[Federal Register Volume 67, Number 181 (Wednesday, September 18, 2002)]
[Notices]
[Pages 58826-58829]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-23691]


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NUCLEAR REGULATORY COMMISSION

[Docket Nos. 50-313, 368, 416, 003, 247, 286, 333, 293, 458, 271, and 
382]


Entergy Operations, Inc., Entergy Nuclear Operations, Inc., 
Arkansas Nuclear One, Units 1 and 2; Grand Gulf Nuclear Station; Indian 
Point Nuclear Station, Units 1, 2 and 3; James A. Fitzpatrick Nuclear 
Power Plant; Pilgrim Nuclear Power Station; River Bend Station; Vermont 
Yankee Nuclear Power Plant; and Waterford Steam Electric Station, Unit 
3; Exemption

1.0 Background

    Entergy Operations, Inc. and Entergy Nuclear Operations, Inc. (the 
licensees) are the holders of Renewed Facility Operating License No. 
DPR-51; Facility Operating License Nos. NPF-6 and NPF-29; Provisional 
Operating License No. DPR-5; and Facility Operating License Nos. DPR-
26, DPR-64, DPR-59, DPR-35, NPF-47, DPR-28, and NPF-38, which authorize 
operation of Arkansas Nuclear One, Units 1 and 2; Grand Gulf Nuclear 
Station; Indian Point Nuclear Station, Units 1, 2 and 3; James A. 
Fitzpatrick Nuclear Power Plant; Pilgrim Nuclear Power Station; River 
Bend Station; Vermont Yankee Nuclear Power Plant; and Waterford Steam 
Electric Station, Unit 3. The licenses provide, among other things, 
that the facilities are subject to all rules, regulations, and orders 
of the U.S. Nuclear Regulatory Commission (NRC, the Commission) now or 
hereafter in effect.
    The facilities consist of pressurized and boiling water reactors 
located in Pope County, Arkansas; Claiborne County, Mississippi; 
Westchester County, New York; Oswego County, New York; Plymouth County, 
Massachusetts; West Felciana Parish, Louisiana; Windham County, 
Vermont; and Saint Charles Parish, Louisiana. (The operating authority 
of Provisional Operating License No. DPR-5 for Indian Point Nuclear 
Station, Unit 1, was revoked by Commission Order dated June 19, 1980).

[[Page 58827]]

2.0 Request/Action

    Title 10 of the Code of Federal Regulations (10 CFR), Part 20, 
Section 20.1003 states that the definition of total effective dose 
equivalent (TEDE) is the sum of the deep-dose equivalent (for external 
exposures) and the committed effective dose equivalent (for internal 
exposures). The proposed exemption would change the definition of TEDE 
to mean the sum of the effective dose equivalent or the deep-dose 
equivalent (for external exposures) and the committed effective dose 
equivalent (for internal exposures). The licensee requests the 
exemption because the current method of calculating TEDE, under certain 
conditions, can significantly overestimate the dose received.
    In summary, the licensee's application dated July 20, 2001, as 
supplemented by letter dated June 13, 2002, requests an exemption from 
the 10 CFR 20.1003 definition of TEDE.

3.0 Discussion

    Pursuant to 10 CFR 20.2301, the Commission may, upon application by 
a licensee or upon its own initiative, grant exemptions from the 
requirements of 10 CFR Part 20 if it determines the exemptions are 
authorized by law and would not result in undue hazard to life or 
property.
    The staff examined the licensee's rationale to support the 
exemption request and concluded that the new method for calculating 
TEDE, under certain conditions, is a more accurate means of estimating 
worker radiation exposure and therefore would not result in undue 
hazard to the workers. The basis for this is as follows.

