Aerosols deposition qualification of Stack Monitors
for Research Reactors (RR) & Medical Isotope
Production Facilities (MIPF)
Eduardo Nassif – INVAP S.E. – Bariloche - Argentina
Fabian Rossi - ANSTO - Australia
ARMUG 2014 – NPL – 11/19/2014
The Real Emissions…determining Aerosols Deposition
Context - Relevance of Aerosols Deposition (& Iodine Plate Out ) on
Sampling lines of Stack Monitors
 On measuring stack effluents in nuclear facilities, aerosols deposition and iodine plate
out on sampling lines should drive relevant attention in order to optimize design of
sampling lines, minimize sample losses and improve accuracy (on determination of
stack releases).
 A number of considerations on sampling lines geometry, analysis of suitable materials
and flow rate ranges shall be taken into account.
 Design recommendations and guidance are defined on Standards – like, for instanceANSI 13.1 and M11 (see References below on this presentation). This lead designers to
often focus their attention on monitor´s location and disposition inside the plant, and
reactor´s stack sampling lines design.
 While this a rather common practice to be considered when connecting air effluent
monitors to process (stack), less attention is driven regarding design and qualification of
monitor´s internal sampling lines, related to aerosol deposition and iodine plate out
effects.
ARMUG 2014 – NPL – 11/19/2014
The Real Emissions…determining Aerosols Deposition
Scope : Main goals..

To determine actual penetration factors inside monitor´s sampling lines. This is
relevant, since may affect measurement accuracy when estimating stack
emissions.

In addition to review calculations on deposition effects expected for specific
connections of stack monitors to process, an experimental method to
quantify relevance of deposition effects inside monitoring equipment – in
comparison with the effects observed on main connection to process- is
described.

Previous analysis is complemented with a review of Iodine Plate-Out
effects on stack monitor´s sampling lines is presented.
ARMUG 2014 – NPL – 11/19/2014
The Real Emissions…determining Aerosols Deposition
Stack Monitors Installation Requirements
 Many RMS suppliers produce and install Stack Eflluent monitors on (new or upgraded)
nuclear facilities. Different facilities do have specific air sampling requirements.
 Due to quite diverse lay-out arrangements, etc…), installation requirements for
sampling lines may be quite different.
 Installation in already existing upgraded plants usually do present more complex
restrictions for sampling line connections from monitoring units up to the stack.
 Specific customer´s requirements does impose also additional restrictions on
monitoring units themselves.
(Example: closed structures may be required as prevention for shower spreads being
installed in the vicinity of the equipment as part of fire systems..), while in other cases
“open” racks can be used, thus giving other internal sampling lines design
opportunities.
 In the following slides, some remarks on these design options, considered for several
equipment installed by our company at different facilities are presented...
ARMUG 2014 – NPL – 11/19/2014
Installation & Monitoring Requirements
Real Time – Off-Line Automatic Stack Effluents Surveillance
(some examples)
 RPF/ETRR-2 Radioisotope Production Facility (Egypt)
 OPAL Nuclear Research Reactor (Australia)
ARMUG 2014 – NPL – 11/19/2014
Stack Effluents & Air Ventilation Radiation Monitors
(Most Usual Features)

ISOKINETIC SAMPLING

STACK EMISSIONS IN RR

STACK EMISSIONS IN MIPF * (High Activity - Pulsed «batch» emissions follow-up)

PARTICULATE –IODINE – NOBLE GAS independent channels

NG CHANNEL: GROSS β - GROSS γ DETECTION and γ SPECTROMETRIC CAPABILITIES
(41Ar – 133Xe and other specific measurement channels)

GROSS β - GROSS γ DETECTION FOR AEROSOLS (currently α/β measurement requirements)

131I

DETECTORS: Use of plastic scintillators
DETECTION ON IODINE CHANNEL
last generation Lanthanum halide scintillators
CdTe Solid State detectors – Si PIPS

