[Federal Register Volume 67, Number 66 (Friday, April 5, 2002)]
[Rules and Regulations]
[Pages 16298-16304]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-8246]


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NUCLEAR REGULATORY COMMISSION

10 CFR Part 20

RIN 3150-AG25


Revision of the Skin Dose Limit

AGENCY: Nuclear Regulatory Commission.

ACTION: Final rule.

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SUMMARY: The Nuclear Regulatory Commission (NRC) is amending its 
regulations in 10 CFR part 20 to change the definition and method of 
calculating Shallow-dose equivalents (SDEs) by specifying that the 
assigned SDE must be the dose averaged over the 10 square centimeters 
of skin receiving the highest exposure, rather than 1 square centimeter 
as stated in the existing regulation. A result of this rulemaking is to 
make the skin dose limit less restrictive when small areas of skin are 
irradiated (i.e. more representative of actual health risks) and to 
address skin and extremity doses from all source geometries under a 
single limit. This change requires measuring or calculating SDEs from 
discrete radioactive particles (DRPs) on or off the skin, from very 
small areas (1.0 square centimeter) of skin contamination, and from any 
other source of SDE by averaging the measured or calculated dose over 
the most highly exposed, contiguous 10 square centimeters for 
comparison to the skin dose limit of 50 rem (0.5 Sv). The Commission 
believes that although the less restrictive limit on dose to small 
areas of the skin might permit more frequent, transient, observable 
effects such as reddening of the skin, the change nevertheless 
represents a substantial increase in worker protection because reduced 
monitoring for DRPs will result in reduced external dose and reduced 
use of protective clothing will result in fewer industrial hazards in 
the workplace.

EFFECTIVE DATE: June 4, 2002.

FOR FURTHER INFORMATION CONTACT: Alan K. Roecklein, Office of Nuclear 
Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, DC 
20555-0001, telephone (301) 415-3883; e-mail [email protected].

SUPPLEMENTARY INFORMATION:

I. Background

    With the installation of very sensitive portal monitors in the mid- 
and late-1980s, many nuclear power plants detected contamination of 
individuals and their clothing by small, usually microscopic, highly 
radioactive beta or beta-gamma emitting particles having relatively 
high specific activity. These particles, known as ``discrete 
radioactive particles'' (DRPs) and sometimes ``hot particles,'' most 
commonly contain \60\ Co or fission products. DRPs apparently become 
electrically charged as a result of radioactive decay and, therefore, 
tend to be fairly mobile. DRP movement in the workplace is 
unpredictable and, thus, worker contamination is difficult to control. 
A unique aspect of DRPs on or very near the skin is that very small 
amounts of tissue can be exposed to large, highly nonuniform doses. 
These intense, localized irradiations may produce deterministic 
effects, such as reddening of the skin, transient breaks in the skin or 
necrosis of small areas of the skin, but the stochastic risk of 
inducing skin cancer due to a DRP exposure is negligible.
    In the late-1990s, a materials licensee reported that workers 
received DRP exposures while manufacturing radiographic sources. In 
addition to the DRP concern, several events have occurred involving 
contamination of very small areas (1.0 square centimeter) of skin, 
primarily in the handling of solutions of highly concentrated 
radiopharmaceuticals. Although these contamination events produce 
relatively large doses to very small areas of skin, they are known to 
result in insignificant overall health detriments. Nevertheless, under 
existing provisions in NRC regulations, several of these contamination 
events were defined as overexposures, and resulted in enforcement 
actions, with the result that workers could not be assigned work in 
radiation areas for the balance of the year. These consequences were 
not commensurate with the actual health detriment.
    The principal stochastic risk associated with irradiation of the 
skin is non-melanoma skin cancer (that is, basal cell and squamous cell 
skin cancer). The risk of skin cancer following irradiation of the skin 
by DRPs, or from very small areas of contamination, is not comparable 
to irradiation of extended areas of the skin because of the very small 
number of cells involved and the greater potential for high local beta 
particle dose to kill cells rather than cause transformation to a 
precancerous stage. In Report No. 106, ``Limit for Exposure to ``Hot 
Particles'' on the Skin'' (1989), the Congressionally chartered 
National Council on Radiation Protection and Measurements (NCRP) 
conservatively estimated the risk of skin cancer following a DRP dose 
of 50 rem (0.5 Sv) to an area of 2 mm 2 to be 7  x  10 
-7 Gy -1 (7  x  10 -9 rad 
-1), and the risk of skin cancer mortality to be about 1 x 
10 -9 Gy -1 (1  x  10 -11 rad 
-1). Because the risk of stochastic effects (i.e., cancer) 
from gamma and beta radiation from DRPs has been shown to be negligible 
for DRP exposures to the skin, induction of skin cancer is of less 
concern than the potential for deterministic effects.
    In 1991, the NRC revised Title 10, part 20 of the Code of Federal 
Regulations and its occupational dose limit for the skin of the whole 
body to 50 rem (0.5 Sv) SDE per year to prevent deterministic effects 
that might result from a lifetime exposure at the dose limit (56 FR 
23360; May 21, 1991). This dose limit for the skin is specified in 10 
CFR 20.1201(a)(2)(ii), and is intended to prevent damage to areas of 
the skin that are large relative to areas exposed by DRPs on the skin, 
and that could compromise skin function or appearance. The NRC noted in 
that rulemaking that certain issues ``are being resolved in other 
rulemaking proceedings because of either their scope, complexity, or 
timing.'' One of the issues that was listed concerned limits and 
calculational procedures for dealing with the DRP issue. It was 
recognized that the current skin dose limit was overly conservative for 
DRP doses and SDEs to very small areas of the skin. The final rule 
stated that there would be a rulemaking to set limits for skin 
irradiation by DRPs. This amendment to 10 CFR part 20 responds, in 
part, to that commitment.
    The existing part 20 skin dose limit of 50 rem (0.5 Sv) averaged 
over 1 square centimeter was intended to apply to a relatively uniform 
dose to a larger area of skin than that usually exposed by DRPs with 
the objective of preventing deterministic damage to the skin. Because 
the NCRP considered this limit to be overly conservative for DRPs on or 
very near the skin, the NRC announced an interim enforcement discretion

