for de-termining the internal dose are in 10 CFR 20.1204.

Some noble gases in Appendix B to §§ 20.1001-20.2401 do not have inhalation ALI values listed and are listed "submersion" class. For these radio-nuclides, the internal dose is negligible compared to the external dose. These radionuclides may be ex-cluded from the determination of the internal dose.

There are at least five methods acceptable to the NRC staff for calculating committed effective dose equivalent from inhaled radioactive materials. The five methods are described below.

3.1 Use of Federal Guidance Report No. 11 Federal Guidance Report No. 11 (Ref. 1) lists the committed effective dose equivalent per unit in-take by inhalation in sieverts per becquerel in its Ta-ble 2.1. These values may be used directly after con-verting the units from sieverts per becquerel to rem per microcurie (Sv/Bq x 3.7 x 106 = rem/gCi).

3.2 Use of Stochastic Inhalation ALIs from 10 CFR Part 20 ALI values have been established for individual radionuclides and are presented in Table 1 in Appen-dix B to §§ 20.1001-20.2401. The ALI values for inhalation, presented in Column 2 in Table 1, corre-spond to a committed effective dose equivalent of 5 rems (0.05 Sv) or a committed dose equivalent of 50 rems (0.5 Sv) to any individual organ or tissue, whichever is more limiting. If the ALI value pre-sented in Table 1 is limited by the 50-rem committed dose equivalent, the controlling organ is listed directly below the ALI value, and the stochastic ALI value based on the 5-rem committed effective dose equiva-lent is listed in parentheses directly below the organ name. If a stochastic ALI is listed in parentheses, that value should be used to calculate the committed ef-fective dose equivalent. The committed effective dose equivalent for each radionuclide may be calculated, using the estimated radionuclide intake, by Equation 1.

3.

CALCULATION OF COMMITTED EFFEC-TIVE DOSE EQUIVALENT FROM INHALA-TION The internal dose component needed for evaluat-ing the total effective dose equivalent is the commit-ted effective dose equivalent. The committed effec-HjE =

5 Ii ALIjE Equation 1 where HiE

=

Committed effective dose equivalent from radionuclide i (rems) 8.34-4

Intake of radionuclide i by inhala-tion during the calendar year (gCi)

(If multiple intakes occurred during the year, I is the sum of all in-takes.)

ALIIE Value of the stochastic inhalation ALI (based on the committed effec-tive dose equivalent) from Column 2 of Table 1 in Appendix B to

§§ 20.1001-20.2401 (1tCi) 5

=

Committed effective dose equivalent from intake of 1 ALI (rems)

Hi E5 Cit 2000 DACs,,,0 where Equation 3 Hi.E

=

Committed effective dose equivalent from radionuclide i (rems)

C,

=

The airborne concentration of radionuclide i to which the worker is exposed (microcuries/ml) t

=

The duration of the exposure (hours) 2000 If intakes of more than one radionuclide oc-curred, the total committed effective dose equivalent will be the sum of the committed effective dose equivalents for all radionuclides.

The ALIs in Part 20 are based on a particle dis-tribution with a 1-micron activity median aerody-namic diameter. Those ALIs may be used regardless of the actual median diameter. However, the NRC allows adjustment of ALIs to account for particle size, but only with prior approval from the NRC (10 CFR 20.1204(c)).

3.3 Use of DACs from 10 CFR Part 20 Committed effective dose equivalent may also be calculated from exposures expressed in terms of DAC-hours.