4 User´s Interface Communication Levels (Local x 2 – Remote x 2)

CUSTOMIZED – PROCESS ORIENTED SOFTWARE INTERFACE

PROCESS CUSTOMIZED STRUCTURE & SAMPLING SYSTEM*
ARMUG 2014 – NPL – 11/19/2014
Typical Internal Architecture (possible Options)
Structural
Interconnection & Communications (example)
OPEN GEOMETRY SAMPLING RACK
STANDARD 19in. RACK WITH TOUCH
SCREEN LOCAL INTERFACE
OR..
SEISMIC QUALIFIED CUSTOM STRUCTURE – after IEEE 1E 344
IP 65 COMPLAINING - WATER TIGHT -
ARMUG 2014 – NPL – 11/19/2014
The Real Emissions…determining Aerosols Deposition
2 Main Tracks to be considered..
Stack to Monitor
Monitor´s internal
sampling lines
Adjustment of Penetration
Factors should be available
within Monitor´s Software
capabilities
ARMUG 2014 – NPL – 11/19/2014
Determining Aerosols Deposition….Stack to Monitor
From Stack to Monitor
...(by calculations)
INPUT DATA
Vertical section
(stack level +37 to llevel +16) 21 m
Horizontal section
3.7 m
Elbows
4 x 90
Pressure
101.325 Kpa
Temperature
300 K
Diameter of the aerosol particle to be considered
10 m*
* according to ANSI 13.1, pages 29 and 39
Shorter sampling lengths between Stack
and Monitor is achievable when installing
the monitor at higher reactor building
levels….but…
..this implies higher seismic requirements
impact on structure and internal sampling
lines design
ARMUG 2014 – NPL – 11/19/2014
The Real Emissions..determining Aerosols Deposition
Stack to monitor sampling line - Aerosols Deposition mechanisms
 Gravitational settling: Significantly only on horizontal sections or on an angle
above 30 degrees with respect to the vertical
 Brownian diffusional deposition: Generally quite low for velocities above 1m/s
 Turbulent inertial deposition: Quite significant and rising with velocity at an
exponent close to 2.6, depending on the correlation
 Electrostatic deposition: It depends on the electrostatic load accumulating
on the piping
 Thermophoretic deposition: Registered when there are temperature
gradients between walls and flow, or between flows at different
temperatures
 Diffusiophoretic deposition: Due to aerosol concentration gradients in the
same fluid, it is negligible in turbulent rates and in those of low deposition by
other mechanisms
ARMUG 2014 – NPL – 11/19/2014
The Real Emissions..determining Aerosols Deposition
Stack to monitor sampling line - Aerosols Deposition mechanisms
Penetration of the Piping System as the result of the individual penetrations of each fitting
and straight section for each mechanism.
total  i , j
i, j
Where
i , j
is the penetration of fitting i for deposition mechanism j
Correlations are used for the entire sampling piping that calculate separately each
mechanism and distinguish elbows, contractions and expansions as global deposition.
Deposition on bends may be calculated through the following equation when the
curvature radius – inner diameter ratio is equal to or above 5.
bend  e2.823 Stk 
where,
 is the elbow angle.
Stk = Stokes Number
ARMUG 2014 – NPL – 11/19/2014
The Real Emissions…determining Aerosols Deposition
Stack to monitor sampling line - Aerosols Deposition mechanisms
Calculations being considered/performed on all straight sections after the specific
mechanisms
Mechanism
Calculation being performed
Yes, for all non-vertical sections -main
mechanism-
Gravitational settling
Turbulent inertial deposition
Yes
Brownian diffusional deposition
Electrostatic deposition
Thermophoretic deposition
Diffusiophoretic deposition
Yes, for verification purposes
No: as metallic pipelines grounded through
anchors are considered and fluid is air with
50% +/- 10% controlled humidity.
No: as it is considered that there are no
RELEVANT temperature gradients on the
pipeline
(hence effects are negligible: < 0.1%) .
No: only one gas (air) -perfectly mixed and
uniform - is present in the sampling line
ARMUG 2014 – NPL – 11/19/2014
The Real Emissions…determining Aerosols Deposition
Stack to Monitor sampling lines
Different sampling line design alternatives being analyzed
Item
1
i = 0.0221m (25.4mm, BWG16,
e=1.65 mm)
Q = 75 l/min
U = 3.26 m/s
i = 0.0221m (25.4mm, BWG16,
e=1.65mm)
2
Q = 65 l/min
U = 2.85 m/s
i = 0.0316m (34.9 mm, BWG16,
e=1.65mm)
3
Q = 94 l/min
U = 2 m/s
i = 0.0348m (38.1mm, BWG16,
e=1.65mm)
4
Vertical
section
Horizontal
section
Elbows
Reynolds fluid (Ref)
4608
4608
4608
Gravitational penetration
1
0.82
-
Diffusional penetration
0.999
0.9999
-
Turbulent penetration
0.854
0.972
-
Total ( i )
0.853
0.797
0.448
Reynolds fluid (Ref)
4029
4029
4029
Gravitational penetration
1
0.798
-
Diffusional penetration
0.999
0.9999
-
Turbulent penetration
0.904
0.982
-
Total ( i )
0.903
0.783
0.49