4.0 Regulatory Evaluation

    By letter dated July 20, 2001, as supplemented by letter dated June 
13, 2002, the licensee requested an exemption from the current 
definition, and the approval to use an alternate definition, of TEDE in 
10 CFR 20.1003. The licensee requested that the definition of TEDE, as 
used in 10 CFR 20.1003 (i.e., for the purpose of complying with the 
dose recording requirements, dose reporting requirements, or the dose 
limits), be changed to mean the sum of the effective dose equivalent or 
the deep dose equivalent (for external exposures), and the committed 
effective dose equivalent (for internal exposures). The licensee also 
requested approval to use a method for estimating the effective dose 
equivalent for external exposures (EDEex) published by the 
Electric Power Research Institute (EPRI) in Technical Report TR-101909, 
Volumes 1 and 2, and the Implementation Guide TR-109446. (These EPRI 
documents were provided on the docket as enclosures to a previous May 
1, 2001, application from the licensee, which was superseded by the 
July 20, 2001, application). The effect of granting this request would 
be to allow the licensee the option to control TEDE using 
EDEex in those cases where it is a more accurate predictor 
of the risk from occupational radiation exposure.
    The radiation protection approach and dose limits contained in 10 
CFR Part 20 are based on the recommendations of the International 
Commission on Radiation Protection (ICRP) in their 1977 publication No. 
26 (ICRP 26). For stochastic effects, the ICRP-recommended dose 
limitation is based on the principle that the risk should be equal, 
whether the whole body is irradiated uniformly or whether there is non-
uniform irradiation (such as when radioactive materials are taken into 
the body and, depending on their physical and chemical properties, 
concentrate in certain tissues and organs). This condition will be met 
if

[]T[
]THT<=Hwb,L

where []T is a 
weighting factor representing the proportions of the stochastic risk 
resulting from tissue (T) to the total risk, when the whole body is 
irradiated uniformly; HT is the annual dose equivalent in 
tissue (T); and Hwb.L is the recommended annual dose-
equivalent limit for uniform irradiation of the whole body, namely 5 
rem (50 mSv). The sum 
[]T[
]THT is called 
effective dose equivalent (EDE). The values for 
[]T are given 
in ICRP 26, for the various tissues (T), and are codified in 10 CFR 
Part 20.
    For the purposes of implementing workplace controls, and due to the 
difference in dosimetry, 10 CFR Part 20 breaks this total EDE, or TEDE, 
into two components: (1) Dose resulting from radioactive sources 
internal to the body, and (2) dose resulting from sources external to 
the body. For radioactive material taken into the body, the 
occupational dose limit is based on the resulting dose equivalent 
integrated over 50 years (H50) of exposure such that

[]T[
]TH50,T<=Hwb,L


This quantity 
[]T[
]TH50,T is called the 
Committed Effective Dose Equivalent (CEDE) in 10 CFR Part 20.
    Demonstrating compliance with the dose limits from internal 
exposures is accomplished using direct measurements of concentrations 
of radioactivity in the air in the work areas, or quantities of 
radionuclides in the body, or quantities of radionuclides excreted from 
the body, or a combination of these. Having determined the quantities 
of radionuclides present or taken into the body, these can be compared 
to secondary or tertiary limits (e.g., Annual Limits on Intake or 
Derived Air Concentrations) listed in Appendix B to 10 CFR Part 20. 
These secondary and tertiary limits have been calculated using standard 
assumptions of the physical and chemical forms of the radionuclides, 
the standard physiological parameters from the Reference Man, and the 
bio-kinetic models adopted in ICRP 26. Alternatively, the regulations 
allow the licensee to adjust certain of these standard assumptions and 
calculate CEDE directly, using appropriate models.
    The common practice for determining radiation dose from external 
sources is to measure the radiation intensity at the surface of the 
body with a monitoring device (dosimeter) calibrated to read in terms 
of a tissue dose equivalent at a specified tissue depth. In 1991, when 
10 CFR Part 20 was revised to adopt the ICRP 26 recommendations on 
limits and controls, there was little guidance on how to determine the 
dose to the several tissues necessary to calculate EDEex. It 
is impractical to separately monitor (or measure) the dose received by 
the various organs and tissues that contribute to TEDE. As a practical, 
conservative simplification, 10 CFR Part 20 limits the dose from 
external sources in terms of Deep Dose Equivalent (DDE). The DDE is the 
dose equivalent at a tissue depth of one centimeter, and is required 
(by 10 CFR Part 20.1201(c)) to be determined for the part of the body 
receiving the highest exposure. The TEDE annual limit is met if

