[Federal Register Volume 71, Number 34 (Tuesday, February 21, 2006)]
[Notices]
[Pages 8854-8856]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E6-2405]


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ENVIRONMENTAL PROTECTION AGENCY

[EPA-HQ-OAR-2002-2005; FRL-8034-3]


National Emission Standards for Hazardous Air Pollutants 
(Radionuclides), Availability of Updated Compliance Model

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of availability.

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SUMMARY: Pursuant to section 112 of the Clean Air Act, the 
Environmental Protection Agency is announcing the availability of 
Version 3 of the CAP88-PC model used to demonstrate compliance with the 
National Emission Standards for Hazardous Air Pollutants (NESHAPs) 
applicable to radionuclides. CAP88-PC is approved for this use by EPA. 
Version 3 includes an expanded library of radionuclides and 
incorporates updated radionuclide risk conversion factors. Hence, it is 
recommended that Version 3 be used for future compliance 
demonstrations.

FOR FURTHER INFORMATION CONTACT: Behram Shroff, Office of Radiation and 
Indoor Air, Radiation Protection Division (6608J), U.S. Environmental 
Protection Agency, 1200 Pennsylvania Ave., NW, Washington, DC 20460-
0001; telephone number: (202) 343-9707; fax number: (202) 343-2304; e-
mail address: [email protected].

SUPPLEMENTARY INFORMATION: 

I. General Information

A. Does This Action Apply to Me?

    You may be potentially affected by this action if you are subject 
to the reporting requirements for radionuclide NESHAPs found in 40 CFR 
part 61, subpart H. This subpart applies to Department of Energy (DOE) 
facilities.

B. How Can I Get Copies of the Model and Related Information?

    1. Docket. EPA has established a docket for this action under 
Docket ID No. EPA-HQ-OAR-2002-0050; FRL-XXXX-X. Publicly available 
docket materials are available either electronically through http://www.regulations.gov or in hard copy at the Air and Radiation Docket in 
the EPA Docket Center (EPA/DC), EPA West, Room B102, 1301 Constitution 
Ave., NW., Washington, DC. The EPA Docket Center Public Reading Room is 
open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding 
legal holidays. The telephone number for the Public Reading Room is 
(202) 566-1744, and the telephone number for the Air and Radiation 
Docket is (202) 566-1742.
    2. Electronic Access. You may access this Federal Register document 
electronically through the EPA Internet under the ``Federal Register'' 
listings at http://www.epa.gov/fedrgstr/.
    3. EPA Web site. You may download the CAP88-PC model and 
documentation from EPA's Web site at http://www.epa.gov/radiation/assessment/CAP88/index.html.

II. Background

    On October 31, 1989, EPA promulgated the National Emissions 
Standards for Hazardous Air Pollutants (NESHAPs) under Section 112 of 
the Clean Air Act to control radionuclide emissions to the ambient air 
from a number of different source categories (54 FR 51654, December 15, 
1989 (Docket EPA-HQ-OAR-2002-0050, Item 0028)). Subpart H of 40 CFR 
part 61 is one of the source categories covered in this 1989 final 
rule. Facilities owned and operated by the Department of Energy (DOE) 
are covered by subpart H. DOE administers many facilities, including 
government-owned, contractor-operated facilities across the country. 
Some of these DOE facilities handle significant amounts of radioactive 
material and can emit radionuclides into the air in various physical 
and chemical states. The purpose of subpart H is to limit radionuclide 
emissions (not including radon) from the stacks and vents at DOE 
facilities so that no member of the public receives an effective dose 
equivalent of more than 10 millirem per year (mrem/yr).