If the DAC in Appendix B

to

§§ 20.1001-20.2401 for a radionuclide represents a stochastic value (i.e., the corresponding ALI does not have the name of an organ below it), the DAC may be used directly. If Appendix B to §§ 20.1001-20.2401 does not list a stochastic DAC, which will be the case any time there is a stochastic ALI value in parentheses, it is preferred (but not required) that the licensee calculate and use a stochastic DAC. The sto-chastic DAC can be calculated from the stochastic ALI (the ALI in parentheses) by the following equa-tion:

5

=

The number of hours in a workyear

=

Committed effective dose equivalent from annual intake of 1 ALI or 2000 DAC-hours (rems)

If there is a mixture of several radionuclides, it is permissible to disregard certain radionuclides in the mixture that are present in relatively small quantities (10 CFR 20.1204(g)). These radionuclides may be disregarded if the following conditions are met:

(1) the concentration of any radionuclide disregarded is less than 10% of its DAC; (2) the sum of these per-centages for all of the radionuclides disregarded in the mixture does not exceed 30%; and (3) the licen-see uses the total activity of the mixture in demon-strating compliance with the dose limits and monitor-ing requirements.

3.4 Use of ICRP Publication 30 The supplements to ICRP Publication 30 (Ref. 2) list "weighted committed dose equivalent to target or-gans or tissues per intake of unit activity" for inhala-tion in sieverts per becquerel. The sum of the values given is the committed effective dose equivalent.

ICRP Publication 30 (Ref. 2) does not give the sum, but the licensee can easily add the values given to calculate the sum. Then it is only necessary to convert from sieverts per becquerel to rems per microcurie (3.7 x 106 x Sv/Bq = rem/jLCi).

DACsto ALI1,.,

Equation 2 3.5 Use of Individual or Material-Specific 2.4 x 109 q

Information NRC regulations (10 CFR 20.1204(c)) state that where "When specific information on the physical and biochemical properties of the radionuclides taken into DACsocj

~=

The stochastic DAC for radio-the body or the behavior of the material in an indi-nuclide i (microcuries/ml) vidual is known, the licensee may... use that informa-tion to calculate the committed effective dose

ALIsoc,

= The stochastic ALI for radio-equivalent...... No prior NRC approval is required for nuclide i (microcuries) using this approach, but records must be kept.

2.4 x 109 = The volume of air inhaled by a worker in a workyear (ml).

Then This approach requires the licensee to do consid-erably more work and to have greater technical ex-pertise than the other approaches. Thus, the ap-proach is unlikely to be attractive to most licensees 8.34-5

L for small routine intakes. On the other hand, it might be attractive in the case of accidental large exposures if more accurate information would lead to a better estimate of the actual dose.

I.

= Intake of radionuclide i by inges-tion during the calendar year (lci)

When this approach is used, the dose to organs not "significantly irradiated" may be excluded from the calculation (10 CFR 20.1202(b)(3)).

4.

CALCULATION OF COMMITTED EFFEC-TIVE DOSE EQUIVALENT DUE TO INGESTION There are annual limits on intake (ALIs) for oc-cupational ingestion of radioactive material. Only one ingestion ALI is given for each radionuclide, whereas for inhalation a different ALI was given for each solu-bility class. Solubility classes are not used for inges-tion. The ingestion ALI given for each radionuclide is used for all chemical forms of that radionuclide.

If ingestion has occurred, the methods for deter-mining the committed effective dose equivalent are similar to the methods used for estimating inhalation dose. Four acceptable methods are described here.

Some noble gas radionuclides in Appendix B to

§§ 20.1001-20.2401 do not have ingestion ALI val-ues listed because the ingestion pathway does not contribute significantly to the dose. These radio-nuclides may be excluded from the determination of the internal dose from ingestion.

4.1 Use of Federal Guidance Report No. 11 Federal Guidance Report No. 11 (Ref. 1) lists in its Table 2.2 the committed effective dose equivalent per unit of intake by ingestion in sieverts per bec-querel. These values may be used directly after con-verting the units from sieverts per becquerel to rems per microcurie (by multiplying the Sv/Bq value by 3.7 x 106).

4.2 Use of Stochastic Ingestion ALIs from 10 CFR Part 20 If the amount of ingested radioactive material is known, the stochastic ingestion ALIs from Column 1 of Table 1 in Appendix B to §§ 20.1001-20.2401 may be used. Equation 4 may be used for this deter-mination.