DDE + 
[]T[
]TH50,T <= 5 rem (50 
mSv).

In addition to the annual limit on TEDE, 10 CFR Part 20 provides a non-
stochastic annual limit of 50 rem (0.5 Sv) for each individual tissue 
such that

DDE + H50,T <= 50 rem (0.50 Sv)

for all tissues except the skin and lens of the eye.
    Using the highest DDE, to bound the individual tissue doses from 
radioactive sources outside the body, generally results in a slightly 
conservative estimate of EDEex from uniform exposures; 
however, it can be overly conservative for non-uniform exposure 
situations. Since many high-dose jobs at nuclear power plants are 
performed under non-uniform exposure conditions, this can lead to a 
significant overestimation of the actual TEDE dose, and the risk, to 
the workers. To address this issue, the licensee has requested

[[Page 58828]]

approval to provide a more accurate dose assessment by replacing DDE 
with EDEex when calculating TEDE from non-uniform exposures, 
where the EDEex is determined with a method developed by the 
EPRI.
    In developing this method, the EPRI investigators used mathematical 
equations developed by Cristy and Eckerman to model standard, adult 
human male and female subjects (phantoms). The Monte Carlo radiation 
transport computer code MCNP was used to calculate the dose to 
individual tissues modeled in the phantoms, and simulated dosimeter 
readings, for a range of different exposure geometries. Dosimeters with 
an isotropic response were modeled at several locations on the surface 
of the phantoms. Both broad beam and point radiation sources (with 
selected photon energies) were considered. Indicated doses (e.g., 
simulated dosimeter readings) and the actual EDEex (e.g., 
the sum of the products of the calculated phantom tissue doses and 
their respective ICRP 26 weighting factors) were calculated for photons 
incident on the phantoms from various locations. Empirical algorithms 
were developed to relate the EDEex resulting from the full 
range of exposure situations to the indicated doses that could be 
measured at the surface of the body. Two algorithms were developed to 
estimate EDEex from just two dosimeters worn on the trunk of 
the whole body (front and back, respectively). The first algorithm is a 
simple, non-weighted averaging of the front and back dosimeter 
readings. The second algorithm weights the higher of the two dosimeter 
readings.

5.0 Technical Evaluation

    The staff reviewed the technical descriptions of the EPRI method 
for estimating EDEex; the resulting data and conclusions 
contained in Technical Report TR-101909, Volumes 1 and 2; the 
Implementation Guide TR-109446; and supporting technical papers 
published by the principal EPRI investigators. The staff also performed 
independent calculations to verify a sampling of the results tabulated 
in these documents.
    Table 8 in TR-101909, Volume 2, provides a summary of the 
EDEex and dosimeter (front and back) readings calculated for 
parallel beams and point sources used to develop the EPRI algorithms. 
The staff noted that the magnitude of the units for the parallel beam 
dose factors listed in Table 8 are low by five orders of magnitude 
(e.g., ``E-15 rad-cm squared per photon'' instead of the correct ``E-10 
rad-cm squared per photon''). The licensee verified, in its June 13, 
2002, supplemental letter, that this is a typographical error in the 
EPRI document. However, this error does not affect the conclusions 
drawn from the data. The licensee has stated that they will not use the 
specific dose factors listed in Table 8 to calculate EDEex.
    The EPRI work indicates that a single dosimeter (calibrated to read 
DDE) worn on the chest provides a reasonably accurate estimate of 
EDEex when the individual is exposed to a number of randomly 
distributed radiation sources during the monitoring period. This is 
consistent with current allowable dosimetry practices and requires no 
special approval. The alternate definition of TEDE requested would 
allow the licensee the option to monitor worker dose with a single DDE 
measurement, as currently required, or to control TEDE using 
EDEex (as determined by the EPRI two-badge method). This 
would benefit the licensee in situations where monitoring the highest 
DDE would require moving or supplementing the single badge.
    The data presented in the EPRI reports indicate that the weighted, 
two-dosimeter algorithm provides a reasonably conservative estimate of 
EDEex. However, the non-weighted algorithm does not always 
give a conservative result. The licensee has stated that it will only 
use the weighted, two-dosimeter algorithm such that

