RAP Region 4 informal testing on search equipment

Marsha Beekman - WIPP RAP 4 Team CaptainRobert B. Hayes – WIPP RAP 4 Team Scientist

WIPP Site, Carlsbad, NM 88221 Health Physics Instrumentation Committee MeetingSeptember 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 - NoneGamma detector

CsI(Na) 0.5” x 1.5”

30 keV – 3 MeV

D-tect3.9”x 2.7”x1.2”6.4 oz.

G-N Pager Polimaster

Alarm audio and/or vibrate,

dose rate/cps readoutPower supply AA, 800 hrs.Neutron detector

LiI(Eu)

thermal to 14 MeVGamma detector

CsI(Tl)

0.06 MeV to 3 MeV

Unit (without clip) 3.4” x 2.8”x 1.2”8 oz.

InterceptorTermo 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

Interceptor4.8”x2.6”x1.2”14 oz.

Test Configuration

Track had source at 8 foot offset

Source was not neutronDistance markers at 4 foot

intervals out to 24 feetUsers told to simply operate

equipment according to their training­ all users experienced

Source

4 ft spacing

4 ft spacing

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