HjE =

I Equation 4 ALi,E,oraI where ALIiE,ora1 = Value of the stochastic ingestion ALI for the committed effective dose equivalent from Column 1 of Table 1 in Appendix B to

§§ 20.1001-20.2401 (gtCi) 5

= Committed effective dose equiva-lent from annual intake of 1 ALI (reins) 4.3 Use of ICRP Publication 30 The supplements to ICRP Publication 30 (Ref. 2) list "weighted committed dose equivalent to target or-gans or tissues per intake of unit activity" for oral in-take in sieverts per becquerel. The sum of the values given is the committed effective dose equivalent.

ICRP Publication 30 does not give the sum, but the licensee can easily add the values given to calculate the sum. Then it is only necessary to convert from sieverts per becquerel to rems per microcurie (by multiplying the Sv/Bq value by 3.7 x 106).

4.4 Use of Individual or Material-Specific Information NRC regulations (10 CFR 20.1204(c)) allow the committed effective dose equivalent to be calculated based on specific information on the physical and biochemical properties of radionuclides taken into the body of a specific worker. The doses due to ingestion can be calculated using the specific information previ-ously described for inhalation.

5.

DETERMINATION OF ORGAN-SPECIFIC COMMITTED DOSE EQUIVALENTS The internal dose component needed for demon-strating compliance with the dose limit specified in 10 CFR 20.1201(a) (1)(ii) is the organ-specific commit-ted dose equivalent. The organ-specific committed dose equivalent is calculated for an individual organ.

Tissue weighting factors are not used.

Organ-specific committed dose equivalents need be calculated only if the committed effective dose equivalent exceeds 1 rem or if an overexposure has occurred, because if the committed effective dose equivalent is less than 1 rem and no overexposure has occurred, the 50-rem nonstochastic organ limit can-not be exceeded.

Five acceptable methods to calculate the organ-specific committed dose equivalent are described here.

5.1 Use of Federal Guidance Report No. 11 One method for calculating the organ-specific committed dose equivalent is to use the factors in Hj,E

= Committed effective dose equiva-lent from radionuclide i (rems) 8.34-6

Federal Guidance Report No.

11 (Ref.

1). The organ-specific exposure-to-dose conversion factors presented in Table 2.1 (for inhalation) and Table 2.2 (for ingestion) of Federal Guidance Report No. 11 (Ref. 1) provide acceptable data for calculating indi-vidual organ doses based on intakes as follows:

5.3 Use of DACs from Part 20 If a radionuclide has an ALI based on a non-stochastic dose limit to an organ, the corresponding DAC may be used to calculate the organ-specific committed dose equivalent to the organ with the high-est dose using the following equation:

HiT =

i; x DCFi x 3.7 x 106 Equation 5 50 Cit iT 2000 DAC, Equation 7 where HiT

= Committed dose equivalent to the tissue or organ from radionuclide i (reins)

HiT Ci

=

Committed dose equivalent to tissue or organ T from radionuclide i (rems)

=

The concentration of the radio-nuclide i (microcuries/ml)

Ii

= Intake of radionuclide i (gtCi)

DCFj

= Dose conversion factor for radio-nuclide i from Table 2.1 or 2.2 in Federal Guidance Report No. 11 (Sv/Bq) 3.7 x 106 = Conversion factor to convert from Sv/Bq to rem/p.Ci 5.2 Use of Nonstochastic Inhalation ALIs from Part 20 It is possible to calculate organ-specific commit-ted dose equivalents for those radioactive materials for which nonstochastic ALIs are given in 10 CFR Part 20. (Nonstochastic ALIs are those in which the organ is identified underneath the ALI in Appendix B to §§ 20.1001-20.2401.) The equation is:

