METHOD
115-MONITORING FOR RADON-222 EMISSIONS
This appendix
describes the monitoring methods which must be used in determining the
radon-222 emissions from underground uranium mines, uranium mill tailings
piles, phosphogypsum stacks, and other piles of waste material emitting radon.
1. Radon-222
Emissions from Underground Uranium Mine Vents.
1.1 Sampling Frequency
and Calculation of Emissions.
1.2 Test Methods and
Procedures
2. Radon-222 Emissions
from Uranium Mill Tailings Piles.
2.1 Measurement and
Calculation of Radon Flux from Uranium Mill Tailings Piles.
2.1.1 Frequency of Flux
Measurement.
2.1.2 Distribution of Flux
Measurements.
2.1.3 Number of Flux
Measurements.
2.1.4 Restrictions to
Radon Flux Measurements.
3.0 Radon-222 Emissions
from Phosphogypsum Stacks.
3.1 Measurement and
Calculation of the Mean Radon Flux.
3.1.1 Frequency of
Measurements.
3.1.2 Distribution and
Number of Flux Measurements.
3.1.3 Number of Flux
Measurements.
3.1.4 Restrictions to
Radon Flux Measurements.
3.1.6 Radon Flux
Measurements.
4.0 Quality Assurance
Procedures for Measuring Rn-222 Flux.
C. Calibration
Procedures and Frequency
D. Internal Quality
Control Checks and Frequency
E. Data Precision,
Accuracy, and Completeness
1. Radon-222 Emissions from Underground Uranium Mine Vents.
1.1 Sampling Frequency and Calculation of Emissions.
Radon-222
emissions from underground uranium mine vents shall be determined using one of the
following methods:
1.1.1 Continuous Measurement.
These
measurements shall be made and the emissions calculated as follows:
(a) The
radon-222 concentration shall be continuously measured at each mine vent whenever
the mine ventilation system is operational.
(b) Each mine
vent exhaust flow rate shall be measured at least 4 times per year.
(c) A weekly
radon-222 emission rate for the mine shall be calculated and recorded weekly as
follows:
where:
(d) The annual radon-222 emission rate
is the sum of the weekly emission rates during a calendar year.
1.1.2 Periodic Measurement.
This method is
applicable only to mines that continuously operate their ventilation system
except for extended shutdowns. Mines which start up and shut down their
ventilation system frequently must use the continuous measurement method
describe in Section 1.1.1 above. Emission rates determined using periodic
measurements shall be measured and calculated as follows:
(a) The radon-222
shall be continuously measured at each mine vent for at least one week every
three months.
(b) Each mine
vent exhaust flow rate shall be measured at least once during each of the
radon-222 measurement periods.
(c) A weekly
radon-222 emission rate shall be calculated for each weekly period according to
the method described in Section 1.1.1. In this calculation T=168 hr.
(d) The annual
radon-222 emission rate from the mine should be
calculated as
follows:
where:
1.2 Test Methods and Procedures
Each
underground mine required to test its emissions, unless an equivalent or
alternative method has been approved by the Administrator, shall use the
following test methods:
1.2.1 Test
Method 1 of appendix A to part 60 shall be used to determine velocity
traverses. The sampling point in the duct shall be either the centroid of the
cross section or the point of average velocity.
1.2.2 Test
Method 2 of appendix A to part 60 shall be used to determine velocity and
volumetric flow rates.
1.2.3 Test
Methods A-6 or A-7 of appendix B, Method 114
to part 61 shall be used for the analysis of radon-222. Use of Method A - 7
requires prior approval of EPA based on conditions described in appendix B.
1.2.4 A
quality assurance program shall be conducted in conformance with the programs
described for Continuous Radon Monitors and Alpha Track Detectors in EPA
520/1-89-009. (2)
2. Radon-222 Emissions from Uranium Mill Tailings Piles.
2.1 Measurement and Calculation of Radon Flux from Uranium Mill Tailings
Piles.
2.1.1 Frequency of Flux Measurement.
A single set
of radon flux measurements may be made, or if the owner or operator chooses,
more frequent measurements may be made over a one year period. These
measurements may involve quarterly, monthly or weekly intervals. All radon
measurements shall be made as described in paragraphs 2.1.2 through 2.1.6
except that for measurements made over a one year period, the requirement of
paragraph 2.1.4(c) shall not apply. The mean radon flux from the pile shall be
the arithmetic mean of the mean radon flux for each measurement period. The
weather conditions, moisture content of the tailings and area of the pile
covered by water existing at the time of the measurement shall be chosen so as
to provide measurements representative of the long term radon flux from the
pile and shall be subject to EPA review and approval.
