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Chapter 3 is about Radiological air sampling and its an important technique that is used to monitor and assess whether the presence of radioactive particles or gasses are in the air. This process is essential for ensuring the safety of the public, workers, and the environment in areas' that radioactive materials are handled, such as research facilities, medical institutions, or nuclear power plants. Click here to go to the next lesson.
Purpose:
Radiation Protection: To ensure that radiation levels in the air are within acceptable limits and do not pose a risk to human health.
Environmental Monitoring: To assess the impact of radioactive releases on the surrounding environment.
Nuclear Facility Safety: To monitor potential leaks or releases of radioactive materials within nuclear facilities.
Types of Sampling:
Particulate Sampling: Involves capturing solid radioactive particles (e.g., dust, aerosols) suspended in the air. This is often done using air filters or impactors.
Gaseous Sampling: Involves collecting radioactive gases (e.g., noble gases, iodine) from the air using specialized absorbent materials or gas sampling systems.
Sampling Equipment:
Air Samplers: These devices are designed to draw air through sampling media, where radioactive particles or gases are captured.
Filters: High-efficiency particulate air (HEPA) filters are commonly used to collect airborne radioactive particles.
Sorbent Beds: Used to capture radioactive gases. These beds are filled with materials that can adsorb specific radioactive gases.
Sampling Locations:
Sampling locations are strategically chosen to capture air samples from areas of interest, such as near potential sources of radiation or in areas where workers are present.
Sampling Frequency:
The frequency of air sampling depends on the specific requirements of the facility, regulations, and the potential for radioactive releases. Regular and continuous monitoring is often performed, especially in nuclear power plants.
Analysis:
After collecting air samples, they are sent to a laboratory for analysis. Various techniques, including gamma spectroscopy, liquid scintillation counting, and gas chromatography, can be used to determine the type and quantity of radioactive materials present.
Reporting and Regulatory Compliance:
Results from radiological air sampling are reported to relevant regulatory authorities to ensure compliance with safety standards and regulations.
Emergency Response:
Radiological air sampling is an essential component of emergency response plans in case of accidents or incidents involving the release of radioactive materials. Rapid assessment of airborne contamination helps in making informed decisions about evacuations and protective measures.
Calibration and Quality Assurance:
To ensure the accuracy and reliability of air sampling results, calibration and quality assurance programs are implemented, including regular equipment maintenance and performance checks.
Radiological air sampling plays a critical role in safeguarding against the harmful effects of radiation exposure and maintaining the safety of nuclear facilities and the surrounding environment. It helps ensure that radiation levels are well-monitored and controlled to prevent health risks.
This procedure describes when air samples must be
collected and the processes for sample collection, determining airborne
concentrations, and taking appropriate actions based on analytical
results. Sampling methods are described
for airborne particulates, iodine and noble gas.
This procedure
describes processes that supplemental RP personnel perform to assess
radiological hazards from airborne radioactivity. Generic instructions are provided to enable
supplemental personnel to sample and assess airborne hazards with air samplers
and counting instruments typically used in the industry. Site-specific training is required if
supplemental personnel are expected to perform gamma spectroscopy analysis or
use programmed instruments that simultaneously count both alpha and beta
radiation.
Instructions are
provided to analyze particulate air samples to determine the following:
·
A DAC fraction from beta-gamma emitters using a
counting system and assuming the total activity is Co-60, or other nuclide(s)
as directed by site procedures.
·
A βγ/α Ratio when required by this
procedure.
·
An estimate of the total DAC fraction, including
transuranics, assuming all alpha emitting activity measured with a counting
system is Am-241, or other nuclide(s) as directed by site procedures.
·
An estimate of the total DAC fraction, including
transuranics, if required by the site in lieu of completing an alpha
analysis. If such estimates are
required, the site is responsible for specifying a TRU multiplier based on site
characterization and/or conservative assumptions. This procedure does not provide instructions
for site characterization.
This procedure does not provide instructions
for sampling tritium, analyzing iodine sample cartridges, or analyzing noble
gas samples since these are tasks that are rarely performed by supplemental
personnel. Site specific training and
qualification should be performed if supplemental personnel are expected to
sample for tritium or analyze iodine sample cartridges or noble gas samples.
The forms referenced by
this procedure are examples used to describe the pertinent information that
should be recorded for future reference.
Plant procedures may specify the use of equivalent forms or the use of
electronic media for the same purposes.
Calculations described
in this procedure are provided to define how sample parameters are used to
evaluate the magnitude and significance of airborne radioactivity. Site procedures may use alternative
equations, provide graphs to substitute for calculations, direct the use of
software for the same purposes, and/or authorize only site personnel to perform
calculations.
Member utilities are
expected to use this standard to enable supplemental workers to transition
between nuclear power plants with minimal site-specific training. Compliance with these instructions is
expected without additional site requirements or process deviations being
imposed that may require additional training or challenge the performance of
supplemental workers.
This procedure is used
to train and instruct supplemental radiological protection technicians. Member utilities will implement these process
requirements in site procedures and update site procedures whenever
requirements or process steps in this Nuclear Industry Standard Process (NISP)
are revised. Current revisions are
maintained on the INPO website.
Terms and definitions
not defined in this procedure are provided in NISP-RP-13, Radiological Protection Glossary.
Clarifying notes for requirements and
process steps are provided in Section 4.0 using superscript numbers in sections
2.0 and 3.0.