Hi A

=

50 Ii Equation 6 ALIiT DACj

=

The nonstochastic DAC for radio-nuclide i (microcuries/ml) t

=

The duration of the exposure (hours) 2000

=

The number of hours in the workyear 50

=

Committed dose equivalent to maximum-exposed organ from an-nual intake of 1 ALI or 2000 DAC-hours (rems) where HiT

=

Committed dose equivalent to tissue or organ T from radionuclide i (rems)

I

=

Intake of radionuclide i by inhala-tion during the calendar year (RCi)

ALIT =

Value of the nonstochastic inhala-tion ALI for radionuclide i (based on the organ-specific committed dose equivalent) from Column 2 of Table 1 in Appendix B to

§§ 20.1001-20.2401 (gCi) 50

=

Committed dose equivalent to maxi-mum-exposed organ from inhalation of 2000 DAC-hours (rems)

If intakes during the monitoring period are from more than one radionuclide and the organs receiving the highest dose are different from each radionuclide, this method may substantially overestimate the maxi-mum organ dose. In this situation, the licensee may wish to use one of the other methods.

5.4 Use of ICRP Publication 30 The supplements to ICRP Publication 30 (Ref. 2) list "committed dose equivalent in target organs or tissues per intake of unit activity," in sieverts per bec-querel, to significantly exposed organs. These values may be used to calculate organ-specific committed dose equivalents after converting the units from Sv/

Bq to rem/~Ci.

5.5 Use of Individual or Material-Specific Information NRC regulations (10 CFR 20.1204(c)) state that the committed effective dose equivalent may be cal-culated based on specific information on the physical and biochemical properties of radionuclides taken into the body. Although not explicitly stated, the organ-specific committed dose equivalent may also be calculated based on specific information.

In general, if specific information is used to cal-culate the committed effective dose equivalent, it should also be used to calculate the organ-specific dose equivalent so that both dose calculations have the same basis.

8.34-7

L

6.

DOSES FROM INTAKES THROUGH WOUNDS OR ABSORPTION THROUGH SKIN According to 10 CFR 20.1202(d), the licensee must evaluate and, to the extent practical, account for intakes through wounds or skin absorption. (Dose from tritium absorption through the skin is taken into account in the DAC value in Appendix B to

§§ 20.1001-20.2401.) As a practical matter, the in-take by skin absorption of airborne radioactive mate-rials usually does not need to be considered because it will be negligible compared to the intake from inha-lation. It may be necessary to consider absorption through the skin when solutions containing dissolved radioactive material come in contact with the skin.

7.

RECORDING OF INDIVIDUAL MONITOR-ING RESULTS The requirements for recording individual moni-toring results are contained in 10 CFR 20.2106, which requires that the recording be done on NRC Form 5 or equivalent. NRC Form 5 is used to record, on an annual basis, doses received. Thus, for workers who work for the same licensee for the entire year, the monitoring period will normally be January 1 to December 31. The monitoring year may be adjusted as necessary to permit a smooth transition from one monitoring year to another-so long as the year begins and ends within the month of January, the change is made at the beginning of the year, and no day, is omitted or duplicated in consecutive years. A copy of NRC Form 5 and instructions for filling it out are con-tained in Revision 1 to Regulatory Guide 8.7, "In-structions for Recording and Reporting Occupational Exposure Data."

7.1 Summation of External and Internal Doses Summation of external and internal doses is re-quired in 10 CFR 20.1202 when both external moni-toring and internal monitoring of an individual are re-quired to meet 10 CFR 20.1502(a) and (b). The requirement for summation applies to the occupation-ally exposed adult and minor and to the embryo/fetus of a declared pregnant woman.

The requirements for summation of external and internal doses specified in 10 CFR 20.1202(a) are not applicable to the shallow-dose equivalent to the skin or extremities or to the eye dose equivalent. Only ex-ternal dose is considered in evaluating the shallow-dose equivalent to the skin and the extremities and the eye dose equivalent.