2.1.2 Distribution of Flux Measurements.
The
distribution and number of radon flux measurements required on a pile will
depend on clearly defined areas of the pile (called regions) that can have
significantly different radon fluxes due to surface conditions. The mean radon
flux shall be determined for each individual region of the pile. Regions that shall
be considered for operating mill tailings piles are:
(a) Water
covered areas,
(b) Water
saturated areas (beaches),
(c) Dry top
surface areas, and
(d) Sides,
except where earthen material is used in dam construction.
For mill
tailings after disposal the pile shall be considered to consist of only one
region.
2.1.3 Number of Flux Measurements.
Radon flux
measurements shall be made within each region on the pile, except for those
areas covered with water. Measurements shall be made at regularly spaced
locations across the surface of the region, realizing that surface roughness
will prohibit measurements in some areas of a region. The minimum number of
flux measurements considered necessary to determine a representative mean radon
flux value for each type of region on an operating pile is:
(a) Water
covered area-no measurements required as radon flux is assumed to be zero,
(b) Water
saturated beaches-100 radon flux measurements,
(c) Loose and
dry top surface-100 radon flux measurements,
(d) Sides-100
radon flux measurements, except where earthern material is used in dam
construction.
For a mill
tailings pile after disposal which consists of only one region a minimum of 100
measurements are required.
2.1.4 Restrictions to Radon Flux Measurements.
The following
restrictions are placed on making radon flux measurements:
(a)
Measurements shall not be initiated within 24 hours of a rainfall.
(b) If a
rainfall occurs during the 24 hour measurements period, the measurement is
invalid if the seal around the lip of the collector has washed away or if the
collector is surrounded by water.
(c)
Measurements shall not be performed if the ambient temperature is below 35¡F or
if the ground is frozen.
2.1.5 Areas of Pile Regions.
The approximate
area of each region of the pile shall be determined in units of square meters.
2.1.6 Radon Flux Measurement.
Measuring
radon flux involves the adsorption of radon on activated charcoal in a
large-area collector. The radon collector is placed on the surface of the pile
area to be measured and allowed to collect radon for a time period of 24 hours.
The radon collected on the charcoal is measured by gamma-ray spectroscopy. The
detailed measurement procedure provided in appendix A of EPA 520/5-85-0029(1) shall
be used to measure the radon flux on uranium mill tailings, except the surface
of the tailings shall not be penetrated by the lip of the radon collector as
directed in the procedure, rather the collector shall be carefully positioned
on a flat surface with soil or tailings used to seal the edge.
2.1.7 Calculations.
The mean radon
flux for each region of the pile and for the total pile shall be calculated and
reported as follows:
(a) The
individual radon flux calculations shall be made as provided in appendix A EPA
86 (1). The mean radon flux for each region of the pile shall be calculated by
summing all individual flux measurements for the region and dividing by the
total number of flux measurements for the region.
(b) The mean
radon flux for the total uranium mill tailings pile shall be calculated as
follows.
where:
2.1.8 Reporting.
The results of
individual flux measurements, the approximate locations on the pile, and the
mean radon flux for each region and the mean radon flux for the total stack
shall be included in the emission test report. Any condition or unusual event
that occurred during the measurements that could significantly affect the
results should be reported.
3.0 Radon-222 Emissions from Phosphogypsum Stacks.
3.1 Measurement and Calculation of the Mean Radon Flux.
Radon flux
measurements shall be made on phosphogypsum stacks as described below:
3.1.1 Frequency of Measurements.
A single set
of radon flux measurements may be made after the phosphogypsum stack becomes
inactive, or if the owner or operator chooses, more frequent measurements may
be made over a one year period. These measurements may involve quarterly,
monthly or weekly intervals. All radon measurements shall be made as described
in paragraphs 3.1.2 through 3.1.6 except that for measurements made over a one
year period, the requirement of paragraph 3.1.4(c) shall not apply. For
measurements made over a one year period, the radon flux shall be the
arithmetic mean of the mean radon flux for each measurement period.
3.1.2 Distribution and Number of Flux Measurements.
The
distribution and number of radon flux measurements required on a stack will
depend on clearly defined areas of the stack (called regions) that can have significantly
different radon fluxes due to surface conditions. The mean radon flux shall be
determined for each individual region of the stack. Regions that shall be
considered are:
(a) Water
covered areas,
(b) Water
saturated areas (beaches),
(c) Loose and
dry top surface areas,
(d)
Hard-packed roadways, and
(e) Sides.
3.1.3 Number of Flux Measurements.
Radon flux
measurements shall be made within each region on the phosphogypsum stack,
except for those areas covered with water. Measurements shall be made at
regularly spaced locations across the surface of the region, realizing that
surface roughness will prohibit measurements in some areas of a region. The
minimum number of flux measurements considered necessary to determine a
representative mean radon flux value for each type of region is:
(a) Water
covered area-no measurements required as radon flux is assumed to be zero,
(b) Water
saturated beaches-50 radon flux measurements,
(c) Loose and
dry top surface-100 radon flux measurements,
(d)
Hard-packed roadways-50 radon flux measurements, and
(e) Sides-100
radon flux measurements.
