POLICY ISSUE

(Notation Vote)

December 4, 2002 SECY-02-0214

FOR: The Commissioners

FROM: William D. Travers

Executive Director for Operations /RA/

SUBJECT: GUIDANCE ON THE USE OF EFFECTIVE DOSE EQUIVALENT

IN EXTERNAL DOSE ASSESSMENTS

PURPOSE:

The Commission, in Staff Requirements Memorandum SRM-SECY-01-0127, directed the staff

to “...develop guidance that specifies when it is appropriate to use effective dose equivalent

rather than deep-dose equivalent for assessing the dose from external sources of radioactivity.” 

The purpose of this paper is to obtain the Commission’s approval to issue a proposed

Regulatory Issue Summary (RIS) on the appropriate use of effective dose equivalent for

assessing dose from external sources of radiation.

 

BACKGROUND:

The use of Deep Dose Equivalent (DDE), as specified in Part 20, has provided a satisfactory

method for licensees to show compliance with regulatory requirements in most ordinary

exposure situations involving personnel monitoring. However, difficulties sometimes arise

because the stochastic risk from radiation exposure is correlated with the effective dose

equivalent, but not with the DDE. The DDE will provide a reasonable indication of risk only

when its numerical value is close to that of the effective dose equivalent under the specified

exposure conditions. This is the case when the whole body is exposed in a uniform or nearly 

CONTACT: Sami Sherbini, NMSS/IMNS

301-415-7853
The Commissioners 2

uniform radiation field. It is not the case, however, when the radiation field is significantly nonuniform, or when parts of the body are shielded, or when the radiation is incident from an

unusual angle, such as from underfoot or overhead. In such situations, the numerical value of

the DDE is significantly different, and usually much higher, than that of the effective dose

equivalent under the given exposure conditions. 

An extreme example of the differences between the DDE and the effective dose equivalent is

the case of localized contamination on the skin, such as that from a hot particle, or exposure to

a narrow external radiation field. In such cases, the DDE at the exposure location may be very

high, but the corresponding effective dose equivalent, and hence the stochastic risk, is low. 

Another, less extreme, example is the exposure of medical personnel wearing protective aprons

during radiology procedures. Measuring DDE at the point of highest exposure may in this case

overestimate the effective dose equivalent, and hence the radiation risk, by up to an order of

magnitude or more outside the apron.

In an attempt to correct this situation, several methods have been developed that use the DDE

as measured by one or more dosimeters, together with a suitable formula, to obtain a dose

value that is numerically much closer to the effective dose equivalent. Underlying all of these

methods is the idea that, regardless of the method used to assess and assign doses, the

ultimate objective of any dose assessment situation is to obtain the most accurate estimate of

the effective dose equivalent without underestimating that value. This is a necessary condition

for any risk-based practice. 

The DDE was defined by the International Commission on Radiation Units and Measurements

(ICRU) to serve as an operational quantity and a surrogate to be used to provide a conservative

estimate, based on measurements, of the effective dose equivalent, which cannot be measured

directly. (Note: the ICRU calls the DDE the personal dose equivalent, but the definitions are

identical). Therefore, in situations that do not involve personnel monitoring, as for example

when the dose is calculated, the use of DDE to assess doses from external radiation fields is

not justified under any circumstances. In such cases the effective dose equivalent is calculated

directly. 

DISCUSSION

The attached RIS is written for the audience of radiation safety professionals, and thus uses the

terms and acronyms specific to complying with the requirements of 10 CFR Part 20. The

guidance encourages licensees to use the effective dose equivalent in all situations that do not

involve dose measurements using personnel dosimetry. Such situations include environmental

assessments, dose calculations for effluents, dose calculations in connection with proposed

licensing actions, calculations to show compliance with non-occupational dose limits and, in

general, any dose assessments based on calculations. Such calculations of the effective dose

equivalent are in fact now used in many regulated activities, both by the NRC and by licensees,

because the dose conversion factor tables that are used in these calculations, or that are

incorporated into the computer codes used to perform these calculations, are in fact effective

dose equivalent factors, and not DDE factors. 
The Commissioners 3

The RIS also specifies that licensees must still use the DDE, measured at the location of

highest exposure on the body, whenever the doses are being assessed on the basis of the

readings of personnel dosimetry. Exceptions would be considered and approved on a caseby-case basis. These exceptions include any method that is capable of providing more

accurate estimates of the effective dose equivalent. One such exception has already been

approved for use by medical personnel wearing protective aprons during radiology procedures. 