Total effective dose equivalent is calculated by summing the external component (deep-dose equiva-lent) and the internal component (committed effec-tive dose equivalent). Likewise, the total organ dose equivalent is calculated by summing the external com-ponent (deep-dose equivalent) and the internal com-ponent to the organ or tissue (committed dose equivalent to any organ or tissue).

7.2 Preferred Units The preferred unit for dose is the "rem."

The use of "millirems" on NRC Form 5 is permitted but is discouraged. The preferred unit for intakes is the "microcurie." NRC regulations (10 CFR 2 0.2101(a))

do not permit the use of the units "sieverts" or "bec-querels" on Part 20 records.

7.3 Roundoff of Doses Licensees should avoid entering doses on NRC Form 5 with more significant figures than justified by the precision of the basic measured values. In gen-eral, it is appropriate to enter dose values with two significant figures on NRC Form 5 using the standard rules for roundoff. Thus, a computer-generated cal-culated dose of "1.726931 rems" should be entered on NRC Form 5 as "1.7 rems." However, licensees should generally carry at least three significant figures in calculations to avoid loss of accuracy due to multi-ple roundoffs.

In addition, licensees should not enter doses smaller than 0.001 rem on NRC Form 5 because smaller values are insignificant relative to the dose limits. Therefore, a calculated committed effective dose equivalent of "0.006192 rem" should be en-tered as "0.006 rem," and a value of "0.000291 rem" should be entered as "0 rem."

The rounding recommended in this section is il-lustrated in the appendix to this guide.

D. IMPLEMENTATION The purpose of this section is to provide informa-tion to applicants and licensees regarding the NRC staff's plans for using this regulatory guide.

Except in those cases in which an applicant pro-poses an acceptable alternative method for complying with specified portions of the Commission's regula-tions, the methods described in this guide will be used in the evaluation of applications for new licenses, li-cense renewals, and license amendments and for evaluating compliance with 10 CFR 20.1001-20.2401.

8.34-8

REFERENCES

1.

K. F. Eckerman, A. B. Wolbarst, and A. C. B.

Richardson, "Limiting Values of Radionuclide Intake and Air Concentration and Dose Conver-sion Factors for Inhalation, Submersion, and In-gestion,"

Environmental Protection

Agency, Federal Guidance Report No. 11 (EPA 520/1-8-020), September 1988. This report may be purchased from the National Technical Informa-tion Service, Springfield, VA 22161. For infor-mation and credit card sales, call (703) 487-4 650.

2.

International Commission on Radiological Pro-tection, "Limits for Intakes of Radionuclides by Workers," ICRP Publication 30 (7-volume set, including supplements), Pergamon Press Inc.,

1982.

S.34-9

APPENDIX EXAMPLE OF THE CALCULATION OF OCCUPATIONAL DOSES This example illustrates the calculation 'of dose information needed for NRC Form 5, "Occupational Exposure Record for a Monitoring Period." An NRC Form 5 with the data and calculations in this example is provided to illustrate how to fill out the form. In this example, it is assumed that the individual was ex-posed to external radiation and received an intake by inhalation of five airborne radionuclides.

Deep-Dose Equivalent (Whole Body)

The licensee provided individual monitoring for the deep-dose equivalent (1-cm depth) based on the likelihood of exceeding 0.5 rem deep-dose equiva-lent. In this example, the sum of the dosimeter read-ing for the year is assumed to be 1.435 rems of low-LET radiation (gamma), which in the licensee's cal-culations is rounded to 1.44 rems, maintaining three significant figures for calculational purposes, but en-tered as 1.4 rems on NRC Form 5.

Eye Dose Equivalent The licensee provided monitoring for eye dose equivalent because the dose to the eye was likely to exceed 1.5 rems. The total annual dose measured at a depth of 0.3 cm by a dosimeter worn on the trunk was 1.720 rems. The rounded value of 1.7 is entered on NRC Form 5.

