Physical Searches for Orphan Sources

1. Physical SearchesforOrphan 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 pointsto 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 • Routine: • 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 • 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: • Search procedures • Source securing, storage and transfer procedures • Health and safety precautions • Preparation • Equipment and material procurement • Transfer sample plan onto searchmaps 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/materialsfor 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 backgroundmeasurement 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 carenot 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: • 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 ordevice, 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?