[[Page 16299]]

policy in Information Notice (IN) 90-48, ``Enforcement Policy for Hot 
Particle Exposures'' (55 FR 31113; July 31, 1990). That policy 
addressed reporting and mitigation if a DRP dose exceeded the existing 
limit of 50 rem (0.5 Sv) over 1 square centimeter, and stated that the 
NRC would take enforcement action for overexposures if the DRP beta 
emission exceeded 75 Ci-hrs (approximately 300-500 rads). To 
avoid DRP doses greater than 50 rem (0.5 Sv) and the resulting 
reporting requirement, licensees monitor workers for DRP contamination 
frequently during the work shift. This results in additional external 
dose either to the workers, who incur additional exposure time in 
exiting and reentering the restricted area, or to the radiation 
protection staff, who must enter the restricted area to perform the 
monitoring.
    In 1988, the NRC contracted with Brookhaven National Laboratory 
(BNL) to study the health effects of DRPs on the skin and initiated a 
contract with the NCRP to develop guidance on controlling DRP doses. In 
NUREG/CR-6531, ``Effects of Radioactive Hot Particles on Pig Skin'' 
(June 1997), BNL provided data on the probability that irradiation of 
the skin by DRPs in contact with or near the skin would produce breaks 
in the skin and demonstrated that these effects would be very unlikely 
to pose any serious health problems to workers. The BNL work examined 
the nonuniform, highly concentrated dose to 1 square centimeter from 
DRPs in contact with or near the skin, and not the dose that would be 
delivered to the adjacent skin tissue. This BNL data was supported by 
other reported studies and similar experiments performed by the 
Electric Power Research Institute (EPRI) as reported in EPRI TR-104781, 
``Skin Injuries From Discrete Radioactive Particles'' (1994). 
Consequently, in Report No. 130, ``Biological Effects and Exposure 
Limits for ``Hot Particles'' (1999), the NCRP recommended a dose-
limiting guideline for DRPs of 50 rads (0.5 Gy) averaged over the most 
highly exposed 10 square centimeters.
    In October 1998, the NRC staff submitted a rulemaking plan (SECY-
98-245) entitled ``Protection Against Discrete Radioactive Particle 
(DRP) Exposures (10 CFR Part 20).'' In that plan the NRC staff proposed 
establishing a constraint of 300 rads (3 Gy) over 1 square centimeter 
as a program design guideline or action level, and a limit of 1000 rads 
(10 Gy) over 1 square centimeter for DRPs on or near the skin. The 
existing skin dose limit would have been retained for all other skin 
doses. The intent of that proposed amendment was to reduce the 
additional external dose incurred by workers in monitoring for DRP 
contamination during work shifts and to reduce unnecessary regulatory 
burden by adopting more realistic thresholds for DRP dose control and 
reporting requirements. In a staff requirements memorandum (SRM) dated 
December 23, 1998, the Commission directed the NRC staff to proceed 
with rulemaking as proposed, but to use 500 rads (5 Gy) per 1 square 
centimeter as the dose limit to be consistent with the recommendations 
in NCRP Report No. 106.
    In March 1999, several industry experts who had reviewed the 
publicly available rulemaking plan and SRM suggested that the planned 
action would not accomplish one of the intended objectives, that is, to 
reduce the frequency of worker monitoring. The industry concern argued 
against use of a DRP dose constraint with a 500-rem (5.0-Sv) limit, and 
supported use of the NCRP-recommended skin dose limit that is adopted 
in this rule. Specifically, the industry concern stated that, of all 
DRP events, fewer than 10 percent are on, or near enough to, the skin 
for the proposed constraint and limit to apply. Most DRP events (> 90 
percent) are on clothing or hair, or are far enough away from the skin 
(and most likely moving) so that the dose to the skin is more uniform 
and spread over a larger area. In that case, the existing 50-rem (0.5-
Sv) skin dose limit would be applicable. This information suggested 
that a reduction in DRP monitoring frequency, and the associated 
external dose, could not be realized for most DRP exposures, because of 
the need to prevent exceeding the existing skin dose limit. Because the 
licensee may not know in advance whether the DRP is on the skin or 
moving, the licensee would need to assume that the existing skin dose 
limit was applicable.
    The justification for proposing a constraint, or action level, of 
300 rads (3.0 Gy) over 1 square centimeter was in large part to reduce 
the additional external dose incurred by plant staff from frequent 
monitoring to avoid having to report a DRP dose that exceeded the 
existing 50-rem (0.5-Sv) skin dose limit. If more than 90 percent of 
DRPs are off the skin and irradiate a relatively large area, the 
existing skin dose limit would be controlling and the constraint would 
only rarely be used. The NRC staff concluded that little relief from 
monitoring dose would result from implementing the constraint and the 
500-rad (5-Gy) limit. In a memorandum to the Commission dated October 
27, 1999 (COMSECY-00-0009), the NRC staff explained why the constraint 
with a limit of 500 rads (5 Gy) would not accomplish this intended 
objective, and recommended further work to identify an effective 
regulatory approach. In an SRM dated March 16, 2000, the Commission 
directed the NRC staff to contract with the NCRP to provide additional 
technical support on this issue.
    In December 1999, the NCRP had published Report No. 130, 
``Biological Effects and Exposure Limits for `Hot Particles'.'' In that 
report the NCRP recommended that the dose to skin at a depth of 70 
m (7 mg/cm2) from hot particles on skin (including 
the ear), hair, or clothing be limited to no more than 50 rads (0.5 Gy) 
averaged over the most highly exposed 10 square centimeters of skin.
    The averaging area of 10 square centimeters, recommended by the 
NCRP, is applicable to both the case when a DRP is on the skin or a 
very small area of skin is contaminated, and the case when a DRP is on 
clothing and moving about exposing an area on the order of 10 square 
centimeters or more. In the former case, averaging the very localized 
dose over 10 square centimeters results in a dose value that more 
appropriately reflects the risk associated with exposure of a small 
area. In the latter case, averaging a relatively uniform dose to the 
entire 10 square centimeters results in a dose limit that is equivalent 
to the current 50 rem over 1 square centimeter. Thus, the limit 
decreases as the exposed skin area increases to 10 square centimeters, 
consistent with the expectation that the risk of an effect increases 
with increasing area of skin exposed to a given dose level. This 
averaging area is also consistent with the skin dose limiting system 
adopted by the Department of Energy in 10 CFR part 835.
    In an effort to find the least burdensome regulatory requirement 
for controlling DRP doses, as well as other skin doses, while 
maintaining an adequate level of worker protection, the NRC staff 
requested that the NCRP consider the advisability of applying its 
proposed limit for DRP exposures to all skin dose geometries. In March 
2001, the NCRP published Statement No. 9, ``Extension of the Skin 
Exposure Limit for Hot Particles to Other Sources of Skin 
Irradiation,'' which can be found on the NCRP Website at www.ncrp.com/statemnt.html. In this statement, the NCRP recommended that the 
absorbed radiation dose to skin at a depth of 70 m (7 mg/cm 
2) from any source of irradiation be limited to 50 rads (0.5 
Gy) averaged over the most highly exposed 10 square centimeters of 
skin.

