UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS

WASHINGTON, D.C. 20555-0001

August 22, 2003

NRC INFORMATION NOTICE 2003-12: PROBLEMS INVOLVED IN MONITORING DOSE

TO THE HANDS RESULTING FROM THE

HANDLING OF RADIOPHARMACEUTICALS

Addressees:

All holders of 10 CFR Parts 32, 33, and 35 licenses.

Purpose:

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to alert

licensees of potential difficulties that may be encountered when monitoring doses to the hands

of workers involved in handling radiopharmaceuticals. This IN describes some of these

difficulties, the work that is being conducted to resolve them, and interim guidance that NRC will

adopt pending completion of this work. It is expected that recipients will review the information

for applicability to their facilities and consider actions, as appropriate, to avoid similar problems. 

However, suggestions contained in the IN are not NRC requirements; therefore, no specific

action nor written response is required.

Background:

Handling of radiopharmaceuticals contained in syringes, vials, and other vessels exposes the

workers’ hands to radiation doses that may, in the course of a year, approach a significant

fraction of the regulatory limit on the shallow dose equivalent (SDE), which is the limit that

normally applies to such exposures. The practice has been, for many years, to monitor these

doses using ring dosimeters worn on one or more fingers of one or both hands, depending on

the details of the activity that produces the exposure. The highest ring dosimeter reading is

normally considered to provide a measure of the SDE received, and is used to show

compliance with the applicable dose limit.

During the past year or so, NRC inspectors have focused attention on this practice, and have

concluded that, at least in some cases, the dosimeters may be underestimating the doses they

are supposed to be measuring. This conclusion was reached because the dose that must be

assessed for the worker is the dose at the location of the highest exposure on the extremity. 

When handling radiopharmaceuticals, it may happen that the location of the highest exposure is

not the same as the location of the ring dosimeter, in which case the dosimeter will

underestimate that dose. This is particularly true when handling radioactive materials with the

fingertips, thus creating a sharp dose gradient between the location of highest exposure, which 

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is likely to be at the fingertip, and the location of the dosimeter, which is normally at the base of

the finger. Under these conditions, the dosimeter may not provide a sufficiently accurate

measure of the SDE for purposes of showing compliance, and a correction factor may be

warranted, in such cases, to adjust the dosimeter reading.

In response to these findings, some licensees have undertaken some measurements in an

attempt to estimate the value of such a correction factor. It is clear that this factor will vary

depending on the details of the handling activities, and this has been confirmed by the

measurements. The results obtained by the licensees, as well as those published in the

professional literature, showed factors ranging from very close to 1 up to 2, or in some cases,

higher values, with an average of roughly 1.2 - 1.4. These factors were estimated using the

ratio of the dose measured at the fingertip to that measured by the ring badge. Based on these

results and other considerations, some licensees have concluded that their activities are such

that their dose measurements do not require a correction factor or, in effect, that the

appropriate factor for them is 1.

This situation has been complicated by the change in the SDE limit, which became effective in

June 2002. The SDE limit has remained numerically the same, namely 0.5 Sv (50 rem) per

year to the extremities. However, whereas the old rule required that the dose be averaged over

an area of 1 cm2 of skin, the new rule requires that the dose be averaged over a skin area of 10

cm2

 (10 CFR 20.1201(c)). The effect of this change has been two-fold. For uniform, or nearly

uniform, exposures, over the extremity, the effect is negligible. However, for situations involving

high dose gradients, which is the case when handling radioactive materials with the fingertips,

the new rule results in an assessed dose that may be lower than would have been assessed

under the old rule, the extent of the reduction depending on the details of the exposure. This in

turn means that any correction factor that may have been applied to the ring badge reading

under the old rule is most likely to be closer to 1 under the revised rule. 

The second effect of the rule change is that it now defines the limit in terms of a quantity that is

not directly measurable, without specialized measurement techniques, under conditions of high

dose gradients. Under the old rule, measuring the dose at the point of highest exposure, such

as at the fingertips, by placing a dosimeter at that location, provided a fairly good approximation

of the dose averaged over an area of 1 cm2 , even in the presence of a high dose gradient. 

However, such a measurement does not provide a good estimate of the dose averaged over an

area of 10 cm2

. The required dose must now be measured using special measurement

techniques, or calculated. Such measurements or calculations enable estimation of any

correction factors that should be used with finger ring dosimeters, to permit reasonably

accurate estimation of the required SDE. It should be noted that this is not an unusual situation

in applied dosimetry, but only one that is made somewhat more than usually difficult because of

the relatively large area over which the dose must be averaged.

Discussion:

NRC and the radiopharmaceutical industry are currently conducting studies and measurements

designed to provide estimates of the appropriate correction factors that should be used with

ring dosimeters to enable accurate assessment of the SDE. It is expected, as a result of the

revised SDE limit, that these correction factors will be close to unity, but may be sufficiently

different to warrant their routine use in assessing the SDE. Until this work is completed, and

licensees are notified of its results and conclusions, NRC will accept the reading of the finger

ring dosimeter, without application of a geometry correction factor, as being sufficiently
IN 2003-12

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accurate to provide a direct indication of the SDE received by the worker provided the ring

dosimeter is worn on the finger that is expected to receive the highest dose. NRC will

reconsider this approach, and licensees will be notified of the new guidance, when the ongoing

work to resolve this matter is completed. In the interim, licensees are reminded of the

regulatory requirement to keep doses As Low As is Reasonably Achievable (ALARA) to ensure

that, even if the appropriate correction factor is found to be higher than 1, the worker will

nevertheless be adequately protected, and the SDE limit will not be exceeded.

This notice requires no specific action nor written response. If you have any questions about

the information in this notice, please contact one of the technical contacts listed below or the

appropriate regional office.

/RA/ Patricia K. Holahan, for

Charles L. Miller, Director

Division of Industrial and 

 Medical Nuclear Safety

Office of Nuclear Material Safety

 and Safeguards

Technical Contacts: Sami Sherbini, NMSS Anita Turner, Ph.D., NMSS

(301)415-7853 (301) 415-5508

Sxs2@nrc.gov Alt@nrc.gov

Joseph DeCicco, NMSS

(301) 415-7833

Jxd1@nrc.gov

Attachments:

1. List of recently issued NMSS Information Notices 

2. List of recently issued NRC Information Notices