A minimum of
300 measurements are required. A stack that has no water cover can be
considered to consist of two regions, top and sides, and will require a minimum
of only 200 measurements.
3.1.4 Restrictions to Radon Flux Measurements.
The following
restrictions are placed on making radon flux measurements:
(a)
Measurements shall not be initiated within 24 hours of a rainfall.
(b) If a
rainfall occurs during the 24 hour measurement period, the measurement is
invalid if the seal around the lip of the collector has washed away or if the
collector is surrounded by water.
(c)
Measurements shall not be performed if the ambient temperature is below 35 ¡F
or if the ground is frozen.
3.1.5 Areas of Stack Regions.
The
approximate area of each region of the stack shall be determined in units of
square meters.
3.1.6 Radon Flux Measurements.
Measuring
radon flux involves the adsorption of radon on activated charcoal in a
large-area collector. The radon collector is placed on the surface of the stack
area to be measured and allowed to collect radon for a time period of 24 hours.
The radon collected on the charcoal is measured by gamma-ray spectroscopy. The detailed
measurement procedure provided in appendix A of EPA 520/5-85-0029(1) shall be
used to measure the radon flux on phosphogypsum stacks, except the surface of
the phosphogypsum shall not be penetrated by the lip of the radon collector as
directed in the procedure, rather the collector shall be carefully positioned
on a flat surface with soil or phosphogypsum used to seal the edge.
3.1.7 Calculations.
The mean radon
flux for each region of the phosphogypsum stack and for the total stack shall
be calculated and reported as follows:
(a) The individual radon flux
calculations shall be made as provided in appendix A EPA 86 (1). The mean radon
flux for each region of the stack shall be calculated by summing all individual
flux measurements for the region and dividing by the total number of flux
measurements for the region.
(b) The mean
radon flux for the total phosphogypsum stack shall be calculated as follows.
where:
3.1.8 Reporting.
The results of
individual flux measurements, the approximate locations on the stack, and the
mean radon flux for each region and the mean radon flux for the total stack
shall be included in the emission test report. Any condition or unusual event
that occurred during the measurements that could significantly affect the results
should be reported.
4.0 Quality Assurance Procedures for Measuring Rn-222 Flux.
A. Sampling Procedures
Records of
field activities and laboratory measurements shall be maintained. The following
information shall be recorded for each charcoal canister measurement:
(a) Site
(b) Name of
pile
(c) Sample
location
(d) Sample ID
number
(e) Date and
time on
(f) Date and
time off
(g)
Observations of meteorological conditions and comments
Records shall
include all applicable information associated with determining the sample
measurement, calculations, observations, and comments.
B. Sample Custody
Custodial
control of all charcoal samples exposed in the field shall be maintained in
accordance with EPA chain-of-custody field procedures. A control record shall
document all custody changes that occur between the field and laboratory
personnel.
C. Calibration Procedures and Frequency
The
radioactivity of two standard charcoal sources, each containing a carefully
determined quantity of radium-226 uniformly distributed through 180g of
activated charcoal, shall be measured. An efficiency factor is computed by
dividing the average measured radioactivity of the two standard charcoal
sources, minus the background, in cpm by the known radioactivity of the
charcoal sources in dpm. The same two standard charcoal sources shall be
counted at the beginning and at the end of each day's counting as a check of
the radioactivity counting equipment. A background count using unexposed
charcoal should also be made at the beginning and at the end of each counting
day to check for inadvertent contamination of the detector or other changes
affecting the background. The unexposed charcoal comprising the blank is
changed with each new batch of charcoal used.
D. Internal Quality Control Checks and Frequency
The charcoal
from every tenth exposed canister shall be recounted. Five percent of the
samples analyzed shall be either blanks (charcoal having no radioactivity
added) or samples spiked with known quantities of radium-226.
E. Data Precision, Accuracy, and Completeness
The precision,
accuracy, and completeness of measurements and analyses shall be within the
following limits for samples measuring greater than 1.0 pCi/m2 -s.
(a) Precision:
10%
(b) Accuracy:
±10%
(c)
Completeness: at least 85% of the measurements must yield useable results.
5.0 References.
(1) Hartley,
J.N. and Freeman, H.D., "Radon Flux Measurements on Gardinier and Royster
Phosphogypsum Piles Near Tampa and Mulberry, Florida," U.S. Environmental
Protection Agency Report, EPA 520/5-85-029, January 1986.
(2)
Environmental Protection Agency, "Indoor Radon and Radon Decay Product
Measurement Protocols", EPA 520/1-89-009, U.S. Environmental Protection
Agency, Washington, DC. (1989). [38 FR 8826, Apr. 6, 1973]