2.1
Evaluation of air sample results requires
comparison of airborne concentrations to the Derived Air Concentration (DAC)
values in 10 CFR 20, Appendix B. The
following terminology is used in describing the overall process in this
procedure.
2.1.1
βγ/α Ratio – The total activity of
beta-gamma emitters divided by the total activity of transuranic alpha emitters
as measured by counting systems. An
increasing presence of transuranics is indicated by a decreasing ratio. The term is called an Activity Ratio or the
Beta-Gamma to Alpha Ratio.
2.1.2
fDACβγ – The sum of
each beta-gamma emitting nuclide’s activity divided by its corresponding DAC
value; the term is called the Beta-Gamma DAC Fraction. In some cases, the total beta-gamma activity
may be divided by the most restrictive nuclide (e.g. Co-60 or Cs-137) for an
approximation of the Beta-Gamma DAC Fraction.
2.1.3
fDACα
– The sum of each alpha emitting nuclide’s activity divided by its
corresponding DAC value; the term is called the Alpha DAC Fraction. In some cases, the total alpha activity may
be divided by the most restrictive nuclide DAC value (e.g. Am-241) for an
approximation of the Alpha DAC Fraction.
2.1.4
fDACTotal – The sum
of fDACβγ and fDACα; the term is
called the Total DAC Fraction.
2.1.5
DACFractionRatio
– The ratio of fDACα/ fDACβγ; the term is called the DAC Fraction Ratio. This ratio shows the relative significance of
transuranics in contributing to potential internal dose to workers. This value can be determined using
conservative assumptions for the nuclides present or use nuclide abundances
from site characterization as described in Reference 5.1.
2.1.6
TRU Multiplier – A value equal to 1 + DACFractionRatio that can be
multiplied by the fDACβγ to estimate the fDACTotal
in lieu of completing an alpha analysis.
A graph showing TRU Multiplier values based on βγ/α Ratios,
assuming Co-60 and Am-241, is provided in Attachment 3.
2.2
Air samples are classified based on the location
and purpose for collecting the sample as follows:
2.2.1
Breathing Zone Air Sample – An air sample where
the filter media is within approximately 12 inches of a worker’s head1.
a. A
personal air sampler is set up with the filter media within a 25 cm (10 inches)
radius of the worker’s nose and mouth (Reference 5.1).
b. A
lapel air sampler should be used if the results will be used to assign dose to
a worker.
2.2.2
Work Area Air Sample – An air sample where the
filter media is located to provide an average measurement of airborne radioactivity
to which workers are exposed in a work area.
a. Either
grab samples or continuous sampling may be used provided sample volumes are
controlled to obtain an MDA less than 0.3 DAC for the nuclides being sampled.
b. Place
sampling media as close to the breathing zone as practicable without
interfering with the work or the worker.
c. Place
the sampling media downstream of the airborne source if airflow patterns may
affect dispersion.
2.2.3
General Area Air Sample – An air sample located
to accomplish one or more of the following:
a. Determine
potential airborne hazards.
b. Verify
postings and boundaries.
c. Determine
the effectiveness of engineering controls.
d. Measure
general or average concentrations.
e. Detect
unexpected releases into a workplace.
2.3
Plant RP organizations are responsible for
categorizing plant systems and areas based on the potential contribution of
transuranics to the internal dose of workers.
Categories are defined as follows:
2.3.1
Alpha Level 1 Area – The internal dose from
alpha emitting transuranics is not likely to exceed 10% of the total internal
dose from inhalation. Alpha Level 1
Areas have a βγ/α Ratio greater than 30,000 or
alpha activity levels are less than 20 dpm/100 cm2. An area not posted as an Alpha Level 2 or 3
Area is an Alpha Level 1 Area. Postings
are not required for an Alpha Level 1 Area.
2.3.2
Alpha Level 2 Area – Alpha emitting transuranics
are likely to contribute between 10% and 90% of the total internal dose from
inhalation. Alpha Level 2 Areas have a βγ/α Ratio between 300 and 30,000.
Alpha Level 2 Areas are posted per NISP-RP-04, Posting and Labeling of Radiological Areas.
2.3.3
Alpha Level 3 Area – The internal dose from
alpha emitting transuranics is likely to exceed 90% of the total internal dose
from inhalation. Alpha Level 3 Areas
have a βγ/α Ratio less than 300. Alpha
Level 3 Areas are posted per NISP-RP-04.
2.4
Analyze a particulate air sample for alpha
emitting transuranics using the following criteria:
2.4.1
An air sample measures a fDACβγ ≥ 1.0 DAC.
2.4.2
As required by the option used by the site as described
in Attachment 4 for Alpha Level 2 Areas.
2.4.3
An air sample was collected in an Alpha Level 3
Area.
2.5
Prejob planning should ensure personnel
collecting air samples understand the following:
2.5.1
When samples are needed based on the conditions
listed in section 3.1 of this procedure.
2.5.2
Required breathing zone, work area, and general
area air samples.
2.5.3
Minimum sample volumes required by site
procedures. Typical requirements for
sample volume are provided below:
a. Sample
250 liters (8.8 ft3) for corrosion and fission products.
1) A
250 liter sample can collect a sufficient amount of Co-60 to measure 0.3 DAC if
the counting system has an MDA less than 1,600 dpm of Co-60.
b. Sample
1,000 liters (35.3 ft3) for transuranics.