Shallow-Dose Equivalent The shallow-dose equivalent to the skin or ex-tremities must be monitored if the shallow-dose equivalent is likely to exceed 5 rems in the year. In this example, the licensee concluded at the start of the year that the shallow-dose equivalent was not likely to exceed 5 rems, and, therefore, monitoring of the shallow-dose equivalent was not required by 10 CFR 20.1502. Nevertheless, the licensee provided shallow-dose equivalent monitoring because the do-simeter supplier automatically provided a shallow-dose equivalent reading on all badges. The annual monitored total of the shallow-dose equivalent was l.85 rems, confirming that monitoring of the shallow-dose equivalent was not necessary. The licensee could enter "NR," meaning not required, on NRC Form 5 because monitoring the shallow-dose equivalent was not required by 10 CFR 20.1502. However, in this case the licensee decided, for the sake of complete-ness, to enter the rounded value of 1.9 rems as the shallow-dose equivalent, whole body column, but he entered "NR" under shallow-dose equivalent to the extremities because no extremity monitoring was re-quired or provided. The licensee also could have en-tered 1.9 rems on the basis that the extremities re-ceived about the same dose as the dosimeters located on the trunk. Either of those entries is acceptable. A value of zero should not be entered if no monitoring was provided. Any numerical value, including zero, should signify a measured or estimated dose.

Radionuclide Intakes The intake of each radionuclide must be entered separately. The solubility class of each radionuclide must be specified. The intake mode, inhalation (H) in this case, must also be entered. Based on air sam-pling data, worker stay times, and respirator protec-tion factors when applicable, the licensee calculated the intakes from inhalation (H), which are shown in Table A. 1 using this equation:

I=

Ci B t Equation A.1 APF where Ii

=

intake from radionuclide i in micro-curies C1

=

the concentration of radionuclide i in microcuries/ml B

=

the worker's breathing rate of 20,000 ml/min t

=

duration of the worker's exposure in minutes APF

=

assigned respiratory protection fac-tor, dimensionless All the data in Table A.1 must be entered on NRC Form 5.

Committed Effective Dose Equivalent The committed effective dose equivalent from each radionuclide is calculated by using Equation 1.

The data used in Equation 1 are shown in Table A.2.

The sum (1.3 rems) in Table A.2 must be en-tered on NRC Form 5.

Total Effective Dose Equivalent The total effective dose equivalent is the sum of the deep-dose equivalent and the sum of the commit-ted effective dose equivalent from all radionuclides.

In this case, the total effective dose equivalent is 1.44

+ 1.30 rems = 2.74 rems, which is rounded to 2.7 rems for entry onto NRC Form 5.

Organ-Specific Committed Dose Equivalent The organ-specific committed dose equivalents should be calculated because the committed effective 8.34-10

Table A.1 Worker Intakes Solubility Intake Intake Radionuclide Class Mode (microcuries)

U-238 D

H 0.022 U-235 D

H 0.0031 E-234 D

H 0.060 Cs-137 D

H 1.87 Ce-144 Y

H 2.07 Table A.2 Calculation of Committed Effective Dose Equivalent Radionuclide Intake, Ij ALIj,E CEDE and Class (microcuries)

(microcuries)

(rems)

U-238 (D) 0.022 2

0.055 U-235 (D) 0.0031 2

0.008 U-234 (D) 0.060 2

0.15 Cs-137 (D) 1.87 200 0.047 Ce-144 (Y) 2.07 10 1.04 Sum 1.30 dose equivalent exceeds 1 rem. The organ dose fac-tors in Federal Guidance Report No. 11* may be used. The organ dose factors from Table 2.1 of that report are reproduced in Table A.3. The dose factor for the "remainder" listed in Federal Guidance Re-port No. 11 is not listed here or used to calculate organ-specific committed dose equivalents because it does not represent a dose to a particular individual organ.

