1. Evaluation Study of High Purity Germanium (HPGe) based Technology in Detection of Radiation Sources in Container
Ng Bee Ling, Ngoh Li Ee, Gordon Lee, Jerome Koh, Danny Ng, May Ong, Lee Fook Kay
Office of the Chief Science and Technology Officer (OCSTO)
Ministry of Home Affairs, Singapore

2. Scope of Presentation Introduction Study Findings Conclusions
- Objectives
- Detector & Materials
Findings
Conclusions
Further study

3. Steel Cargo Container can provide shielding to radioactive materials
INTRODUCTION
Challenges during Container scanning
- Radiation Portal Monitor (RPM) and many handheld identifiers are used in field operations
RPM : Detection (Plastic scintillator detectors with no ability to resolve gamma peaks)
: High Efficiency/low resolution
: Can “alarm” quite often
Handheld detector : Detection & identification of nuclides
: Isotope identification can be challenging for low level radiation
Steel Cargo Container can provide shielding to radioactive materials

4. INTRODUCTION HPGe detector HPGe field deployment
NaI
Resolution of Th-232 detection, HPGe and NaI detectors side by side. HPGe detector has the ability to resolve the gamma peaks, providing higher resolution detection.
Reduce size, complexity, operating power, cost of electronics
Low power, reliable mechanical cryogenic coolers
HPGe field deployment

5. Study Objective Detector & Materials
To evaluate the potential use of the HPGe detector for cargo container scanning
Detector & Materials
NORMs
HPGe Detector (Falcon 5000®)
ISO 20 foot shipping cargo container
Safe Radioisotope discs

6. (used as masking agents) Antique aircraft camera
Safe Source & NORMs used in Study
Isotope Discs
Emission
Activity
* 1uCi = 3.7 x 104  Bq
Cs-137
Gamma
21.2 µci
(7.84 x 105 Bq)
NORMs
(used as masking agents)
Readings on IdentiFinder (handheld device) at close distance to sources
Identification
(Isotopes)
Soil
0.67 uSv/hr
Th-232/U-232
Rock
36.11 uSv/hr 
Ra-226
Antique aircraft camera
1.01 uSv/hr

7. DIST. BETWEEN DETECTOR & CONTAINER LOCATION OF RADIOACTIVE SOURCE
Test variables A B C
LOCATION OF DETECTOR
Data collected at Location
A, B & C.
DIST. BETWEEN DETECTOR & CONTAINER
20cm and 1m from detector to container.
Study set-up
MASKING WITH NORMs
Buried in soil
Hid under box
LOCATION OF RADIOACTIVE SOURCE
IN CONTAINER
middle
Floor
At end wall, away from container doors

8. Study
Background at Location A,B & C collected (Count time of 3,600s). Measurements were made to aid choosing a standard location to perform environmental background counts during normal operations
Screening was performed on the container with the handheld NaI detector.
The safe source was placed inside the container. No alarm detected B C A

9. Study
Detection capability was evaluated by correct identification of the radiation source placed in different geometries in the container. Count times,300s, 600s, 1200s & 3600s
Each detection was repeated at least twice
Detector user interfaces
Energy Spectrum
Mode for location
NID mode
Dose mode

10. Background Data Many peaks in the unshielded background
Location A
Location B
Location C
Counts
Energy (keV)
Many peaks in the unshielded background
Generally, the background rate at each location is quite similar
However, it was observed that the background at Location B gave a poorer detection sensitivity than Location A and C

11. Common Energy Lines present in the background locations
Background Data
Common Energy Lines present in the background locations
Energy (keV)
Nuclide
Origin
352
PB-214
Uranium Series
583.2
TL-208
Thorium Series
609.3
BI-214
911.1
AC-228
968.9
1120.1
1460.7
K-40
Natural
1764.3
2614.2
Net Count Rate cps
Energy (keV)
Net count distributions from background peaks are subtracted from normal measurements during routine analysis
Principally from K-40, and three natural decay series: Uranium, Thorium and Actinium

12. Position of safe source inside container
Findings
Position of detector
Position of safe source inside container
Masking
Detection Results
Observations A
20cm and 1m from container doors
Middle and floor of container No
Yes
Cs-137 detected within 300s
At end wall, away from container doors
Cs-137 detected at 3600s
20cm from container door
Middle of container
(safe source buried in a box of soil)
No nuclide detected. But Cs-137 was detected within 300s at Location X
(safe source hidden under a box of 20kg soil)
Cs-137 detected at 3600s. X
Container A
Container doors
End wall

13. Findings C Position of detector
Position of safe source inside container
Masking
Detection Results
Observations C
On the mezzanine
(high above container)
Middle and floor of container No
Yes
Cs-137 detected within 300s
At end wall, away from container doors
Cs-137 detected at 600s
Middle of container
(safe source buried in a box of soil)
Cs-137 detected at 1200s
Cs-137 detected at 3600s
(safe source hidden under a box of 20kg soil)
No nuclide detected. But
Cs-137 was detected within 300s at location X  C X
Container

14. Conclusions
HPGe detector can provide information about the presence of γ-radioactivity and isotopes emitting radiation in the cargo container
The distance between the source and the detector could affect scan time required to identify the source. The placement of the detector is an important factor when deploying HPGe detector
In the various masking scenarios, the HPGe detector could identify the radioactive source that was placed in the container
Background collection at the deployment locations is preferred for subsequent background subtraction
Overall, this study has demonstrated that HPGe detector can accurately identify and ascertain if radiological dangers are present

15. Further Study
To test out the capability of the technology with other isotopes/mixed isotopes
Optimizing the placement of the detector using a customized mobile cart

16. Acknowledgements Office of the Chief Science and Technology Officer
Oh Hue Kian
Su Hui Yun
Goh Jia Feng
Phua Xu Mei
Zhang Jinhua
SECOM (Singapore) Pte Ltd
Samson Yang
Deon Lim
CANBERRA
Greg Landry, CHP
Jonathan Coleman-Zheng