[[Page 16300]]

    Dr. John Baum, Ph.D., an NRC consultant, reviewed the health 
effects implications of the NCRP recommendation. Dr. Baum wrote a 
technical paper entitled ``Analysis of Potential Radiobiological 
Effects Related to a Unified Skin Dose Limit,'' that was published in 
the June 2001 issue (pp. 537-543) of the peer-reviewed journal Health 
Physics. In this paper, Dr. Baum estimated the probabilities and 
severity of both stochastic and deterministic effects for a wide range 
of exposure scenarios based on the research done by BNL and other 
research facilities, as well as information found in NCRP Report Nos. 
106 and 130. Published data from experimental and epidemiological 
studies, as well as calculations of radial- and depth-dose 
distributions, show that skin exposures at the dose limit of 50 rem 
(0.5 Sv) SDE averaged over 10 cm2 could result in stochastic 
risks of 6.6  x  10-10 rem-1 and 3.2  x  
10-7 rem-1 for fatal and nonfatal skin cancers 
respectively, confirming that stochastic risks at the proposed limit 
are small.
    Given exposures at the proposed skin dose limit, that is, 50 rem 
(0.5 Sv) averaged over 10 square centimeters, Dr. Baum estimated that 
the worst-case deterministic effects are a 5-percent probability of 
erythema if all of the dose (500 rem) were delivered to an area of 2.5 
square centimeters, and a 50-percent probability that measurable dermal 
thinning would be observable if all of the dose were delivered to an 
area of 0.5 square centimeters. At this dose, no acute cell killing or 
skin ulceration was predicted for DRPs 3 or more millimeters off the 
skin because the dose is distributed over too large an area. The worst 
case probability of producing a barely detectable scab as a result of 
acute cell killing was estimated to be 10 percent for 60 Co 
or activated fuel DRPs located about 0.4 mm off the skin. Additional 
discussion of implications of the health effects associated with the 
proposed unified skin dose limit can be found in the regulatory 
analysis developed for this rulemaking.
    The NRC published a proposed rule in the Federal Register on July 
12, 2001 (66 FR 36502). That rule proposed changing the method of 
calculating SDEs to the skin or the extremities by specifying in 10 CFR 
20.1201(c) that the assigned SDE must be the dose averaged over the 
contiguous 10 square centimeters of skin receiving the highest 
exposure. Shortly after publishing the proposed rule, the NRC monitored 
a discussion of the rule that took place on a publicly accessible 
radiation protection bulletin board (RADSAFE). Comments were favorable 
regarding the intent and justification of the rule. However, radiation 
protection practitioners in the field raised several technical 
questions regarding implementation guidance. Although this exchange 
does not technically constitute public comment, the NRC staff has 
decided to note that parallel to this rulemaking, an effort is underway 
to contract for a major revision to the VARSKIN II computer code. This 
revision is expected to address calculations that will accommodate the 
new skin dose limit and address the technical questions raised in the 
RADSAFE discussion of the rule.