1) A
1,000 liter sample can collect a sufficient amount of Am-241 to measure 0.3 DAC
if the counting system has an MDA of 2.8 dpm and there is negligible
self-absorption within the sample filter.2
2.6
Air samples should be collected to evaluate the
airborne hazards due to the specific work activities performed.
2.6.1
Collect grab samples during expected periods of
actual or potentially highest airborne concentrations and evaluate them as
quickly as practicable to determine the need for adjusting engineering
controls, respirators, area evacuation, area posting, or worker relief from
unnecessary respirator use.
2.6.2
For work that has the potential to generate
airborne radioactivity for a longer period of time, e.g. over an hour, operate
an air sampler continuously while work is in progress.
a. Change
out filters with the objective to evaluate sample results from specific
activities more likely to generate airborne radioactivity, e.g. a system
breach, lapping of a valve seat, decontamination, etc.
2.7
Review and comply with site procedures for the
issue and return of air sampling equipment and portable instruments.
2.8
Always inspect air sampling equipment and sample
media prior to use to ensure the following, as applicable:
2.8.1
Physical damage does not exist that could affect
operation.
2.8.2
Sample pumps have been calibrated within the
required time frame.
2.8.3
Any batteries that are required are charged for
operation.
2.8.4
Any AC power cords are not damaged and AC power
is available where the sample will be taken.
2.8.5
Operability is checked by starting the sampler
and observing expected parameters.
2.8.6
Sample holders or Marinelli beakers are not
damaged.
2.8.7
Sample holders do not have any cracked or
missing O-rings or screens.
2.8.8
Threads and connectors are not damaged and
function as expected.
2.8.9
The age of filter media has not exceeded a
required shelf-life, e.g. iodine cartridges.
2.9
Avoid placing sampler motors directly on
contaminated surfaces (e.g. greater than 10,000 dpm/100 cm2) where
the motor exhaust could create airborne radioactivity.
2.9.1
Consider covering the surface or suspending the
sampler motor to minimize the potential for airborne.
2.10 Do
not use electrical devices in atmospheres that may be approaching the Lower
Explosive Limit, e.g. 2% to 4% H2.
2.11 Exercise
care to prevent cross contamination of sample filters during the removal and
bagging process.
2.12 If
air sample results indicate airborne concentrations exceeded 0.3 DAC, or a
personal air sampler indicates an intake could occur greater than 4 DAC-hours,
in an area that is not posted and controlled as an Airborne Radioactivity Area,
take the following actions:
2.12.1 If
radon interference is suspected during field analysis, consult RP supervision
to determine if follow-up actions should be delayed until a
radon-discriminating analysis is completed.
2.12.2 Stop
work, evacuate workers from the affected area, and collect grab samples to determine
if airborne concentrations are sustained and to identify the source if unknown.
2.12.3 Inform
workers in the area without respiratory protection that airborne radioactivity
was measured and potential exposures will be evaluated.
2.12.4 If
the conditions causing the airborne radioactivity may still exist or are
unknown, immediately post and control the area as an Airborne Radioactivity
Area.
2.12.5 Notify
RP supervision and ensure the occurrence is documented in the plant corrective
action program to identify the cause of the conditions and any corrective
actions, including an assessment of potential doses to workers.
3.0
Process Instructions
The
basic process for air sampling is to obtain a sample, analyze the sample, and
then take the appropriate actions if airborne concentrations exceed 0.3
DAC. Appropriate actions include
ensuring the area is posted as an Airborne Radioactivity Area per NISP-RP-04, Radiological Posting and Labeling and to
determine cause and corrective actions if the airborne radioactivity was not anticipated. The analysis portion of this process for a
particulate filter has additional steps to determine the abundance of alpha
emitting transuranic nuclides in the airborne mixture. The process diagram below provides the
standard process for analysis of a particulate air sample filter. Attachments 1 and 2 provide more detailed
instructions to complete this process.
3.1
Determine the Need for an Air Sample
3.1.1 Comply
with the air sampling requirements as stated in plant procedures, RWPs, ALARA
Plans or as directed by RP supervision.
a. Notify
RP supervision if an activity may warrant air sampling but the need for an air
sample has not been identified.
3.1.2 Collect
work area air samples whenever respiratory protective equipment is worn to
validate that the protection factor was sufficient to limit the intake of
radioactive material.
3.1.3 Use
the following guidelines to identify the need for an air sample.
a. During
any work or operation that is known to have a potential for causing airborne
radioactivity such as:
1) Grinding,
welding, burning, cutting, hydrolasing, vacuuming, sweeping, or using
compressed air on contaminated equipment.
2) Using
volatile substances on contaminated surfaces.
3) When
compacting waste.
4) When
removing contaminated insulation.
b. During
any work or operation that involves the breach of a radioactive system for
which the potential for measurable airborne radioactivity is known to exist.
c. Prior
to or during initial entry into a known or suspected airborne radioactivity
area such as:
1) Steam
leaks from a primary system.
2) Steam
leaks from a BWR secondary system.
3) Leaks
from a BWR off-gas systems
4) Leaks
from a gaseous waste processing system.
d. When
working in an area with levels of dry removable contamination that could become
suspended in concentrations greater than 0.3 DAC such as:
1) Greater
than 100,000 dpm/100 cm2 of βγ
emitting nuclides.
