1. Physical Searches for Orphan Sources

2. Introduction By the end of this module students will be able to:
Describe the types of physical searches
Develop a prioritized plan for a physical search
Describe the personnel that comprise the search team and their responsibilities
List the equipment needed
Define assessment and action levels
Describe how the search is performed
List some criteria for stopping a search

3. Overview Types of physical searches and when to perform them
Planning and conducting searches in such a way that:
maximizes the chances of finding sources
uses resources and time efficiently
maintains the safety of the search team
Knowing when to stop a search

4. Physical Searches
Involve one or more persons trying to locate radioactive sources visually and with radiation detection equipment
Are generally performed:
As a search for a specific missing source or when a source is suspected to be in an area
After an administrative search indicates a need
Routinely to provide assurance that no additional unknown sources exist or are not entering an area

5. Passive vs. Active Searches
Passive Searches:
Detectors and people stationary
Placed at choke or nodal points to detect any sources passing by
Active Searches
Personnel with mobile detectors move to a likely location for an orphan source
Systematically search the location
This module focuses on active searches

6. Routine vs. Specific Searches
Often involve passive, portal searches
Can be active during regular inspections
To provide assurance that all sources are known
Wide area routine active searches without cause are not usually cost effective
Specific:
After an administrative search indicates the possibility of an orphan source
When a source is known to be missing or injuries are discovered
Similar processes except for resources and urgency involved

7. Search Planning

8. Elements of a Search Plan
Objectives
Boundaries of search (geography and time)
Radionuclide(s) being sought
Monitoring methods (hand, vehicle, aerial)
Limits of detection for instruments available
Procedures for dealing with found sources
Responsibilities of parties involved
Provision of staff, equipment and finances

9. Practical Planning Steps
Develop a prioritized list of sites to search
Determine search team membership
Ensure all team members have the proper training
Obtain all materials and equipment needed
Determine recovery, storage or disposal options
Obtain approval for search and source movements from the relevant authorities and facility owner

10. Search Locations Last known location of missing source
First priority is within boundaries of facility
Then retracing sequence of events leading to source becoming missing
If not found, expand to include other areas
Check transportation through likely areas
Search sites can also be selected based on results of an administrative search

11. Search Limitations Geographic boundaries Weather constraints
Search boundaries
Weather constraints
Practical constraints
Equipment limitations
Site access restrictions
Time or funding limits

12. Search Team Members: Team leader Communications co-ordinator
Radiation safety officer
Search personnel trained to use radiation detection equipment
Local guide (if needed)

13. Search Team Need or provide training in: Preparation Search procedures
Source securing, storage and transfer procedures
Health and safety precautions
Preparation
Equipment and material procurement
Transfer sample plan onto search maps or GPS

14. Search Team Responsibilities: Conduct searches
Record all readings on search maps
Take digital photos of site, buildings, devices, sources
Locate and temporarily secure found sources
Assist in packaging and transporting these sources to storage or disposal facilities
Document search efforts

15. Preparation for a Specific Search
Conduct briefing
Equipment
Procedures, including:
Radiation safety
Search
Contamination control
Develop safety plan
Dose limits
Turn back dose rates
Integrating dosimeters and limits

16. Preparation for a Specific Search
Develop search information
Search plan transferred to site search maps
Site history
Radionuclides expected
Establish communication plan
Cell or satellite phones
Radios
Call-in times
Stop time

17. Preparation for a Specific Search
Gather materials and supplies
Radiation safety references
Contamination control materials
Consumables
Food and water

18. Preparation for a Specific Search
Check radiation detection instrumentation:
Appropriate for radionuclides that may be encountered
Calibrated
Pre-operational checks completed
Efficiencies for radionuclides that may be encountered
Gather equipment/materials for source packaging/ transportation

19. Equipment Limitations
Ability to detect the type of radiation emitted by the radioactive source being sought
The dose or count rate that can be distinguished from background by a particular detection system
Detector geometry and efficiency
Counting time
Background radiation variability
User technique and ability

20. ?
Decision Rule
When should further investigation of alarms or variations in dose/count rate be performed?
Recommended at 2 or 3 times background radiation level
Some search instruments do not provide indication of counts or dose rate and only give an alarm – alarms should to be investigated using other instrumentation

21. Use of Assessment and Action Levels
Assessment level
Two times background rate:
Stop and let the meter stabilize
Action level
Three times background rate:
“Hot spot” discovered
Stop and evaluate further

22. Onsite Preparations Select background measurement area
Determine background count rate
Calculate assessment and action levels
Two times background rate (assessment level)
Three times background rate (action level)

23. Onsite Preparations
Team leader verifies assignments for team members and establishes call-in times
Walk around the site:
Look for suspicious items
Determine if the search plan needs modification
Review boundaries
Take detection equipment (audible response on)
Establish contamination control area (if necessary)

24. Broad Area Building Searches
Search buildings first
Visit all floors
Search rooms with the following items first
Radiation-related signs
Attic or basement areas
Suspicious looking items
Garbage containers
Industrial shop areas
Floor drains
Sewer lines

25. Broad Area Field Searches
Search after buildings
Pay particular attention to:
Radiation-related signs
Ditches, sheds or trailers
Suspicious looking items
Garbage containers
Above-ground tanks
Septic or sewer areas
Earthen mounds
Underground tanks

26. Source Localization and Identification
Localize the source
Use the appropriate range radiation detection instrument to approach the source
Move in slowly
May need the use of tools such as a shovel to find the source (use care not to damage the source)

27. Source Localization and Identification
Control access to the area and post trefoil sign as appropriate
Assess the need for shielding
Get accurate dose rate measurements at 1 meter if dose rates allow
Identify the radionuclide
Estimate the activity of the source
Evaluate the best follow up actions

28. Possible Actions as a Result of the Search
No sources found…
If expected to find source:
Revise search plan
Expand search areas
Perform further administrative searches
If didn’t expect to find a source:
Document the area searched
Sources found…
Prepare sources for transfer to
authorized recipient or secure in place
If search was to verify an inventory, document the source location

29. When do you stop searching?
Factors to consider:
Whether or not there are any further useful clues or leads to be investigated
Category of the source, if known
Likely consequences of the source being found by a member of the public
Half-life, activity and time since the loss of source
Likelihood of the source being in a location accessible to the public
Need for resources to be used for other work
Public and political pressure and level of concern

30. Document the Search Record the following data for found sources:
The unique identification of the source (typically the manufacturer, model number and serial number of the source and the device)
The location of the source (installed location or location of authorized use)
The isotope and activity of each source. For all sources, record radiation measurement data (dose rate and spectrum/isotope identification)
The status of the source, i.e., “in use,” “disused,” “waste,” “missing”

31. Document the Search Record: Copy all survey documentation
Actions taken to secure the source
Disposition of the source
Copy all survey documentation
Write a discussion of the problems encountered during the search
Include digital photographs of the site, buildings, source or device, and important features that are correlated to the search maps

32. Summary
Planning, preparation, and procedures are important components in all types of physical searches
Key decisions involve:
What type of search to make?
Where to search?
What resources are needed and available?
What to do with any found sources?
When to stop?