III. CAP88-PC Model for Demonstrating Compliance

A. CAP88-PC Model History

    EPA is today announcing the availability of Version 3 of the CAP88-
PC model for use in demonstrating compliance with the requirements of 
40 CFR part 61, subpart H. CAP88 (Clean Air Act Assessment Package--
1988) (Docket EPA-HQ-OAR-2002-0050, Items 0033 through 0036) is a set 
of computer programs, databases and associated utility programs for 
estimation of dose and risk from radionuclide emissions to air. CAP88-
PC implements, on the personal computer platform, modified versions of 
the AIRDOS-EPA and DARTAB codes that were written in FORTRAN 77 and 
executed in a mainframe computing environment. CAP88-PC provides for 
dose and risk assessments of collective populations, maximally-exposed 
individuals, and selected individuals. The complete set of dose and 
risk factors is provided.
    The original CAP88-PC software package, Version 1.0 (Docket EPA-HQ-
OAR-2002-0050, Items 0040 and 0041), allowed users to perform full-
featured dose and risk assessments in a DOS environment for the purpose 
of demonstrating compliance with 40 CFR 61.93(a); it was approved for 
compliance demonstration in February 1992.
    CAP88-PC Version 2.0 (Docket EPA-HQ-OAR-2002-0050, Items 0042 and 
0043) provided a framework for developing inputs to perform full-
featured dose and risk assessments in a Windows environment for the 
purpose of demonstrating compliance with 40 CFR 61.93(a). Version 2.0 
was approved for compliance demonstration in 1999. Version 2.1 included 
some additional changes compared to the DOS version and the previous 
Windows version, 2.0.

[[Page 8855]]

The changes included the addition of more decay chains, improvements in 
the Windows code error handling, and a modified nuclide data input 
form. Section 1.6 of the CAP88-PC Version 3 User's Guide (Docket EPA-
HQ-OAR-2002-0050, Item 0047) provides a summary of the changes 
incorporated into Version 2.1 relative to Version 2.0.
    CAP88-PC Version 3.0 is a significant update to Version 2.1. 
Version 3 incorporates dose and risk factors from Federal Guidance 
Report 13, ``Cancer Risk Coefficients for Environmental Exposure to 
Radionuclides'' (FGR 13, Docket EPA-HQ-OAR-2002-0050, Items 0037 
through 0039, also available at http://www.epa.gov/radiation/federal/techdocs.htm), in place of the RADRISK data that was used in previous 
versions. The FGR 13 factors are based on the methods in Publication 72 
of the International Commission on Radiological Protection (ICRP), 
``Age-Dependent Doses to Members of the Public from Intake of 
Radionuclides''. In addition, the CAP88-PC database, the user 
interface, input files, and output files, were modified to accommodate 
the FGR 13 data formats and nomenclature. Section 1.7 of the CAP88-PC 
Version 3 User's Guide (Docket EPA-HQ-OAR-2002-0050, Item 0047) 
describes the modifications incorporated into Version 3 relative to 
Version 2.1.

B. CAP88-PC Model Summary

    All versions of CAP-88 PC use a modified Gaussian plume equation to 
estimate the average dispersion of radionuclides released from up to 
six types of sources. The sources may be either elevated stacks, such 
as a smokestack, or uniform area sources, such as a pile of uranium 
mill tailings. Plume rise can be calculated assuming either a momentum 
or buoyant-driven plume. Assessments are made for a circular grid of 
distances and directions for a radius of up to 80 kilometers (50 miles) 
around the source. The Gaussian plume model produces results that agree 
with experimental data as well as any model, is fairly easy to work 
with, and is consistent with the random nature of turbulence. Site 
specific information on population locations and meteorological 
conditions are provided to CAP88-PC as input files developed by the 
user. The formats for these input files have not changed from the 
original mainframe version of the CAP88 code package.
    There are a few differences between CAP88-PC and earlier mainframe 
versions. When performing population dose assessments, CAP88-PC uses 
the distances in the population array to determine the sector midpoint 
distances where the code calculates concentrations. When an individual 
assessment is run, the sector midpoint distances are input by the user 
on the Run Option tab form. CAP88-PC only uses circular grids, whereas 
the mainframe version allowed users to define a square grid. Also, 
direct user input of radionuclide concentrations in each sector is not 
an option in CAP88-PC.
    CAP88-PC is also modified to do either ``Radon-only'' or ``Non-
Radon'' runs to conform to the format of the 1988 Clean Air Act NESHAPs 
Rulemaking. ``Radon-only'' assessments, which only have Rn-222 in the 
source term, automatically include working level calculations; any 
other source term ignores working levels. When performing ``Radon-
only'' runs, CAP88-PC has the capability to vary the equilibrium 
fractions for the Radon daughters based on the distance from the 
source; previously the equilibrium fractions were set to a constant of 
0.7. Synopsis reports customized to both ``Radon Only'' and ``Non-
Radon'' formats are automatically generated. Input of any additional 
radionuclides, even Rn-220, will cause CAP88-PC to omit working level 
calculations. Version 3 has not changed the ``Radon Only'' methodology 
relative to the previous Versions 2.0 and 2.1.
    The calculation of deposition velocity and the default scavenging 
coefficient in CAP88-PC is defined by current EPA policy. Deposition 
velocity is set to 3.5 x 10-\2\ (0.035) m/sec for Iodine, 
1.8 x 10-\3\ (0.0018) m/sec for particulate, and 0.0 m/sec 
for gas. The default scavenging coefficient is calculated as a function 
of annual precipitation, which is input on the Meteorological Data tab 
form. Version 3 has not modified these calculations.
    Organs and weighting factors have been modified in Version 3 to 
follow the FGR 13 method. In accordance with the FGR 13 dose model, the 
code now calculates dose for twenty-three (23) internal organs, rather 
than the seven (7) organs used in earlier versions. A twenty-fourth 
organ is also calculated, which is the total effective dose equivalent. 
The code now reports cancer risk for the fifteen (15) target cancer 
sites used in FGR 13. As was the case in Version 2, changing the organs 
and weights will invalidate the results.