II. Analysis of Public Comments and Staff Response

    The NRC received nine letters of public comment, all supporting the 
proposed rule. Mallinckrodt, a subsidiary of Tyco Healthcare, commented 
that it is in favor of the proposed revision of the skin dose limit and 
agrees with the NCRP's recommendations because the new rule encompasses 
SDE from all sources into one limit. The Council on Radionuclides and 
Radiopharmaceuticals (CORAR), an association of NRC and Agreement State 
licensees that use unsealed sources of radioactive materials, fully 
supported the proposed rule. CORAR stated that the new limit would be 
more protective of workers, and more comparable to current annual 
limits for deep dose and lens of the eye dose than the current limit, 
would establish a skin dose limit on a risk-informed basis, and would 
simplify the regulations.
    CORAR requested clarification regarding the limit on deep-dose 
equivalent (DDE) to the extremities. No such limit exists. DDE, which 
Sec. 20.1201(a)(1) limits to 5 rem (50 mSv) in a year, is defined as 
applying to external whole-body exposure, and the whole body is defined 
as excluding the extremities. The SDE limit of 50 rems (0.50 Sv) 
averaged over 10 square centimeters is considered to adequately protect 
against any associated DDE to the less-radiosensitive deep tissues of 
the extremities.
    CORAR noted that the NRC should allow licensees to estimate doses 
for the actual skin thickness involved, rather than a tissue depth of 
0.007 cm as required. The NRC staff is not considering any changes to 
this requirement. For most areas of the body the specified depth 
defines the most radiosensitive tissue or leads to a conservative dose 
calculation if the sensitive tissue is deeper. Calculation of SDE at a 
depth of 0.007 cm is considered an important component of an acceptable 
radiation protection program, and will continue to be required to 
demonstrate compliance with the skin and extremity dose limits.
    CORAR proposed that the NRC provide clarification of the limit in 
the event that multiple SDEs were delivered to the same skin area 
during the year. The NRC staff believes that the annual limit of 50 
rems (0.50 Sv), modified by the requirement in Sec. 20.1201(c) that the 
assigned SDE must be for the ``* * * contiguous 10 square centimeters 
of skin receiving the highest exposure,'' makes it clear that multiple 
exposures to the same area during the record year would be additive for 
comparison to the limit. This interpretation is consistent with the 
recommendations stated in NCRP Statement No. 9, ``Extension of the Skin 
Dose Limit for Hot Particles to Other External Sources of Skin 
Irradiation'' (March 30, 2001).
    An individual commenter, a certified health physicist, noted the 
need to revise the whole-body limits specified in 10 CFR part 20 to use 
effective-dose equivalent (EDE) rather than deep-dose equivalent (DDE). 
The commenter suggested that the risk associated with the DDE from a 
DRP at 1 centimeter was not comparable to the risk associated with DDE 
to the whole body. The NRC staff agrees that consideration should be 
given to adopting the EDE concept in its system of dose limitation. 
However, that issue is not relevant to the rule changes addressed in 
this final rule. The skin dose limit concerns only SDE, and the 
assertion that the associated DDE has minimal stochastic risk would be 
even more accurate if an EDE were used. The rule, as promulgated, is 
believed to reduce unnecessary regulatory burden, while providing 
increased worker protection. The NRC staff is separately addressing 
questions regarding EDE and the use of weighting factors for 
determining whole-body doses.
    The Nuclear Energy Institute (NEI) solicited comments from its 
industry radiation protection members and submitted a letter of strong 
support for the rulemaking. NEI noted that the rule has a strong 
scientific basis, reflects NCRP recommendations that were based on 
replicated research studies, and incorporates a risk-based approach 
that will permit licensees to select protective measures that optimize 
worker safety. The commenter observed that the rule change is an easily 
implemented simplification that will permit reduction of external 
radiation exposure and result in an overall improvement in worker 
safety.
    NEI noted that the rule would change the way licensees estimate the 
dose to the skin, but would not change existing

[[Page 16301]]

dose reporting requirements and guidance. The NRC staff agrees that no 
changes in reporting requirements are needed to implement this final 
rule.
    Virginia Electric and Power Company (Dominion), Southern California 
Edison, Exelon Nuclear Generation Company, and the Tennessee Valley 
Authority (TVA) submitted letters referencing the NEI submittal and 
expressing strong agreement with NEI's comments and support for the 
rule. The Strategic Teaming and Resource Sharing (STARS) group of 
nuclear power plants also submitted comments supporting the proposed 
rule as published.

III. Summary and Discussion of the Changes

    The Commission is amending Sec. 20.1003, Sec. 20.1201(a)(2)(ii), 
and Sec. 20.1201(c), as follows.

Section 20. 1003--Definitions

    In Sec. 20.1003, ``Definitions'', the definition of SDE is revised 
to delete the words ``averaged over an area of 1 square centimeter.'' 
The purpose of these words was to specify the area over which the dose 
to the skin was to be measured or calculated for comparison to the 
limit. The revision to require averaging over 10 square centimeters for 
measuring and recording SDE is found in Sec. 20.1201(c), along with 
other procedural requirements.