Reynolds fluid (Ref)
4042
4042
4042
Gravitational penetration
1
0.799
-
Diffusional penetration
0.999
0.9999
-
Turbulent penetration
0.983
0.997
-
Total ( i )
0.982
0.796
0.70
Reynolds fluid (Ref)
4118
4118
4118
Gravitational penetration
1
0.802
-
Diffusional penetration
0.999
0.9999
-
Turbulent penetration
0.988
0.998
-
Alternative
Q = 105.6 l/min
U = 1.85 m/s
i = 0.03339m (38.1mm, BWG14,
e=2.11mm)
5
Q = 100 l/min
U = 1.85 m/s
Total ( i )
0.987
0.800
0.74
Reynolds fluid (Ref)
4011
4011
4011
Gravitational penetration
1
0.797
-
Diffusional penetration
0.999
0.9999
-
Turbulent penetration
0.988
0.998
-
Total ( i )
0.987
0.795
0.743
ARMUG 2014 – NPL – 11/19/2014
Total
0.305
0.346
0.547
0.580
0.583
The Real Emissions..determining Aerosols Deposition
(Aerosols) Stack to Monitor sampling: Conclusions
 Case Item 5 : A tube of a 38 mm diameter and BWG 14 (ID 33.88mm)
at a nominal flow of 100 l/min was adopted.
 Global penetration of 58.3% -reached with previous adoption-, is
above the 50% deemed as sufficient design value for the transfer of
aerosols with a 10m diameter.
ARMUG 2014 – NPL – 11/19/2014
Stack To Monitor Sampling Lines.. Iodine Plate Out..?
The following equation given by ANSI N13.1-1999, Annex C (C-1) is
Vd: Deposition speed in [m/s] interpolated
used to calculate iodine plateout:
iodine  e
Species
I2
HOI
CH3I
V L
4 d
U dt
to 50% rel. humidity
L: Total Length [m]
U: Air Flow speed [m/s]
dt: Piping diameter [m]
The calculation considers fixed length L= 25m
Inner
diameter 0.0221 0.0221
0.0316
[m]
Velocity
3.26
2.85
2.00
[m/s]
Vd (50 %
Penetration iodo
humidity)
1.43E-03
0.1041
0.1374 0.1033
m/s
3.85E-05
0.9817
0.9914 0.9870
m/s
7.50E-08
0.9999
0.9999 0.9999
m/s
0.03388
1.85
0.1085
0.9810
0.9999
ARMUG 2014 – NPL – 11/19/2014
Stack To Monitor Sampling Lines.. Iodine Plate Out..?
(Iodine) Stack to Monitor sampling lines: Conclusions
 All penetrations are above 50%, except for chemical species I2, in which values are
quite low, mainly as a result of the small Vd (Deposition Speed)* for this species.
 Case Item 5 adopted before, i.e. a tube of a 38 mm diameter and BWG 14 (ID
33.88mm) at a nominal flow of 100 l/min, showed acceptable conditions for Iodine
Plate-Out, for HOI and CH3I species.
* Deposition speed being considered is that reported by M.J. Kabat, “Deposition of Airborne
Radioiodine Species on surfaces of metals and plastic”, Ontario Hydro, mentioned as
reference in standard ANSI 13.1-1999, and corresponding to stainless steel.
ARMUG 2014 – NPL – 11/19/2014
Iodine Plate Out - A look to internal monitor´s sampling lines:
Comparison among Iodine Species
Note here for I2 (Plastic):
 Much LOWER Vd than SS!
 Smaller L than external
 Smaller d than external
Much efficient Penetration!
ARMUG 2014 – NPL – 11/19/2014
The I2 Species: comparison between stack monitor´s
external & internal sampling lines: the I2 Case
Vd: Iodine Deposition Speed [m/s] interpolated
considering 50% de humidity
L: Total Length [m]
U: Air Flow rate [m/s]
dt: Piping diameter [m]
Note here for I2 (Plastic):
 Smaller L
 Smaller d
 Much higher Vd!
Calculations for I2
Vd(I2)
L
U
d
L/( U x d)
ηd
Stack to Monitor
SS 304L
Monitor
internal lines
SS304L
1,43E-03
25
3,26
0,0221
347,0005274
13,74%
1,43E-03
1,42
4,46
0,0195
16,3274692
91,08%
Stack to
Monitor
Monitor
inte rnal
Poliethylene Poliethylene
9,50E-05
25
3,26
0,0221
347,000527
87,65%
ARMUG 2014 – NPL – 11/19/2014
9,50E-05
1,42
4,46
0,0195
16,32746924
99,38%
Monitor´s internal Iodine Plate Out :
(not obvious..?) Lessons learned
 Iodine depositions
parameters.
are
extraordinary
sensitive
to
geometrical
 Using Plastic - instead of SS – dramatic improvements may be reached
when focusing on I2 species…(I2 is «more anomalous» in terms of
deposition on SS..)
 Iodine Plate Out and Aerosols deposition goes in opposite directions in
terms of design for optimum penetration…
(Design helps on finding a compromise .. not an optimum solution..!)
 If I2 were the predominant species,…Plastic should be used instead of
SS...but (because of chemical stability and relative abundance in air),
 I2 is not the most common species for radioactive Iodine, therefore..
…SS is –still- a good relative solution in terms of Iodine penetration.
ARMUG 2014 – NPL – 11/19/2014
Now..how Does Behave the Aerosols Deposition
inside Monitor´s Internal Sampling Lines?
…Experimental Determination needed!!
Ideal representation…..but Complex real Geometry
ARMUG 2014 – NPL – 11/19/2014
The Real Emissions…determining Aerosols Deposition
Monitor´s internal sampling line: Why Experimental Determination….?
..since Monitor´s sampling circuit do present non-regular geometrical arrays…







