[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]
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