EDEex = \1/2\ (MAX + \1/2\ (Rfront + 
Rback))

where Rfront is the reading of the dosimeter on the front of 
the body, Rback is the reading of the dosimeter on the back 
of the body, and MAX is the higher of the front or back dosimeter 
readings.
    Additional issues and limitations noted in the staff's review are 
included in the following paragraphs.
    Partial-body irradiations that preferentially shield the dosimeter 
could bias the EPRI method results in the non-conservative direction. 
The licensee has stated that they will ensure that the dosimeters are 
worn so that at least one of the two badges ``sees'' the source(s) of 
radiation. In other words, the radiological work will be conducted and 
the dosimeters worn in such a way, so that no shielding material is 
present between the radioactive source(s) and the whole body, that 
would cast a shadow on the dosimeter(s) and not over other portions of 
the whole body.
    Isotropic dosimeters (e.g., dosimeters that respond independently 
of the angle of the incident radiation) are impractical and not widely 
available commercially. Therefore, the licensee must implement the EPRI 
method using dosimeters that will have an angular-dependent response. 
If the dosimeter reading decreases more rapidly than EDEex, 
with increasing exposure angle, the resulting EDEex estimate 
will be biased in the non-conservative direction. The EPRI principle 
investigators have addressed this issue of angular dependance in their 
published technical paper entitled, ``A Study of the Angular Dependence 
Problem In Effective Dose Equivalent Assessment'' (Health Physics 
Volume 68. No. 2, February 1995, pp. 214-224). The licensee has stated 
that the dosimeters used to estimate EDEex will have 
demonstrated angular response characteristics at least as good as that 
specified in this technical paper. In addition, the dosimeters will be 
calibrated to indicate DDE at the monitored location, to ensure their 
readings reflect electronic equilibrium conditions.
    The EPRI method for estimating EDEex from two dosimeter 
readings is not applicable to exposure situations where the sources of 
radiation are nearer than 12 inches (30 cm) from the surface of the 
body. Tables 5 thru 7 in EPRI TR-101909, Volume 2, provide calculated 
EDEex values resulting from exposure to point sources in 
contact with the torso of the body. However, the staff review 
determined that the information provided in these tables does not bound 
all of the pertinent point source exposure situations. The licensee has 
stated that the use of EDEex to determine compliance with 
the TEDE limit, resulting from point sources (i.e., hot particles) on 
or near the surface of the body, is outside the scope of this request.
    The exemption applies only to the TEDE definition and calculations. 
It does not modify the dose limits for any individual organ or tissue 
specified in, or method for complying with, 10 CFR Part 20. Also, when 
DDE is used to calculate TEDE under the revised definition, the 
requirement that it be for the part of the body receiving the highest 
exposure in 10 CFR 20.1201(c) is applicable.