C. Validation of the CAP88-PC Model

    The CAP88-PC programs represent one of the best available validated 
codes for the purpose of making comprehensive dose and risk 
assessments. The Gaussian plume model used in CAP88-PC to estimate 
dispersion of radionuclides in air is one of the most commonly used 
models in government guidebooks. It produces results that agree with 
experimental data as well as any model, is fairly easy to work with, 
and is consistent with the random nature of turbulence. Version 3 has 
not modified the basic Gaussian plume algorithm used by the AIRDOS 
module of CAP88-PC, and comparison of cases between Versions 2 and 3 
has shown no significant changes in the dispersion calculations.
    The Office of Radiation and Indoor Air has made comparisons between 
the predictions of annual average ground-level concentration to actual 
environmental measurements and found very good agreement. In the paper 
``Comparison of AIRDOS-EPA Prediction of Ground-Level Airborne 
Radionuclide Concentrations to Measured Values'' (Docket EPA-HQ-OAR-
2002-0050, Item 0048), environmental monitoring data at five DOE sites 
were compared to AIRDOS-EPA predictions. EPA concluded that the 
concentrations predicted by AIRDOS-EPA are in substantial agreement to 
the measured concentrations, within an acceptable uncertainty level.

D. Limitations of the CAP88-PC Model

    Like all models, there are some limitations in the CAP88-PC system. 
While up to six stack or area sources can be modeled, all the sources 
are modeled as if located at the same point; that is, stacks cannot be 
located in different areas of a facility. The same plume rise mechanism 
(buoyant or momentum) is used for each source. Also, area sources are 
treated as uniform. Variation in radionuclide concentrations due to 
complex terrain cannot be modeled. Errors arising from these 
assumptions will have a negligible effect for assessments where the 
distance to exposed individuals is large compared to the stack height, 
area or facility size.
    Dose and risk estimates from CAP88-PC are applicable only to low-
level chronic exposures, since the health effects and dosimetric data 
are based on low-level chronic intakes. CAP88-PC cannot be used for 
either short-term or high-level radionuclide intakes.
    These limitations, common to all versions of CAP88, have not 
changed in Version 3.

E. Summary of CAP88-PC Changes From Version 2.1 to Version 3

    Version 3 of CAP88-PC is a significant update to Version 2.1. The 
most significant change is the incorporation of the FGR 13 dose and 
risk factors. FGR 13 includes both dose and risk factors for 825 
isotopes rather

[[Page 8856]]