Section 20. 1201--Occupational Dose Limits for Adults

    10 CFR 20.1201, ``Occupational Dose Limits for Adults,'' is changed 
in two places. 10 CFR 20.1201(a)(2)(ii) is changed to clarify that the 
SDE limit of 50 rem (0.5 Sv) is the dose limit to the skin of any 
extremity, as well as the skin of the whole body. The Commission 
believes that this specification makes it clear that the only dose 
limit for the extremities is an SDE limit on the dose delivered at a 
depth of 0.007 cm (7 mg/cm\2\), not a deep dose limit.
    10 CFR 20.1201(c) is amended to specify that the assigned SDE must 
be the dose averaged over the 10 contiguous square centimeters of skin 
receiving the highest exposure.
    Although the NCRP recommended limiting the dose from DRPs in the 
ear and on the eye, the NRC staff believes that these are special cases 
only with respect to measuring or calculating the dose, and that this 
revised skin dose limit, together with the existing limit for dose to 
the lens of the eye, is adequate to control DRP doses to these areas.
    It is also important to note that previously it was considered 
relevant to distinguish between doses from DRPs that were on or off the 
skin. With this final rule, this distinction is only relevant to 
dosimetric considerations, and the proposed limit is independent of 
source or exposure geometry.
    The NRC staff has elected to retain rem and Sievert as the units 
for the skin dose limit. According to data published in reports of the 
International Commission on Radiation Protection (ICRP), the unit for 
dose equivalent, rem (Sv), is acceptable for deterministic effects, 
especially at lower doses. The highest relative biological 
effectiveness (RBE) values for deterministic effects in the skin are 
all less than the Q values, or dose weighting factors that are used to 
convert dose in rads (Gy) to dose equivalent in rem (Sv). The use of 
dose equivalent in rem (Sv) units is conservative and has the advantage 
that all of the dose limits will be in the same units. In addition, 
regulations promulgated by the Department of Energy, use the rem and 
Sievert for SDE.
    NCRP Statement No. 9 referred to NCRP Report No. 130 (1999) for 
guidance on good practices, and recommended that in addition to 
numerical limits, the exposed area of skin should be observed for 4 to 
6 weeks whenever the DRP dose at a depth of 70 m exceeds 10 
rads (0.1 Gy) averaged over the most highly exposed 10 square 
centimeters of skin. The observational level of 10 rads (0.1 Gy) is 
well below the new limit of 50 rem (0.5 Sv), and is essentially 
equivalent to the current skin dose limit, at which no clinically 
significant effects have ever been reported. For those reasons, the 
NRC's final rule does not incorporate the NCRP recommendation for 
medical observation.
    The objective of this rulemaking is to establish a uniform, risk-
informed skin dose limit for all sources of SDE, including DRPs, and 
small area contamination that, while it continues to provide adequate 
protection of workers, trades a higher risk of occurrence of temporary 
effects to the skin, such as reddening, for a reduction in the risk of 
whole-body dose and cancer, allows licensees to reduce whole-body 
exposures and nonradiological health risks such as heat stress to 
workers subject to unnecessary DRP monitoring, and provides a common 
limit for SDE from all external sources of ionizing radiation. The rule 
also reduces the unnecessary regulatory burden on licensees to report 
skin exposures that have insignificant health implications.
    The former statement of the skin and extremity dose limit, along 
with the former definition of SDE, required that skin doses be averaged 
over 1 square centimeter. The new rule requires averaging the SDEs 
delivered to the most highly exposed, contiguous, 10 square 
centimeters. It is important to discuss the consequences of this change 
in the context of different source geometries.
    In the case of large-area exposures of the skin from surface 
contamination or other external sources, areas on the order of 10 
square centimeters or more would be likely to receive a relatively 
uniform dose. There is little difference to be expected in recorded 
doses from the former requirement that would attempt to identify the 
most highly exposed 1 square centimeter and the new approach that would 
require averaging doses to the skin over the most highly exposed, 
adjacent 10 square centimeters. The recorded doses would be identical 
for the large-area (10 square centimeters or more) exposures that form 
the great majority of skin dose events.
    Under the new rule, exposed areas of the skin that are less than 10 
square centimeters are treated in a less restrictive manner. For 
example, a dose of 250 rem (2.5 Sv) to each of 2 square centimeters 
results in a 50-rem (0.5-Sv) SDE when averaged over 10 square 
centimeters. A dose as high as 500 rem (5.0 Sv) will be permitted to 1 
square centimeter and will be recorded as 50 rem (0.5 Sv) when averaged 
over 10 square centimeters. This change effectively permits higher 
doses to small areas of skin than were formerly permitted by the 
regulations.
    Although, as previously noted, the Commission is establishing a 
skin dose limit that in some source geometries is likely to permit more 
frequent occurrence of observable, though transient, deterministic 
effects, it is expected that the less restrictive limit will permit a 
reduction in the overly conservative use of protective clothing and 
other devices intended to prevent contamination and skin doses. As a 
result, workers should experience reduced exposure to nonradiological 
health hazards such as heat stress, and be subject to fewer industrial 
accidents caused by impaired motion. By reducing the overly 
conservative use of protective equipment, work should be performed more 
efficiently. Reduced time in the restricted area is expected, along 
with a concomitant reduction in whole-body dose and stochastic risks. 
The Commission intends this change to reduce overly conservative 
efforts to prevent skin contaminations thereby decreasing stress and 
reducing whole-body doses. Numerous studies of the impacts on worker 
efficiency and safety resulting from the use of protective clothing and 
equipment have been

[[Page 16302]]