2) When
aggressive work (e.g. cutting, grinding, welding, etc.) is performed in Alpha
Level 2 Areas or on systems with suspected but unknown amounts of
transuranics.
3) Work
in Alpha Level 3 Areas.
e. Initial
entry into a PWR containment or BWR drywell during power operation with
subsequent air samples as directed by RP supervision.
f.
Initial entry into a PWR containment or BWR
drywell following shutdown as directed by RP supervision.
g. Prior
to or during initial entry into any high-risk area such as steam generators,
reactor cavities, reactor vessels, or radioactive waste tanks, and periodically
thereafter.
h. When
environmental factors such as heat, air flows, low humidity, etc. increase the
potential for highly contaminated surfaces, components, and filters to dry and
the contamination to become suspended in air.
i.
A significant spill or spread of contamination
has occurred.
j.
System leakage or work activities can result in
airborne radioactivity and an area sample is needed to provide a timely alert
of the changing condition.
k. When
DAC-Hour tracking is used to monitor worker intakes.
l.
When fuel leaks have occurred elevating noble
gas, iodine, and transuranic nuclides in the RCS. Plant-specific procedures are used in
response to fuel failure to monitor potential doses to workers.
m. A
potential airborne pathway exists for a release to the environment. Consult with personnel responsible for
effluent monitoring to ensure appropriate locations and parameters are
established for airborne monitoring.
3.2
Collect a Particulate and Iodine Air Sample
WARNING
Do not use electrical
devices in atmospheres that may be approaching the Lower Explosive Limit, e.g.
2% to 4% H2.
3.2.4 Use
an iodine sampling cartridge as required by site RP supervision, RWPs and/or
ALARA Plans.
a. Site
RP management may discontinue sampling for iodine when sample trends show that
iodine is not a concern.
b. Use
silver zeolite cartridges in noble gas atmospheres when directed by RP
supervision.
1) Ensure,
through prejob planning, that hydrogen is not present when using a silver
zeolite cartridge per Reference 5.2.
3.2.5 Select
an appropriate sampling method considering the following:
a. Use
a grab sampler to obtain an air sample in a short period of time.
1) Grab
samples are used to quickly verify airborne concentrations during a system
breach, monitor work area concentrations for short duration work, or in
conjunction with low volume air samplers to determine peak airborne
concentrations.
b. Use
a continuous air sampler to collect samples over a longer period of time such
as the entire duration of the work or continuously for routine verification
that airborne radioactivity is not present.
c. Use
a sample head connected to a remote pump with tubing when conditions limit
placing the air pump at the sampling location.
1) Refer
to site procedures to determine the allowable length of tubing.
2) Avoid
the use of tubing prior to the inlet of the sample head due to potential plate
out of radioactive material in the tubing prior to the air entering the filter
media.
3.2.6 Obtain
the appropriate air sampling pump for the type of sampling required.
3.2.7 Follow
the guidelines in Attachment 5 to set up and operate the sampler.
3.2.8 Inspect
the equipment to ensure it is operable and reliable.
3.2.9 Load
the particulate filter and iodine cartridge7 in the sample holder.
a. Ensure
filters are aligned or marked as needed to indicate the collection side that
should face the detector during analysis.
3.2.10 Position
the air sample filters as needed for a breathing zone, work area, or general
area sample and commence operation of the sampler to coincide with the activities
expected to generate airborne radioactivity.
a. Collect
a minimum volume as specified in section 2.5.3 of this procedure unless
otherwise specified by work instructions, the RWP, ALARA Plan, or RP
supervision.
3.2.11 Exercise
care to prevent cross contamination of the filters during the removal and
bagging process.
3.2.12 Complete
Attachment 1 (or site equivalent form) to record important sample parameters
for required analyses.
3.2.13 If
the sample was obtained in a noble gas atmosphere, consider purging the gas
from the sample media by running the sampler 1 to 2 minutes in an area where
noble gas, airborne particulates, or iodine are not present.
3.3
Collect a Noble Gas Sample
3.3.14 Open
the lid of a Marinelli and wave the Marinelli in the atmosphere for 15 to 30
seconds to allow the Marinelli contents to equilibrate with the atmosphere.
a. Place
and seal the lid on the Marinelli prior to leaving the sampling area.
3.3.15 Use
water displacement to collect noble gas.
a. Obtain
a 1 liter or 4 liter Marinelli beaker approved for gamma spectroscopy that has
a removable lid.
b. Fill
the container completely with demineralized water and seal the container.
c. Proceed
to the area where the sample is to be collected, open the container, pour the
water into a floor drain or another container, and re-seal the sample
container.
d. Complete
Attachment 1 (or site equivalent form) to record important sample parameters
for required analyses.
3.3.16 Use
a sample pump to collect noble gas per site procedures. Generic steps are listed below.
a. Obtain
a 1 liter or 4 liter Marinelli beaker that has stopcocks and is approved for
gamma spectroscopy.
b. Obtain
a low flow air pump (e.g. 15
lpm).
c. Perform
an inspection to ensure the equipment is operable.
d. Connect
the sample pump to the sample container with vacuum tubing.
e. Open
the valves on the container and start the sample pump.
f.
Allow a sufficient purge time to totally
displace the container volume with the sampled atmosphere (e.g., for a 4 liter
container, a volume of at least 20 liters is needed).
g. Stop
the pump and close the inlet and outlet valves.
h. Complete
Attachment 1 (or site equivalent form) to record important sample parameters
for required analyses.
i.