Non perfectly cylindrical sections (¾” ID Poliethylene Poliethylene pipes).
Valves of different types and sections
Curves
Fittings (7)
Elbows
T – reductions
Adapters
Theoretical calculations & modelling do not bring fully reliable data..
(as may be developed in case of for regular piping sections for stack to monitor sampling
lines).
..Experimental Validation Tool is required for Aerosols Deposition factors determinations
(Similar criteria as in case of calculation of Hydraulic losses in complex
equipment/sampling circuits where experimental validation is current used tool, beyond
finite elements calculations).
ARMUG 2014 – NPL – 11/19/2014
The Real Emissions…determining Aerosols Deposition
Aerosols sampling depositions: Experimental Determinations
 To quantify aerosols deposition from monitor´s flange connection to process (stack
sampling lines), up to the particulate measurement chamber.
 Calibrated Spherical Particles - 5.4* microns diameter are injected at monitor´s inlet.
(* available particle diameter size in occasion of the measurement)
 Quantification is performed using differential weighing technique.
 Simultaneous measurement of particle concentration with APS at monitor´s inlet.
(Aerodynamic Particle Sizer).
 Each measurement comprises a collection filter at monitor´s entrance, and a collection
filter inside particulate measurement chamber.
 More than 30 measurements were conducted.
 Measurements were performed at INVAP´s Testing facilities.
ARMUG 2014 – NPL – 11/19/2014
The Real Emissions…determining Aerosols Deposition
Aerosols sampling depositions: Experimental Array
Particulate generation is performed using a high speed N2 jet
Jet-driven depression sucks and atomizes the particulate suspension
The Measurement Array does include:
 A particle spray generator
 A Heat Exchanger (for water evaporation on water drops attached to the
particle
 A Dryer for absorption of water steam
 A Flow compensation device (between particulate injection flow and
monitor´s air flow)
 An APS (Aerodynamic Particle Sizer)
 Glass Fiber filters fro Aerosols collection
 Injection system components (i.e., N2 cylinder, flowrate meters, valves, etc.)
ARMUG 2014 – NPL – 11/19/2014
The Real Emissions…determining Aerosols Deposition
Aerosols sampling depositions: Experimental Set-Up (schematic)
ARMUG 2014 – NPL – 11/19/2014
The Real Emissions…determining Aerosols Deposition
Experimental Set-Up : Filter Removal at Aerosols Measurement Chamber location
ARMUG 2014 – NPL – 11/19/2014
The Real Emissions…determining Aerosols Deposition
Experimental Set-Up
APS
ARMUG 2014 – NPL – 11/19/2014
The Real Emissions…determining Aerosols Deposition
Measurement Sequence
 A previously weighed filter, is set at the entrance of the monitor to collect aerosols
during a defined time interval.
 After collection and remotion of this filter, another weighed filter is set inside the
monitor at the regular particulate measurement location (without interrupting
particulate generation), so that particulates are collected for a similar (time)
interval.
 Both filters are weighed again,after collection, in order to get by difference the
deposited net mass inside monitor´s internal sampling lines.
 Using APS measurements, the sampling flow rate and the collection time interval,
the total mass being injected is calculated.
 Four measurements were performed: two for mass (monitor´s input and output),
corresponding to filter weighing, and two for concentration (direct measurements
performed with APS at monitor´s inlet).
ARMUG 2014 – NPL – 11/19/2014
The Real Emissions…determining Aerosols Deposition
Results
Several statistical methods were applied to handle experimental data:
 Adjustment by minimum squares