published in the journal, Health Physics, in Radiation Protection 
Management, and by the Electric Power Research Institute (EPRI). A 
recent discussion of this issue and specific references can be found in 
NUREG/CR-0041, ``Manual of Respiratory Protection Against Airborne 
Radioactive Material'' (January 2001).
    A final geometry of interest is that where DRPs are on or very near 
the skin, such that a relatively small volume of tissue receives a 
large dose, resulting in cell killing and possible observable breaks in 
the skin. Under the former dose limit, a DRP could deliver 50 rem (0.5 
Sv) to an area of 1 square centimeter that when averaged over 1 square 
centimeter would yield a recorded dose of 50 rem (0.5 Sv). Under the 
new rule, the NCRP-recommended limit, a dose of 500 rem (5.0 Sv) 
delivered to 1 square centimeter, when averaged over 10 square 
centimeters, would yield a recorded dose of 50 rem (0.5 Sv). Thus, for 
DRPs on the skin, and other small area exposures, the rule change is in 
effect a tenfold relaxation of the former limit and may permit some 
increased number of observable, transient deterministic effects to the 
skin. This new limit would be approximately equivalent to the emission 
criterion of 75 Ci-hr that was used in the interim enforcement 
policy stated in IN 90-48. The worst case of 500 rem (5.0 Sv) to 1 
square centimeter is estimated to result in a 50-percent chance of an 
observable but transient erythema, and a 15- to 20-percent chance of an 
observable break in the skin. NRC records include only one DRP dose 
that was calculated to exceed 500 rem (5.0 Sv), and no effects were 
observed in that case.
    On the basis of extensive research performed at BNL and elsewhere, 
the NCRP stated in Report No. 130 that ``if (DRP) exposures are 
maintained below the recommended limits, few, if any, deterministic 
biological effects are expected to be observed, and those effects would 
be transient in nature. If effects from a hot-particle exposure are 
observed, the result is an easily treated medical condition involving 
an extraordinarily small stochastic (cancer) risk. Such occurrences 
would be indicative of the need for improvement in radiation protection 
practices, but should not be compared in seriousness to exceeding 
whole-body exposure limits.'' In other words, the NCRP concluded that 
skin dose from DRPs resulted in relatively insignificant health 
effects, and that it was more important to prevent whole body, external 
exposure that might cause cancer.
    Reactor licensees currently monitor workers frequently during each 
work shift to prevent exceeding the interim 50 rem (0.5 Sv) reporting 
threshold for doses from DRPs. The industry estimates that up to 5 
person-rem (0.05 person-Sv) of whole-body dose per outage could be 
attributed to this monitoring. Workers are brought out of the workplace 
to be monitored, thereby incurring nonproductive exit-entry doses, or 
technicians enter the restricted area to monitor workers for DRPs. The 
new, less restrictive skin dose limit will eliminate the need to 
perform this DRP monitoring during work shifts for all but the highest 
activity DRPs,\1\ especially those having a high gamma component. The 
NRC believes that the possibility of some additional number of 
observable, transient deterministic effects, such as a small break in 
the skin, is justified by the reduction of the whole-body dose and 
stochastic risks associated with monitoring for DRPs.
---------------------------------------------------------------------------

    \1\ For example, one recent event at a nuclear power plant 
involved a \60\Co DRP with an activity of about 75 mCi. The DDE 
estimated from this particle (had it been on the skin) was 
calculated to be about 10 rem/hr per mCi. For particles in this 
activity range, the DDE limit of 5 rem per year can be exceeded in 
less than 1 minute, and the new skin dose limit could be exceeded in 
even less time.
---------------------------------------------------------------------------

    NRC's Radiation Exposure Information Reporting System (REIRS) 
database includes reports of nearly 15,000 individual DRP doses since 
1990. Fewer than 10 have exceeded the current 50-rem (0.5-Sv) reporting 
limit. It is unlikely that this revision of the skin dose limit will 
result in any large increase in the number of DRP doses. The as-low-as-
is-reasonably-achievable (ALARA) principle will continue to apply to 
any occupational doses, so the revised skin dose limit should not 
permit a large number of high DRP doses. It would be unacceptable for a 
licensee to permit large numbers of high DRP exposures on a continuing 
basis without attempting some mitigating procedures or engineering 
controls.
    The Commission believes that the less restrictive limit on dose to 
small areas of skin might permit more observable, transient, 
deterministic effects, but nontheless represents a substantial increase 
in worker protection because reduced use of protective clothing will 
result in a less hazardous workplace and less frequent monitoring for 
DRP contamination will result in reduced whole-body occupational dose. 
This represents a shift in emphasis toward a risk-informed approach 
that would possibly permit more frequent deterministic effects in order 
to avoid the physical stress and whole-body doses associated with 
monitoring workers and the use of protective measures. All of the 
public comments received on the proposed rule supported this tradeoff.

IV. Enforcement

    On July 31, 1990 (55 FR 31113), the Commission published a policy 
statement entitled ``Hot Particle Enforcement Policy,'' presenting 
criteria for enforcement discretion in cases that involve occupational 
skin dose due to radiation exposure from a hot particle. This policy 
was intended to be applicable until 10 CFR part 20 was revised to 
include new limits applicable to these cases. Given that 10 CFR part 20 
is being revised, on the effective date of this rule, this policy will 
no longer be in effect.

V. Issue of Compatibility for Agreement States

    Under the ``Policy Statement on Adequacy and Compatibility of 
Agreement State Programs,'' which became effective on September 3, 1997 
(62 FR 46517), NRC program elements, including regulations, are 
assigned compatibility categories. In addition, NRC program elements 
can also be identified as having particular health and safety 
significance or as being reserved solely to the NRC.
    Compatibility Category A includes those program elements that are 
basic radiation protection standards and scientific terms and 
definitions that are necessary to understand radiation protection 
concepts. An Agreement State should adopt Category A program elements 
in an essentially identical manner in order to provide uniformity in 
the regulation of agreement material on a nationwide basis.
    Compatibility Category B includes those program elements that apply 
to activities that have direct and significant effects in multiple 
jurisdictions. An Agreement State should adopt Category B program 
elements in an essentially identical manner.
    Compatibility Category C includes those program elements that do 
not meet the criteria of Category A or B but represent essential 
objectives that an Agreement State should adopt to avoid conflict, 
duplication, gaps, or other conditions that would jeopardize an orderly 
pattern in the regulation of agreement material on a nationwide basis. 
An Agreement State should adopt the essential objectives of the 
Category C program elements.
    Compatibility Category D includes those program elements that do 
not meet any of the criteria of Category A, B, or C above and, thus, do 
not need to

