RAP Region 4 informal testing on
search equipment
Marsha Beekman - WIPP RAP 4 Team Captain
Robert B. Hayes – WIPP RAP 4 Team Scientist
WIPP Site, Carlsbad, NM 88221
Health Physics Instrumentation Committee Meeting
September 24 - 26, 2012
Introduction
Purpose was to test overall performance for
search equipment based on field conditions.
Intended to support team captain, leader,
and scientist determinations for coupling
equipment with particular missions.
FACTORS
Factors folded into evaluation were interface
and interpretation of instrument response.
Conditions were windy and not compensated
for in user interface (what you see is what
you get) in outdoor clear conditions.
• Direct sunlight may have caused reading difficulty on
some displays
Users allowed to continually look at
instrument if vibration alarms too difficult to
discriminate while walking.
Caveats
We do not claim all other users will get
identical results.
• Our results are approximate at best.
Field conditions could substantially change
the results of this test.
Instruments requiring continual visual
monitoring may not be consistent with some
mission parameters.
• Each user came up with their own criteria
Caveats (cont.)
Results were generated by less than 20
experienced and trained users.
• Performance by users with differing amounts of
training and experience could substantially
change these results.
• Training effectiveness for individual units could
substantially change these results.
• Weather (daylight, wind, rain etc) could
substantially alter results.
• Only Cs137 source tested
PackEye
Thermo Scientific
Alarm - LED indication,
audio or earphone
Power supply
NiMH Rech., 3 days
Neutron detector
2 He-3 1.5”x2”, 2.5 atms.
Gamma detector NBR
50 keV to 3 Mev/>30 cps
PackEye <13 lbs.
HRM (Handheld Radiation Monitor)
(Sensor Technology Engineering, Inc.)
Alarm – Single digit (G N)
LED indication and audio
or vibrating alarm
Power supply - 3 Volt
lithium (2/3A), 1month
Neutron detector
He-3, 8.3 atms., 0.75”x7.8”
Gamma detector
CsI scintillator, 0.5”x1.5”
HRM 8.3”x 2”x1.2”
<1 lb.
LRM
 Alarm – LCD single digit (multi
scaling), audio or vibrate
 Power supply
3 volt lithium 2/3A
8 hrs. (backlight) 24 hrs. without
 Neutron detector
 Gamma detector
Not actual
LRM shown
D-tect
D-tect Systems
Alarm LED, single digit
Power supply – 2 AA,
5,000 hrs.
Neutron - None
Gamma detector
CsI(Na) 0.5” x 1.5”
30 keV – 3 MeV
D-tect
3.9”x 2.7”x1.2”
6.4 oz.
G-N Pager
Polimaster
 Alarm audio and/or vibrate,
dose rate/cps readout
 Power supply AA, 800 hrs.
 Neutron detector
LiI(Eu)
thermal to 14 MeV
 Gamma detector
CsI(Tl)
0.06 MeV to 3 MeV
Unit (without clip)
3.4” x 2.8”x 1.2”
8 oz.
Interceptor
Termo Scientific
 Alarm LED dose rate/cps
 Power supply Li-Ion
rechargeable battery
 Neutron detector
He3, 8 atm., 0.5”x2.6”
 Gamma detector
CZT 0.3”x0.3”x0.15”
25 keV to 3 MeV
ID with spectrum display
Interceptor
4.8”x2.6”x1.2”
14 oz.
Test Configuration
Track had source at 8 foot
offset
Source was not neutron
4 ft spacing
4 ft spacing
Distance markers at 4 foot
intervals out to 24 feet
Users told to simply operate
equipment according to their
training
- all users experienced
Source
4 ft spacing
4 ft spacing
4 ft spacing
Test implementation
Data recorded by independent user.
Not all measurements made on all
instruments by all users.
No attempt was made to correct for user
interface or interpretation of instrument
response.
Data averaged over approach from both
sides (instrument held on left and right
sides).
Initial alarm performance
 Multiple performance
metrics of interest
- First to alarm
- Last to alarm
- Most consistent
performance (lowest s)
 Results show (on average)
comparable initial alarm
distance on all units
 D-Tect most consistent
(reproducible) results
Maximum Alarm Position
 Important in terms of
specifically identifying
source position (max.
response at 0).
 Results presented in
distance from perpendicular
projection of source (not
total distance to source).
 Some configurations can
promote offset maxima
 Interceptor best followed by
the HRM, D-tect and then
GN pager.
Alarm Clear Location
Quick alarm clear can be useful for
identifying source location.
- If alarm continues well after source closest
approach, alarm utility is reduced.
Overall, instruments tend to alarm after the
source .
- Attributed to moving time window to update
and pedestrian motion.
Discussion
• Users tend to prefer items which do not
require continual visual readout
interpretation.
- You need to watch where you are walking
- Situational awareness can be critical
• Instruments known to have the highest
sensitivity had some performance issues due
to interface and instrument interpretation.
- For example, wind interference or lack of
recognizing a vibrating alarm effected
performance results.
Results
Subjective results were also obtained.
- Users overwhelmingly preferred smaller
lightweight detectors.
- Users preferred audible alarms when
attempting to monitor detector during a normal
walk effort.
- Users could improve vibration detection if pager
was worn inside the belt (rather than outside
the belt).
- Normal friction from walking often masked
vibration alarms.
Mission Application
Considerations
Initial detection sensitivity does not favor any
instrument for all field conditions.
In source location, maximum location was biased
differently in certain instruments.
- Backpacks sometimes maximize late.
- Small pager type instruments could maximize
early on opposite hip (consider two detectors).
In some situations, alarm clear ability can be
advantageous.
Metrics by the numbers
• Some users
preferred instruments
based on interface
only
• All instruments had
results within a factor
of 2 on average
• Reproducibility was
of the same order of
magnitude on all
instruments
Instrument
Initial Alarm
Distance
(ft)
CoV
Interceptor
9.8
97%
GN pager
11.2
83%
HRM
13.0
126%
D-tect
13.9
53%
LRM
14.5
110%
Packeye
16.9
56%
Additional testing recommend
• Various sized sources
• Different radiation types and combinations
- Does magnitude of neutron mixing with
gamma cause issues?
- Does mixing of gamma energies cause issues?
• Not in direct sunlight
• Requiring identical readout methods from
all users
Conclusion
• Smaller pagers tend to be preferable for
mission parameters.
- Decision makers can consider these results for
future applications
• Difference is in the ergonomics:
- Size, Weight, Clip, Pouch, Backpack
- Alarming indicators
• Audible, visual, vibration
Thanks
 Special thanks to Mark Sievers for setting up the RAP
meeting/training and all the RAP Region 4 members that
supported this testing effort.
 Questions