Submit the sample for gamma spectroscopy
analysis.
3.4
Operate a Continuous Air Monitor (CAM)
3.4.17 When
assigned responsibility to monitor or maintain a CAM, ensure prejob planning
activities provide instructions for the following:
a. Identification
of status lights that indicate normal operation.
b. Identification
of status lights and any alarms that indicate increased airborne
concentrations.
c. The
proper sequence for manipulating the CAM to change out filters.
3.4.18 Take
the following actions if an unexpected alarm occurs from a continuous air
monitor.
a. If
a work activity is causing increased airborne radioactivity in the area, stop
work and evacuate workers from the immediate area.
b. Collect
grab air samples for confirmation of airborne concentrations.
c. If
it is unlikely that a work activity is causing increased airborne
radioactivity, survey the area to determine if an increase in background
radiation levels caused the alarm.
d. Notify
RP supervision of the alarm and known conditions for further direction.
3.5
Set Up and Operate a Personal Air Sampler
3.5.19 Issue
personal air samplers as required by the RWP.
3.5.20 Issue
personal air samplers to each worker in an Alpha Level 2 or 3 Area based on the
following criteria:
a. Work
in Alpha Level 3 Areas.
b. Aggressive
work in Alpha Level 2 Areas or on systems with suspected but unknown amounts of
transuranics.
1) Examples
of aggressive work include cutting, grinding, welding, etc.
c. Exceptions
may be made for the following:
1) When
air supplied suits are worn if the industrial hazards associated with the use
of a personal air sampler outweigh the benefits.
2) Where
a periodic (non-incident based) alpha excreta sampling program is in place.
3) During
a specific task evolution where it is concluded that a personal air sampler is
not necessary, because the potential for airborne alpha had been evaluated and
is considered improbable, and appropriate stop work controls are in place and
communicated to the workers.
4) Where
engineering controls, (e.g. a glove box) adequately contain the source term.
3.5.21 Ensure
work area sampling is also performed where personal air samplers are in use to
provide a complete assessment of the airborne hazard.
a. Measurements
from a personal air sampler are not reliable for a complete hazard assessment,
including posting criteria, due to:
1) Difficulties
in controlling the sampling volume required to measure 0.3 DAC.
2) Potential
movement of the workers in and out of the area with the highest airborne
radioactivity.
3.5.22 Perform
the following steps when setting up the personal air sampler for use:
a. Attach
the pump to the worker using the belt that is provided.
b. Secure
the tygon tubing with the air sampler head over the worker’s shoulder and neck.
c. Locate
the sampler head within 10 inches of the workers nose and mouth.
d. Secure
the air sample head to the worker by tape or other means making sure not to
restrict air flow through the tube.
e. Turn
the pump on and verify the flow rate is within specification.
f.
Inform the worker to leave the work area if they
believe the pump is turned off for more than 30 seconds or is otherwise
malfunctioning.
g. Document
the person’s name and any other identifying information on the site-specific
document (e.g. air sample bag or an accompanying form) along with the time the
pump was turned on and any other pertinent information such as flow rate, job
location time, etc.
3.5.23 Perform
the following steps when removing a personal air sampler:
a. Turn
off the sampler pump.
b. Remove
the air sampler head, tygon tubing, and pump from the worker.
c. Remove
the air sample from the air sample head and place in the air sample bag or
petri dish as required by site procedures.
d. Use
site-specific procedures and forms to record parameters and analyses.
3.6
Analyze a Particulate Air Sample Filter
3.6.24 Use
Attachment 1 to record air sample parameters that are required to calculate
airborne concentrations.
a. Use
site-specific forms to record sample parameters from a personal air sampler to
calculate a potential intake.
3.6.25 Use
Attachment 1 and the instructions in Attachment 2 to analyze air sample filters
and compare airborne concentrations to Derived Air Concentrations (DAC).
5.13 EPRI
Alpha Monitoring Guidelines for Operating Nuclear Power Stations, Revision 2,
EPRI Technical Report 3002000409, August 2013
5.14 NRC
Information Notice No. 86-43: Problems
with Silver Zeolite Sampling of Airborne Radioiodine
5.15 NRC
Regulatory Guide 8.25, Air Sampling in the Workplace, Revision 1, §3.1
5.16 NISP-RP-13,Radiological Protection Glossary
5.17 NISP-RP-04,Posting and Labeling of Radiological Areas
5.18 NISP-RP-10,Radiological Job Coverage
5.19
Attachment 1: Airborne Radioactivity Calculation Worksheet
– Sample
Each parenthetical number on the worksheet corresponds
to instructions in Attachment 2.