[[Page 16303]]

be adopted by Agreement States for purposes of compatibility.
    Health and Safety (H&S) includes program elements that are not 
required for compatibility (i.e., Category D), but that have been 
identified as having a particular health and safety role (i.e., 
adequacy) in the regulation of agreement material within the State. 
Although not required for compatibility, the State should adopt program 
elements in this category that embody the essential objectives of the 
NRC program elements because of particular health and safety 
considerations.
    Compatibility Category NRC includes those program elements that 
address areas of regulation that cannot be relinquished to Agreement 
States pursuant to the Atomic Energy Act (AEA) or provisions of Title 
10 of the Code of Federal Regulations. These program elements should 
not be adopted by Agreement States.
    The modifications to Secs. 20.1003 and 20.1201, which contain 
definitions and basic radiation protection standards that are necessary 
to understand radiation protection concepts, are designated as 
compatibility Category A. Therefore, the Agreement State program 
element should be essentially identical to the NRC's in order to ensure 
uniformity in skin dose determinations on a nationwide basis.
    The proposed amendments and compatibility determinations were 
provided to the States for review and comment. No comments were 
received objecting to the new rule or the compatibility determinations.

VI. Voluntary Consensus Standards

    The National Technology Transfer and Advancement Act of 1995, 
Public Law 104-113, requires that Federal agencies use technical 
standards that are developed or adopted by voluntary consensus 
standards bodies unless using such a standard is inconsistent with 
applicable law or is otherwise impractical. In this rule, the NRC is 
amending its definition of SDE. This action does not constitute the 
establishment of a standard that contains generally applicable 
requirements. The NRC is, however, adopting the recommendations of the 
NCRP regarding acceptable limits on radiation dose to the skin of 
occupationally exposed workers.

VII. Environmental Assessment: Finding of No Significant 
Environmental Impact: Availability

    The NRC has determined under the National Environmental Policy Act 
of 1969, as amended, and the Commission's regulations in subpart A of 
10 CFR part 51 that this amendment is not a major Federal action 
significantly affecting the quality of the human environment and, 
therefore, an environmental impact statement is not required.
    An environmental assessment has determined that the amendment 
addresses technical and procedural improvements in the provisions for 
measuring or calculating the dose to the skin for comparison to the 
skin dose limit for the whole body or for the extremities. None of the 
impacts associated with this rulemaking have any effect on any places 
or entities outside of a licensed site. This rulemaking is expected to 
decrease the need for use of protective equipment by nuclear power 
plant workers and others who are potentially exposed to skin 
contamination. No changes are expected in existing licensee programs 
and procedures designed to mitigate the production and spread of DRPs 
in the workplace and to prevent the unauthorized release of radioactive 
materials off site. It is expected that there will be no change in 
radiation dose to any member of the public as a result of the revised 
regulation. The amendment is expected to result in a reduction in 
external occupational dose to workers onsite. The determination of this 
environmental assessment is that there will be no significant offsite 
impact to the public from this action. The NRC requested public 
comments and the views of the States on the environmental assessment 
for this rule. No comments were received that addressed changes to the 
environmental assessment.
    The environmental assessment is available for inspection in the 
NRC's Public Document Room, One White Flint North, 11555 Rockville Pike 
(first floor), Rockville, Maryland.

VIII. Paperwork Reduction Act Statement

    This final rule decreases the burden on licensees reporting under 
Sec. 20.2202(b)(iii) on discrete radioactive particles and other small 
area skin overexposures. The burden reduction for this information 
collection is estimated to average 40 hours per report. Fewer than 10 
reports have been received by the NRC over the past 12 years. Licensees 
must also revise policies and procedures for measuring discrete 
radioactive particles. The burden for these revisions is estimated to 
average .5 hours per power reactor licensee. Because the burden for 
these information collection changes is insignificant, Office of 
Management and Budget (OMB) clearance is not required. Existing 
requirements were approved by the Office of Management and Budget, 
approval number 3150-0014.

Public Protection Notification

    If a means used to impose an information collection does not 
display a currently valid OMB control number, the NRC may not conduct 
or sponsor, and a person is not required to respond to, the information 
collection.

IX. Regulatory Analysis

    The NRC has prepared a regulatory analysis for this amendment. The 
analysis examines the benefits and impacts considered by the NRC. The 
regulatory analysis is available for inspection in the NRC Public 
Document Room, One White Flint North, 11555 Rockville Pike (first 
floor), Rockville, Maryland.

X. Regulatory Flexibility Certification

    As required by the Regulatory Flexibility Act of 1980, 5 U.S.C. 
605(b), the Commission certifies that this rule will not have a 
significant economic impact on a substantial number of small entities. 
The anticipated impact of the changes will not be significant because 
the revised regulation essentially represents a continuation of current 
practice. The benefits of the rule are that it permits averaging doses 
to the skin over the most highly exposed 10 square centimeters, 
incorporates an NCRP recommendation for a less-restrictive skin dose 
limiting procedure, and permits reduced use of protective equipment 
known to expose workers to workplace stresses and unnecessary whole-
body radiation dose.