 Minimum Modules Analysis
 Pairing Data Analysis
The results obtained for Aerosols relative deposition, namely the ratio
between Mass Deposition (Md) to the mass at the entrance of the
equipment (Me), lead to:
(Mdep/Me) ~ (14 +/- 5) %
regarded as the “envelope” of the most conservative results brought with
each one of the individual statistical analysis.
ARMUG 2014 – NPL – 11/19/2014
The Real Emissions…determining Aerosols Deposition
Conclusions
Particulate material deposition inside internal sampling lines on Stack Monitors is NOT
NEGLIGIBLE, and should be taken into account for proper estimation of aerosols actual
stack emissions.
Type, Size and materials of internal piping, are indeed a relevant issue on designing Stack
Monitor´s. Plastic is still a good option to be considered on specific cases (with some
remarks on Electrostatic issue and exceptive life if installed outdoors..
Combined together with external sampling lines deposition calculations, characterization
of sample losses inside monitor´s internal circuits may bring an integral picture in order to
get a more accurate adjustment of sample losses by Aerosols Deposition –and Iodine Plate
Out.
(Calculated & Measured) Penetration factors may be integrated into equipment software
and user interface in order to facilitate estimations of real emissions of aerosols coming
out through the stack.
To include strategic sampling points in the system to do predictive maintenance and
calibrations to take into account the variation along the time of the sampling line
performance.
ARMUG 2014 – NPL – 11/19/2014
The Real Emissions…determining Aerosols Deposition
Conclusions (Cont.)
“In situ” adjustments of monitor´s sampling system during life cycle operation can be done,
in order to optimize equipment performance and accuracy.
Optimize the instrumentation to monitoring and control the flow performance. Flow
affects the isokinetic hypothesis at the nozzle. System with smart adaptation to the real
online conditions can be implemented on next generation of instruments –e.g. adaptive
flowFinite element is a very useful calculation tool to predict: best point to install sampling point
–main isokinetic nozzle and test point-, minimum mixing length required, flow patron
alteration under different condition in the stack, ambient changes (wind temperature),
etc.
ARMUG 2014 – NPL – 11/19/2014
The Real Emissions…determining Aerosols Deposition
REFERENCES
 “Aerosol Measurement: Principles, Techniques, and Applications” by Pramod
Kulkarni, Paul A. Baron, Klaus Willeke, Paul A. Baron, Wiley Third Edition - 2011
(2nd. Edition – 2004)
 “Gaseous Radioiodine Deposition Losses in Nuclear Reactor Sample Lines”,
Byung Soo Lee, William A. Jester, Pennsylvania State University, Nuclear
Engineering Department
 “Deposition of Airborne Radioiodine Species on surfaces of metals and
plastic”, M.J. Kabat , Ontario Hydro
 “Monitoring of Radioactive releases to Atmosphere from Nuclear Facilities,
Tech. Ref. M-11 (UK)”.
 “Sampling and Monitoring Releases of airborne Radioactive Substances from
the Stack and Ducts of Nuclear Facilities”. Standard ANSI/HPS N13.1-1999
ARMUG 2014 – NPL – 11/19/2014
The Real Emissions…determining Aerosols Deposition
Aknowledgements

Thanks are due to Mr. Marcelo Caputo and to Mr. Marcelo Gimenez from
Centro Atomico Bariloche (CNEA-Argentine National Atomic Energy
Commission) for technical support on implementation of the experimental
technique
 Thanks are due also to Mrs. Mariana Di Tada and Mr. Román Pino
(INVAP S.E.) for valuable technical discussions
ARMUG 2014 – NPL – 11/19/2014
The Real Emissions…determining Aerosols Deposition
Thank you! …… Questions..?
ARMUG 2014 – NPL – 11/19/2014