than the 265 previously available. The decay chains for these 825 
isotopes are now modeled using a full implementation of the Bateman 
decay equations to replace the predefined decay chains in previous 
versions. The FGR 13 dose and risk factors also introduce new 
functionality and terminology. Ingestion and inhalation factors are now 
a function of the chemical form of the isotope, which is entered by the 
user. The radionuclide inhalation absorption ``Class'' terminology has 
been replaced by the new ``Type'' nomenclature. The new types are F 
(fast), M (medium), and S (slow), analogous to the older classes D 
(day), W (week), and Y (year). FGR 13 assumes a 1.0 micron size for 
inhaled particles, so Version 3 sets all particle sizes to 1.0 micron. 
Gas and vapor forms use a particle size of 0.0. Although not 
implemented in Version 3, CAP88-PC now also contains additional 
functionality that may be added in later versions, including age 
dependent factors, factors for morbidity in addition to mortality, and 
factors for additional exposure pathways.
    To accommodate the FGR 13 methodology, CAP88-PC Version 3 also now 
calculates dose equivalent to 23 internal organs, and estimates the 
risk of cancer for 15 potential cancer induction sites. Additionally, 
CAP88-PC Version 3 no longer estimates genetic effects because genetic 
effects are not part of the FGR 13 dose and risk factor dataset.
    The pathway transfer factors for all elements in the CAP88-PC 
database have been updated in Version 3 to the values from the National 
Council on Radiation Protection and Measurement (NCRP) report number 
123, ``Screening Models for Releases of Radionuclides to Atmosphere, 
Surface Water, and Ground''. This was done to ensure that all the 
elements represented by the 825 isotopes in FGR 13 have appropriate 
elemental transfer factors.
    CAP88-PC Version 3 still reports data in the same report structure 
used by previous versions of CAP88-PC. This has been done to retain 
conformance of the model to the applicable regulation, 40 CFR part 61, 
subpart H. Accordingly, the dose factors used in Version 3 are the 
values in FGR 13 for adults, and the risk values reported by Version 3 
are those for mortality, not morbidity, although additional dose factor 
sets are now included in CAP88-PC Version 3. It is important to note 
that because of the extensive data modifications, Version 3 does not 
allow the use of case input files created under earlier versions to be 
used as input for Version 3. Previous POP and WIND files are still 
usable with Version 3.
    CAP88-PC Version 3 will generate dose and risk results that differ 
from those results calculated by previous versions. The primary reason 
for this difference is the change in dose and risk conversion factors. 
Revisions of CAP88-PC up to Version 3 used dose factors generated by 
the RADRISK code, which was based upon the uptake and dose models 
contained in ICRP Publications 26 and 30. Risk was calculated in the 
earlier versions from dose using a constant conversion factor of 0.0004 
risk per rem of whole body dose. Version 3 of CAP88-PC implements the 
dose conversion factors of FGR 13, which are calculated using models 
from more recent publications of the ICRP such as Publications 56, 66, 
67, 69, and 71, and calculates risk using risk factors that are 
specific to the isotope rather than using the conversion factor method 
of previous versions. The effective dose coefficient in FGR 13 is 
calculated using the tissue weighting factors of ICRP publication 60. 
Dose factors in CAP88-PC Version 3 are also now in many cases a 
function of the chemical form of the isotope. This functionality was 
not present in previous versions of CAP88-PC.
    Dose and risk results from CAP88-PC Version 3 also will differ from 
those calculated using previous versions because of a change in the 
elemental transfer factors. CAP88-PC Version 3 contains isotopes 
representing many more elements in the periodic table than were 
represented in previous versions of CAP88-PC. A new set of elemental 
transfer factors were required to support these new elements. CAP88-PC 
Version 3 replaces the transfer factors from the previous version of 
CAP88-PC with the factors listed in NCRP Publication 123.
    Dose and risk results calculated by CAP88-PC Version 3 may also 
differ from those calculated by previous versions because Version 3 
provides for a full incorporation of the decay chains for the 
radioisotopes represented in FGR-13. The new decay chain representation 
will most directly affect calculations that involve those radioisotopes 
that were not part of the decay chains represented in the earlier 
versions.
    The changes implemented in Version 3 of CAP88-PC improve the code 
by bringing both the software code base and the modeling data used by 
the code up to the latest standards. The updated code base makes CAP88-
PC Version 3 run faster and with greater stability on the latest 
Windows platforms, and provides improved debugging and troubleshooting 
tools. The updated code base also eases future coding modifications to 
make code support easier. By implementing the dose and risk factor data 
from FGR 13 and the elemental transport factors from NCRP 123, CAP88-PC 
Version 3 now incorporates the latest dose and risk modeling data 
recommended by EPA. The new data, combined with the improved methods 
for calculating decay chains, provides Version 3 of CAP88 with a much 
larger library of radioisotopes and a more current scientific 
methodology for calculating dose and risk.

    Dated: February 7, 2006.
Bonnie C. Gitlin,
Acting Director, Radiation Protection Division, Office of Radiation and 
Indoor Air.
 [FR Doc. E6-2405 Filed 2-17-06; 8:45 am]
BILLING CODE 6560-50-P