6.0 Evaluation Summary

    The staff concludes that calculating TEDE using this 
EDEex in place of DDE provides a more accurate estimate of 
the risk associated with the radiation exposures experienced by 
radiation workers at a nuclear power plant. Additionally the staff 
finds that the proposal to limit TEDE such that

EDEex + CEDE <= 5 rem

is consistent with the basis for the limits in 10 CFR Part 20. 
Therefore, subject to the limitations noted above, defining TEDE to 
mean the sum of EDEex or DDE

[[Page 58829]]

(for external exposures) and CEDE (for internal exposures), in lieu of 
the current 10 CFR 20.1003 definition, is acceptable.
    Additionally, the staff concludes that the methods for estimating 
EDEex described in EPRI Technical Report TR-101909, Volumes 
1 and 2, and Implementation Guide TR-109446 are based on sound 
technical principles. The proposed EPRI weighted, two-dosimeter 
algorithm provides an acceptably conservative estimate of 
EDEex with a degree of certainty that is comparable to that 
inherent in the methods allowed by 10 CFR Part 20 for estimating CEDE. 
Therefore, subject to the limitations noted above, using the EPRI 
weighted, two-dosimeter algorithm so that

EDEex = \1/2\ (MAX + \1/2\ (Rfront + 
Rback))

for the purposes of demonstrating compliance with 10 CFR 20.1003 is 
acceptable.

7.0 Conclusion

    Accordingly, the Commission has determined that, pursuant to 10 CFR 
20.2301, the exemption is authorized by law and would not result in 
undue hazard to life or property. Therefore, the Commission hereby 
grants Entergy Operations, Inc. and Entergy Nuclear Operations, Inc. an 
exemption from the requirements of 10 CFR 20.1003 for Arkansas Nuclear 
One, Units 1 and 2; Grand Gulf Nuclear Station; Indian Point Nuclear 
Station, Units 1, 2 and 3; James A. Fitzpatrick Nuclear Power Plant; 
Pilgrim Nuclear Power Station; River Bend Station; Vermont Yankee 
Nuclear Power Plant; and Waterford Steam Electric Station, Unit 3. The 
exemption changes the definition of TEDE to mean the sum of 
EDEex or DDE (for external exposures) and CEDE (for internal 
exposures). This Exemption is granted to allow the licensee the option 
to monitor worker dose using EDEex based on the following 
conditions:
    1. Only the EPRI weighted, two-dosimeter algorithm will be used 
such that

EDEex = \1/2\ (MAX + \1/2\ (Rfront + 
Rback))

where Rfront is the reading of the dosimeter on the front of 
the body, Rback is the reading of the dosimeter on the back 
of the body, and MAX is the higher of the front or back dosimeter 
readings.
    2. The radiological work will be conducted and the dosimeters worn 
in such a way, so that no shielding material is present between the 
radioactive source(s) and the whole body, that would cast a shadow on 
the dosimeter(s) and not over other portions of the whole body.
    3. The dosimeters used to estimate EDEex will have 
demonstrated angular response characteristics at least as good as that 
specified in the technical paper entitled, ``A Study of the Angular 
Dependence Problem In Effective Dose Equivalent Assessment'' (Health 
Physics Volume 68. No. 2, February 1995, pp. 214-224). Also, the 
dosimeters will be calibrated to indicate DDE at the monitored 
location, to ensure their readings reflect electronic equilibrium 
conditions.
    4. The EPRI method for estimating EDEex from two 
dosimeter readings is not applicable to exposure situations where the 
sources of radiation are nearer than 12 inches (30 cm) from the surface 
of the body.
    Pursuant to 10 CFR 51.32, the Commission has determined that the 
granting of this exemption will not have a significant effect on the 
quality of the human environment (67 FR 56603, dated September 4, 
2002).
    This exemption is effective upon issuance.

    Dated at Rockville, Maryland, this 12th day of September 2002.

    For the Nuclear Regulatory Commission.
Bruce A. Boger,
Director, Division of Inspection Program Management, Office of Nuclear 
Reactor Regulation.
[FR Doc. 02-23691 Filed 9-17-02; 8:45 am]
BILLING CODE 7590-01-P