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Section I:
Air Sample Collection Information |
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(1) Location/Description: |
RWP: |
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(2) |
Air Sampler
Type: |
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Survey #: |
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Serial Number: |
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Sampled by: |
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Cal Due Date: |
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(3) Reason for Sample: |
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(4) |
¨ Grab Sample |
¨ Continuous Sample |
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(5) |
¨ Breathing Zone |
¨ Work Area |
¨ General Area |
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(6) |
Sample
Start |
Sample Stop |
Total Time (minutes) |
Flow Rate |
Total Volume |
Total Volume (ml) |
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Stop |
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ft3 |
x 28,320 = |
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Time: |
Time: |
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lpm |
liters |
x 1,000 = |
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(7)Sample Collected From: |
¨ Alpha Level 1 Area |
¨ Alpha Level 2 Area |
¨ Alpha Level 3 Area |
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(8) |
NOTE: Use a TRU Multiplier only if an estimate of
fDACTotal is needed in
lieu of completing alpha analysis. |
βγ/α Ratio: |
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TRU Multiplier: |
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(9) |
Analyses Requested |
¨ Gamma spec (Part and/or Iodine) |
¨ Noble Gas |
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¨ Beta-Gamma Analysis |
¨ Alpha Analysis |
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Section II:
Beta-Gamma (βγ) Analysis |
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βγ
Analysis |
Date/Time |
ncpm |
dpm |
fDACβγ |
RPT Initials |
Serial Number |
Cal. Due Date |
Eff |
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(10) |
1.0
Initial |
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2.0
(11) |
3.0
Follow-Up |
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(12) fDACTotal if Needed in Lieu of Alpha Analysis (fDACβγ X TRU Multiplier): |
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Section III:
Alpha (α) Analysis |
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4.0
α Analysis |
Date/Time |
ncpm |
dpm |
Βγ/α Ratio |
fDACα |
RPT Initials |
Serial Number |
Cal. Due Date |
Eff |
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5.0
(13) |
6.0
Initial |
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7.0
(14) |
8.0
Follow-Up |
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9.0
(15) |
10.0 Rn Comp |
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(16) |
Long-Lived |
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Section IV: Final Summary |
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(17)fDACβγ
= |
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(18)fDACα
= |
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(19) fDACTotal = |
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(20)Reviewed
by: |
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Approved by: |
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Print/Sign |
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Print/Sign |
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Attachment 2: Instructions to Complete Airborne
Radioactivity Worksheet
Section I:
Air Sample Collection Information
Complete this section for each air sample except samples
from personal air samplers. Use
site-specific procedures and forms for recording parameters and analyses of
personal air samples.
(1) Record
sufficient information to describe where the sample was taken, the RWP number
for the work at the sampling location, the survey number documenting the final
results, and the printed name of the RP technician collecting the sample.
(2) Record
the type of sampler, e.g. hi-volume, lo-volume, gas, etc., the serial number of
the sampler, and the calibration due date.
(3) Record
the reason for the sample, e.g. job coverage, system breach, HEPA maintenance,
etc.
(4) Check
the applicable box for one of the following:
a. Grab
Sample – A short duration sample to measure the airborne concentration at a
single moment in time.
b. Continuous
Sample – A sample taken to measure the average airborne radioactivity over a
period of time; continuous samples are typically collected from 30 minutes to
several hours.
(5)
Check the applicable box for:
a. Breathing
Zone
b. Work
Area Sample
c. General
Area Sample
(6)
Record the sample collection data required to
determine the total volume of air sampled.
Record “n/a” if a sample pump was not used, e.g. a noble gas grab
sample.
a. Record
the date and time for starting and stopping the sampler and the total time for
sampling in minutes.
b. Record
the flow rate at the start and end of the sampling period. Record the average flow rate of the sampler.
c. Calculate
and record the total volume sampled.
d. Record
the total volume in ml.
(7)
Check the box showing the classification of the
area where the sample was collected: Alpha Level 1 Area, Alpha Level 2 Area, or
Alpha Level 3 Area.
(8)
Record the βγ/α Ratio
and, if an estimate of fDACTotal is needed
in lieu of completing an alpha analysis, the Transuranic (TRU) Multiplier
applicable to the air sample. These
values may be obtained using Attachment 3 or provided by RP supervision based
on site characterization. The Total DAC
is determined by multiplying the fDACβγ by the TRU
Multiplier. A TRU Multiplier is
derived as follows.
(9) Use
this section to check the types of analysis needed. Samples may be submitted to a laboratory for
all analyses or technicians may complete all or portions of the Beta Analysis
and/or Alpha Analysis sections prior to submittal to the laboratory.
Attachment 2: Instructions to Complete Airborne
Radioactivity Worksheet (continued)
Section II:
Beta-Gamma (βγ)
Analysis
Use this section to document an initial screening
of the sample using a beta detector with either a scaler or ratemeter. This section is not required if the sample
has been submitted to the laboratory for gamma spectroscopy.
(10) Record
data in the row designated for an initial βγ analysis to record data from the first analysis performed
after the sample was collected.
a.
Record the following information:
·
Date and time of the analysis
·
Serial number of the instrument
·
Calibration due date
·
Efficiency factor (use 0.1 for a pancake GM
detector unless otherwise instructed by RP supervision)
b. If
using a gas flow proportional counter or other instrument, record the efficiency
factor posted with the specific instrument.
c. Record
the net counts per minute (ncpm) above background. Ensure background is less than 200 cpm when using a pancake GM detector.
·
Record ND (for not detected) if there is not an
observable count rate above background or scaler counts are below the MDA value
posted with the instrument.
d.
Divide the observed ncpm by the efficiency and
record the dpm value.
·
Record ND if there is not an observable count
rate above background or scaler counts are below the MDA value posted with the
instrument.
e.
Use the following equation to calculate fDACβγ
if activity is detected above background.