To calculate the organ-specific committed dose equivalent, multiply the intake by the organ dose fac-tor and a conversion factor to convert from Sv/Bq to rem/p.Ci. The equation is:

HjT Ii DCFTi 50-year committed dose to organ or tissue T from radionuclide i, in rems

= the intake of radionuclide i, in microcuries the dose conversion factor for or-gan or tissue T from radionuclide i, in Sv/Bq HT,;

= I, x DCFTJ x 3.7 x 106 Equation A.2 where The results are shown in Table A.4.

The doses in Table A.4 were calculated using the rounding method described in this guide.

Organ Dose The organ dose to the most exposed organ is the sum of the deep-dose equivalent and the committed dose equivalent to the organ with the largest dose. In this case, the deep-dose equivalent is 1.44 rems. The lung is the organ with the highest committed dose equivalent (6.22 rems). The organ dose is the sum.,

7.66 rems, which is rounded to 7.7 rems and entered on NRC Form 5.

• K.F. Eckerman, A.B. Wolbarst, and A.C.B. Richardson, "Limiting Values of Radionuclide Intake and Air Concentra-tion and Dose Conversion Factors for Inhalation, Submer-sion, and Ingeslion. " Environmental Protection Agency, Fed-eral Guidance Report No. 11 (EPA 520/1-88-020), Septem-ber 1988.

This report may be purchased from the National Technical Information Service, Springfield, VA 22161.

For information and credit card sales, call (703) 487-4650.

8.34-11

Table A.3 Organ Dose Factors From Federal Guidance Report No. 11 Dose Per Unit Intake (Sv/Bq)

Radionuclide Gonad Breast Lung R Marrow B Surface Thyroid U-238 (D) 2.23E-8 2.23E-8 2.80E-7 6.58E-7 9.78E-6 2.22E-8 U-235 (D) 2.37E-8 2.38E-8 2.95E-7 6.58E-7 1.01E-5 2.37E-8 U-234 (D) 2.50E-8 2.50E-8 3.18E-7 6.98E-7 1.09E-5 2.50E-8 Cs-137 (D) 8.76E-9 7.84E-9 8.82E-9 8.30E-9 7.94E-9 7.93E-9 Ce-144 (Y) 2.39E-10 3.48E-10 7.91E-7 2.88E-9 4.72E-9 2.92E-10 Table A.4 Calculated Organ-Specific Committed Dose Equivalents Organ-Specific Committed Dose Equivalent (rems)

Intake Radionuclide (pCi)

Gonad Breast Lung R Marrow B Surface Thyroid U-238(D) 0.022 0.002 0.002 0.023 0.054 0.796 0.002 U-235(D) 0.0031 0

0 0.003 0.008 0.116 0

U-234(D) 0.060 0.006 0.006 0.071 0.155 2.42 0.006 Cs-137(D) 1.87 0.061 0.054 0.061 0.057 0.055 0.055 Ce-144(Y) 2.07 0.002 0.003 6.06 0.022 0.036 0.002 Sum 0.071 0.065 6.22 0.296 3.42 0.065 8.34-12

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REGULATORY ANALYSIS A separate regulatory analysis was not prepared for this regulatory guide. The regulatory analysis pre-pared for 10 CFR Part 20, "Standards for Protection Against Radiation" (56 FR 23360), provides the regu-latorv basis for this guide and examines the costs and benefits of the rule as implemented by the guide. A copy of the "Regulatory Analysis for the Revision of 10 CFR Part 20" (PNL-6712, November 1988) is available for inspection and copying for a fee at the NRC Public Document Room, 2120 L Street NW.,

Washington, DC, as an enclosure to Part 20 (56 FR 23360).

8.34-14

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 FIRST CLASS MAIL POSTAGE AND FEES PAID USNRC PERMIT NO. G-67 OFFICIAL BUSINESS PENALTY FOR PRIVATE USE, $300