Another method was recently approved for use at the Entergy reactor sites.

RECOMMENDATION

The staff recommends that the proposed Regulatory Issue Summary (RIS) be issued to all

NRC licensees. 

/RA/

William D. Travers

Executive Director

 for Operations

Attachment:

Draft Regulatory Issues Summary 
The Commissioners 3

case basis. These exceptions include any method that is capable of providing more accurate

estimates of the effective dose equivalent. One such exception has already been approved

for use by medical personnel wearing protective aprons during radiology procedures. Another

method was recently approved for use at the Entergy reactor sites.

RECOMMENDATION

The staff recommends that the proposed Regulatory Issue Summary (RIS) be issued to all

NRC licensees. The staff also recommends that training on the issues involved in the RIS be

provided to selected Headquarters and Regional staff who may be required to answer

questions from licensees on this and related topics. 

/RA/

William D. Travers

Executive Director

 for Operations

Attachment:

Draft Regulatory Issues Summary 

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OFFICIAL RECORD COPY
UNITED STATES

NUCLEAR REGULATORY COMMISSION

October XX, 2002

Draft

NRC REGULATORY ISSUE SUMMARY 2002-XX

USE OF THE EFFECTIVE DOSE EQUIVALENT IN PLACE

OF THE DEEP DOSE EQUIVALENT IN DOSE ASSESSMENTS

ADDRESSEES

All U.S. Nuclear Regulatory Commission (NRC) licensees.

INTENT

The NRC is issuing this Regulatory Issue Summary (RIS) to provide guidance on situations in

which it is permissible to use the effective dose equivalent, in place of the deep dose

equivalent (DDE), in showing compliance with regulatory requirements.

BACKGROUND

The dose limits in 10 CFR Part 20 for occupationally exposed workers, as well as for members

of the public, are specified in terms of the quantity total effective dose equivalent (TEDE). 

Other Part 20 requirements, such as the criteria for license termination, are also specified in

terms of the TEDE, as are requirements specified in other parts of NRC’s regulations. 

The TEDE is defined in Part 20 as the sum of the DDE resulting from exposure to external

radiation, and the committed effective dose equivalent (CEDE) resulting from internal

contamination. However, Footnote 2, in the “Organ Dose weighting Factors” table in 10 CFR

20.1003, does permit approval of the use of organ and tissue weighting factors for external

exposures on a case-by-case basis, until specific guidance is issued. This RIS provides this

guidance. NRC, reading Part 20 as a whole, concludes that the footnote provides the staff

with the discretion to permit the use of effective dose equivalent for external exposures in

place of the DDE, in the definition of TEDE. In accordance with the discretion thus provided by

the footnote, TEDE may be redefined as the sum of the effective dose equivalent for external

exposure and the committed effective dose equivalent for internal exposure. When this

redefinition of TEDE is used, 10 CFR 20.1201(c) does not apply, because the DDE is no

longer used in the definition of TEDE.

ML #########

RIS 02-XX

Page 2 of 4
This RIS describes the exposure situations in which the use of the effective dose equivalent, in

place of the DDE, would be regarded by NRC as appropriate and acceptable. This RIS does

not affect the definition and use of the CEDE.

SUMMARY OF ISSUES

Use of Effective Dose equivalent

Licensees are encouraged to use the effective dose equivalent in place of the DDE in all

situations that do not involve direct monitoring of external exposures using personnel

dosimetry. Such situations include, but are not limited to: (1) calculating offsite doses resulting

from effluents; (2) calculating doses from contaminated soils and buildings; (3) assessing the

effects of ALARA (As Low As Reasonably Achievable) measures, such as installation of

shielding or system decontaminations; (4) assessing the environmental impacts of proposed

licensing actions; (5) calculations in connection with license termination and release of sites,

(6) assessing doses resulting from localized skin contaminations, and (7) all other situations in

which the doses are calculated rather than measured with personnel dosimetry. No prior NRC

approval is required when using the effective dose equivalent from external exposure in place

of the DDE, in such situations. The tissue weighting factors to be used in these effective dose

calculations must be those listed in 10 CFR 20.1003. Use of other weighting factors requires

case-by-case approval from the NRC.