RP supervision may direct using a different DAC value based on the plant
source term. Use an equation as directed
by RP supervision.
|
where: |
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0.0222= |
(2.22e+6 dpm/µCi) X (1e-8 µCi/ml) |
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1e-8= |
DAC value for Co-60 |
f. If
fDACβγ
is ≥ 0.3 DAC, notify RP
supervision and collaborate to accomplish or verify the following:
·
If radon interference is suspected during field
analysis, consult RP supervision to determine if follow-up actions should be
delayed until a radon-discriminating analysis is completed.
·
Ensure the area is properly posted as an
Airborne Radioactivity Area per NISP-RP-04.
·
Submit the sample and worksheet to the
laboratory for gamma spectroscopy analysis with a priority as established by RP
supervision.
·
Determine cause and corrective action if the
airborne radioactivity was not anticipated.
Attachment 2: Instructions to Complete Airborne
Radioactivity Worksheet (continued)
g. Complete
the following Section III for alpha analysis for any one of the following
conditions:
·
The fDACβγ is ≥ 1.0.
·
The
sample was from an Alpha Level 2 Area and an alpha analysis is required as
determined using Attachment 4.
·
The sample was from an Alpha Level 3 Area.
(11) Record
data in the row designated for a follow-up βγ analysis as an option to determine if the initial results
were impacted by the presence of radon daughters.
a.
Perform the follow-up analysis approximately 30
minutes to 1 hour after the initial analysis.
Perform the same steps as described for an initial analysis.
b.
Any observed decay indicates the presence of
short-lived radon daughters. The
half-life of radon daughters ranges from 35 to 40 minutes depending on the time
after sample collection.
c.
If the results are affected by radon daughters,
submit the sample and worksheet to the laboratory for analysis using gamma
spectroscopy or alternative with a priority as established by RP supervision.
(12) If
the sample was collected in an Alpha Level 2 or 3 Area, multiply fDACβγ
by the TRU Multiplier to approximate fDACTotal if an
estimate is needed in lieu of completing alpha analysis.
Section
III: Alpha (α) Analysis
Use this section to document an analysis performed
with an alpha detector using a scaler. This section is used to determine the βγ/α ratio for a sample collected from an Alpha Level 3 Area,
Alpha Level 2 Area, or an Alpha Level 1 Area when fDACβγ is ≥
1.0.
(13) Record
data in the row designated for an initial α analysis to record data from the first analysis performed
after the sample was collected.
a.
Record the date and time of the analysis, the
serial number of the instrument, the calibration due date, and the initials of
the RP technician performing the analysis.
b.
Record the efficiency factor as posted with the
instrument. Ensure the efficiency factor
includes the self-absorption factor for the filter media being analyzed.
c.
Record the net counts per minute (ncpm) above
background.
·
Record ND (for not detected) if counts are below
the MDA value posted with the instrument.
d. Divide
the observed ncpm by the efficiency and record the dpm value.
·
Record ND if counts are below the MDA value
posted with the instrument. No further
analyses are required. Record less than
0.1 for values of fDACα.
e.
Calculate and record the βγ/α Ratio by
dividing the dpm value from the βγ
Analysis (or gamma spectroscopy results) by the dpm value from the α Analysis.
Attachment 2: Instructions to Complete Airborne
Radioactivity Worksheet (continued)
f. Use
the following equation to calculate fDACα. RP supervision may direct using a different
DAC value based on the plant source term.
Use an equation as directed by RP supervision.
|
where: |
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6.66e-6= |
(2.22e+6 dpm/µCi) X (3e-12 µCi/ml) |
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3e-12= |
DAC value for Am-241 |
(14) Record
data in the row designated for a follow-up analysis using the same steps as
described for the initial α
analysis to determine if short-lived radon daughters are present. If radon daughter contribution is suspected,
perform this follow-up count 1 to 2 hours after the initial count. If radon daughters are interfering with the
analysis, complete the next step.
(15) If
radon daughters are interfering with the analysis, the actual contribution to
the count from alpha emitting transuranics may be estimated by using one or
more of the following methods:
a.
A counting instrument may be used that is
designed to discriminate the radon contribution.
b.
Plant-specific software such as a spreadsheet
may be used to calculate the radon contribution.
c.
A subject matter expert may be assigned to
perform the evaluation.
d.
The following equation may be used to estimate
the transuranic concentration from the follow-up count on line 15. Consult with RP supervision on desired decay
times between counts.
|
where: |
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|
|
ncpmtr= |
Net count rate due to alpha emitting transuranic nuclides |
|
|
ncpm1= |
Net count rate from initial analysis |
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ncpm2= |
Net count rate from follow-up analysis |
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Δt= |
Time between analyses, minutes |
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0.017= |
Decay constant for a 40 minute half-life, min-1 |
|
e.
Record the radon compensated results (ncpmtr)
in the ncpm column on line 15. Complete
line 15 using the radon compensated results.
This is only an estimate and should not be used for record values. Only the results after full radon decay
should be used for record results.
(16) Record
long-lived analysis data after the sample has decayed ≥ 72 hours using the same steps as described for the initial α analysis. This analysis should provide the basis for
the record value of fDACα if radon daughters interfered with the
initial analysis.
Attachment 2: Instructions to Complete Airborne
Radioactivity Worksheet (continued)
Section
IV: Summary
This section is used
to record the final DAC values from the sample as described below.
(17) Record
the value for fDACβγ as follows:
a.
Record gamma spectroscopy results if
performed. Attach the gamma spectroscopy
printout or reference the analysis reference number used by the site.
b.