XI. Backfit Analysis

    Although the NRC has concluded that this amendment constitutes a 
reduction in unnecessary regulatory burden, the implementation of these 
changes will require revisions to licensee procedures, thereby 
constituting a potential backfit under 10 CFR 50.109(a)(1). Under 
Sec. 50.109(a)(2), a backfit analysis is required unless the rule meets 
one of the exceptions listed in Sec. 50.109(a)(4). This rule meets the 
exception at Sec. 50.109(a)(4)(iii) in that it redefines the level of 
adequate protection embodied in the occupational dose limit for doses 
to the skin of the whole body and to the skin of the extremities. In 
addition, implementation of this rule is expected to increase 
industrial safety for workers substantially.
    Section III, Summary and Discussion of the Changes, discusses the 
changes to the definition of SDE and the provision for averaging SDE 
over the most highly exposed 10 square centimeters. This

[[Page 16304]]

change raises the skin dose limit for DRPs on or near the skin and for 
small-area ( 1.0 square centimeter) contaminations. This change makes 
it possible for licensees to measure or calculate skin doses for 
comparison to the 50-rem (0.5-Sv) limit that, when averaged over 10 
square centimeters, result in dose values that more appropriately 
reflect the risk associated with small area exposures according to the 
NCRP. The increased limit in the case of DRPs will eliminate the need 
to frequently monitor workers for DRP contamination during work shifts 
for all but the highest activity DRPs, especially those having a high 
gamma component. This reduced monitoring will eliminate most of the 
whole-body dose and stochastic risk associated with monitoring to avoid 
exceeding the former, more restrictive skin dose limit. In addition, 
the relaxed skin dose limit, based on NCRP recommendations, should 
clarify that the consequences of transient skin contamination are less 
significant than the radiological and nonradiological risks that 
workers incur as a result of licensees' efforts to avoid skin 
contamination. The overly conservative use of multiple layers of 
protective clothing and other devices worn to prevent skin 
contamination cause exposure to nonradiological hazards such as heat 
stress, as well as a reduction in worker efficiency estimated by 
industry to be as much as 15 to 25 percent, which, in turn, increases 
whole-body dose. With the new rule licensees will be able to choose to 
use less protective gear at the cost of more frequent skin 
contamination, but with the benefit of less physical stress and reduced 
whole-body dose to workers.
    The 1991 Federal Register Notice of final rulemaking on 10 CFR Part 
20 (56 FR 23360; May 21, 1991) made it clear that the skin dose limit 
would be addressed in subsequent rulemaking. The Commission also said 
that even had the 1991 changes, primarily to dose limits, not 
contributed to substantial increase in occupational health and safety, 
such changes would also amount to a redefinition of the level of 
adequate protection. This change in the skin and extremity dose limit 
will reduce worker exposure to external dose and the associated cancer 
risks, and reduce worker exposure to non-radiological hazards imposed 
by use of overly conservative protective equipment.
    In conclusion, the Commission believes that this rule change 
constitutes a reduction in unnecessary regulatory burden, redefines the 
level of adequate protection, and should substantially increase worker 
safety. The changes, therefore, do not require a backfit analysis under 
Sec. 50.109(a)(4)(iii).

XII. Small Business Regulatory Enforcement Fairness Act

    In accordance with the Small Business Regulatory Enforcement 
Fairness Act of 1996, the NRC has determined that this action is not a 
major rule and has verified this determination with the Office of 
Information and Regulatory Affairs of OMB.

List of Subjects in 10 CFR Part 20

    Byproduct material, Licensed material, Nuclear materials, Nuclear 
power plants and reactors, Occupational safety and health, Packaging 
and containers, Penalty, Radiation protection, Reporting and recording 
requirements, Source material, Special nuclear material, Waste 
treatment and disposal.


    For the reasons set out in the preamble and under the authority of 
the Atomic Energy Act of 1954, as amended; the Energy Reorganization 
Act of 1974, as amended; and 5 U.S.C. 552 and 553; the NRC is adopting 
the following amendments to 10 CFR part 20.

PART 20--STANDARDS FOR PROTECTION AGAINST RADIATION

    1. The authority citation for part 20 continues to read as follows:

    Authority: Secs. 53, 63, 65, 81, 103, 104, 161, 182, 186, 68 
Stat. 930, 933, 935, 936, 937, 948, 953, 955, as amended, Sec. 1701, 
106 Stat. 2951, 2952, 2953 (42 U.S.C. 2073, 2093, 2095, 2111, 2133, 
2134, 2201, 2232, 2236, 2297f), Secs. 201, as amended, 202, 206, 88 
Stat. 1242, as amended, 1244, 1246 (42 U.S.C. 5841, 5842, 5846).


    2. In Sec. 20.1003 the definition of Shallow-dose equivalent 
(Hs is revised to read as follows:


Sec. 20.1003  Definitions

* * * * *
    Shallow-dose equivalent (Hs), which applies to the 
external exposure of the skin of the whole body or the skin of an 
extremity, is taken as the dose equivalent at a tissue depth of 0.007 
centimeter (7 mg/cm2).
* * * * *

    3. In Sec. 20.1201 the introductory text of paragraph (a)(2), and 
paragraphs (a)(2)(ii) and (c), are revised to read as follows:


Sec. 20.1201  Occupational Dose Limits for Adults

    (a) * * *
    (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:
* * * * *
    (ii) A shallow-dose equivalent of 50 rem (0.5 Sv) to the skin of 
the whole body or to the skin of any extremity.
* * * * *
    (c) The assigned deep-dose equivalent must be for the part of the 
body receiving the highest exposure. The assigned shallow-dose 
equivalent must 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.
* * * * *

    Dated at Rockville, Maryland, this 1st day of April, 2002.

    For the Nuclear Regulatory Commission.
Annette L. Vietti-Cook,
Secretary of the Commission.
[FR Doc. 02-8246 Filed 4-4-02; 8:45 am]
BILLING CODE 7590-01-P