There are several reasons for adopting this position: (1) the effective dose equivalent is the

primary radiation protection quantity, linked directly to the risks resulting from radiation

exposure, whereas the DDE is a surrogate operational quantity intended to be used in

monitoring situations as an approximation to the effective dose equivalent, which cannot be

measured directly; (2) when doses are to be calculated, or otherwise estimated, in ways that

do not involve personnel dosimetry, the effective dose equivalent is usually just as easily

calculated as is the DDE, and in many situations it may be easier to estimate; (3) many of the

tabulations of dose conversion factors currently used in dose assessments are in terms of the

effective dose equivalent, not DDE; (4) most software used in dose assessments refer to

tabulations of effective dose equivalent conversion factors, not DDE factors; (5) in situations

involving dose calculations, the effective dose equivalent is a well-defined dosimetric quantity,

whereas the DDE is not.

When recording or reporting doses in situations in which the effective dose equivalent from

external fields is assessed in place of the DDE, the value of the effective dose equivalent is

entered in place of the DDE in recording or reporting forms, such as NRC’s Forms 4 or 5.

Use of Deep Dose equivalent

The above guidance does not apply to situations in which individual doses from external

radiation fields are to be measured using personnel dosimetry. In such situations, because the

effective dose equivalent cannot be measured directly, NRC still requires the use of the DDE,

RIS 02-XX

Page 3 of 4
as defined in Part 20, as an estimator of the effective dose equivalent. It has been shown that,

for most practical situations involving personnel monitoring, the DDE provides a reasonable,

conservative, and often the best, estimate for the effective dose equivalent. It is also a

quantity that is well-suited to measurement using dosimeters.

Need for NRC Approval when Estimating Effective Dose Equivalent by Measurements

In personnel monitoring situations for which this use of the DDE measured at the location of

highest exposure may not be desirable, NRC will grant approval for other methods of dose

monitoring, on a case-by-case basis, if the proposed methods can be shown to be technically

adequate for the intended use.

One such situation is monitoring of personnel working under conditions where a substantial

part of the body is shielded as, for example, when wearing protective aprons in medical

radiology. Another involves radiation fields that are very non-uniform, or that irradiate only

small parts of the body, such as the upper extremities, but not the torso. Empirical and semiempirical methods are available, in such cases, that involve the use of one or more

dosimeters, together with an appropriate formula, to provide a better estimate of the effective

dose equivalent than is possible using the DDE as described above. However, because these

methods are often specific to certain limited exposure situations, and can be easily misapplied,

NRC requires that licensees obtain approval before using them. NRC will grant such

approvals on a case-by-case basis if the licensee is able to demonstrate that the proposed

method will provide reasonable dose estimates under the exposure conditions for which it will

be used. NRC may also provide generic approval for a specific method through issuance of a

generic communication or other means of providing guidance to licensees. One such general

approval has already been granted, and applies only to medical personnel wearing protective

aprons during radiology procedures (see RIS 2002-006). In addition, Entergy has recently

been granted approval to use an EPRI two-badge method for estimating effective dose

equivalent at their sites.

BACKFIT DISCUSSION

This RIS does not require any action or written response or require any modification to plant

structures, systems, components, or designs of facilities; therefore, the staff did not perform a

backfit analysis.

FEDERAL REGISTER NOTICE

A notice of opportunity for public comment was not published in the Federal register because

this RIS is information and pertains to a staff position that does not represent a departure from

current regulatory requirements and practices.

RIS 02-XX

Page 4 of 4
PAPERWORK REDUCTION ACT STATEMENT

This RIS does not request any information collection.

If you have any questions about this RIS, please contact the persons listed below or the

appropriate Office of Nuclear Reactor regulation project manager.

Donald A Cool, Director

Division of Industrial and

 Medical Nuclear Safety

Office of Nuclear Material Safety

 and Safeguards

William D. Beckner, Program Director

Operating Reactor Improvements Program

 Division of Regulatory Improvements Programs

Office of Nuclear reactor Regulation

Technical contact: Sami Sherbini, NMSS

301-415-7853

E-mail:sxs2@nrc.gov

Roger Pedersen, NRR

301-415-3162

E-mail:rlpd@nrc.gov

 OFC IMNS NMSS NRR IMNS NRR

 NAME SSherbini EKraus RPedersen DCool WBeckner

 DATE / /02 7/17/02 / /02 / /02 / /02