Record the results from the beta-gamma analysis
from Section II if gamma spectroscopy was not performed.
c.
Record ND if βγ activity was not detected.
(18) Record
the value for fDACα as
follows:
a.
Record less than 0.1 if alpha activity was not
detected.
b.
If alpha activity was detected, record the
long-lived results from (16).
c.
Record n/a if alpha analysis was not performed.
(19) Record
the fDACTotal by summing the values from (18) and
(19).
(20) Submit
the results for review and approval.
Immediately notify RP supervision to alert them to any one of the
following conditions:
a.
The βγ/α Ratio is less than 30,000 in an
Alpha Level 1 Area
b.
The βγ/α Ratio is less than 300 in an
Alpha Level 2 Area
c.
The βγ/α Ratio is less than or equal to 50
in an Alpha Level 3 Area
d.
Beta-gamma activity was not detected but alpha activity was detected.
Attachment 3: TRU Multiplier Based on Co-60 and Am-241
Attachment 4: Alpha
Analysis Requirements for Samples from Alpha Level 2 Areas
Purpose
This attachment
provides instructions for determining when a particulate air sample from an Alpha
Level 2 Area must be analyzed for alpha emitting transuranics; three options
are available as follows:
Option
1 – Perform alpha analysis on all particulate air samples or on all
particulate air samples with a measured fDACβγ greater than a
site-specified value, e.g. 0.025 DAC.
Option
2 – Perform an alpha analysis on a particulate air sample that indicates a
Total DAC ≥ 1.0 DAC when
applying a TRU Multiplier as determined by site characterization.
Option
3 – Perform an alpha analysis on a particulate air sample that indicates a
Total DAC ≥ 1.0 DAC assuming
the most restrictive alpha emitter (e.g. Am-241) and the most restrictive beta
emitter (e.g. Co-60 or Cs-137) expected in the nuclide mixture.
RP supervision at each
plant is responsible for directing supplemental RP personnel on the acceptable
options to use based on plant procedures.
Option 1
For particulate air samples from Alpha Level 2
Areas meeting site-specific criteria, record both the beta analysis results and
the alpha analysis results on Attachment 1.
Use these values to determine the Total DAC.
Option 2
1.0 Multiply
the fDACβγ by the TRU Multiplier provided by site procedures, RWPs
and/or ALARA Plans.
2.0 If
the Total DAC is ≥ 1.0,
perform an alpha analysis and record the results using Attachment 1.
Option 3
1.0 If
this option is used, the βγ/α Ratio for the area where the air
sample was collected will be documented in plant procedures, ALARA planning
documents, and/or the RWP.
1.1
The βγ/α Ratio is normally determined
based on the nuclide mixture collected from loose surface contamination.
2.0 Record
the βγ/α Ratio on Attachment 1.
3.0 Use a graph to determine if alpha analysis
is required as described below. Graphs
may be based on assuming a Co-60 and Am-241 mixture (shown below) or based on
actual characterization of the nuclide mixture.
3.1
Locate the intersection of the following:
a. The
βγ/α Ratio for the area where the air sample was collected.
b. The fDACβγ measured from the air sample.
3.2
If the intersection is to the left of the line,
alpha analysis is required. Document the
analysis results on Attachment 1.
3.3
If the intersection is to the right of the line,
alpha analysis is not required.
Attachment 4:
Alpha Analysis Requirements for Samples from Alpha Level 2 Areas (continued)
Attachment 5: Sample Particulates and Iodine Using Standard
Air Sampler
1.0 Obtain
equipment listed below as needed:
·
Sample head
·
Particulate filter
·
Iodine Cartridge
·
Air Sampler
·
Sample label
·
Poly bags or equivalent
·
Sample tubing
2.0 Check
rubber O-rings on sampling head to ensure positive seals as required for the
model of head being used.
3.0 Place
filter paper into filter holder with collection side toward sample intake.
If the collection side is not indicated by the manufacturer, mark the
collection side with a pen or marker so that any subsequent analyses can be
performed on the collection side.
4.0 If
iodine sampling is required, then place new iodine cartridge into holder with
arrow pointing with direction of air flow. A dummy cartridge may be used if iodine sampling is not required
and the air sampler has been calibrated with an iodine cartridge.
5.0 Set
up sampler as shown below.
6.0 Place
sample inlet in a location representative of the desired sample; a location that is far enough from a contaminated surface
to prevent pulling surface contamination into the sample media.
Attachment 5: Sample Particulate and Iodine Using Standard
Air Sampler (continued)
7.0 For
grab samples, estimate the time required to obtain the minimum volume by
dividing the required sample volume by the flow rate; ensure units are
consistent and convert as needed.
CAUTION
Do not operate a sampler
where hydrogen may be approaching the Lower Explosive Limit (e.g. 2% to 4% H2). Notify industrial safety personnel as needed
for confirmation.
8.0 Turn
on the sampler and verify, or adjust, the flow rate to be within 20% of the
calibrated flow rate.
9.0 When
the predetermined sample time or longer has passed, then stop the sampler and
record the information as listed in section (6) on Attachment 1.
10.0 Remove
sample collection media and place in
a bag, exercising care to prevent cross contamination.
11.0 Determine
the sample volume by multiplying the sampling time by the observed sample flow
rate; ensure units are consistent and converted as needed.
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