Orphan Source Search Training Actions After Finding an

Orphan Source Search Training Actions After Finding an Orphan Radioactive Source – Source Recovery

Actions After Finding an Orphan Radioactive Source - Introduction • There are four distinct steps that must be implemented after finding an orphan radioactive source. These steps are: – – Orphan source identification and characterization Packaging and transport Conditioning Safe and secure storage • This presentation addresses the first step, identification and characterization Actions After Finding an Orphan Radioactive Source – Source Recovery 2

Overview • • Orphan source identification and characterization Initial actions – dose assessment/reconstruction Source/device information Source characterization Gamma ray constants and shielding factors Radiography example Sample source transfer form Actions After Finding an Orphan Radioactive Source – Source Recovery 3

Initial Actions – Radiological Safety • Control access in the area around the source/device – e. g. rope off at an acceptably low dose rate (0. 1 m. Sv h-1), as appropriate. • Observe the source from a distance (e. g. using binoculars, as appropriate) • Approach the source slowly using a dose-rate meter, as appropriate. • Ensure dose rates are acceptable for subsequent actions in all directions around the device/source - in case there is a beam Actions After Finding an Orphan Radioactive Source – Source Recovery 4

Initial Actions – Radiological Safety <1 Sv/h 520 Sv/h Actions After Finding an Orphan Radioactive Source – Source Recovery 5

Initial Actions – Radiological Safety Dose assessment (reconstruction) Actions After Finding an Orphan Radioactive Source – Source Recovery 6

Initial Actions – Radiological Safety Dose assessment (reconstruction) Actions After Finding an Orphan Radioactive Source – Source Recovery 7

Initial Actions – Radiological Safety • Measure the dose rate near the device/source (at contact and at 1 meter), if safe. • Swipe the device/source for leakage or contamination using long-handled tongs. Monitor swipe elsewhere, away from the source • Check for damage (if safe): Damaged portable gauge – Shield intact? – shutter open or closed? Actions After Finding an Orphan Radioactive Source – Source Recovery 8

Device/Source Information Requirements Gather as much information as you can, in the field, about – Radionuclide – Activity – Dose rates – Contamination levels Device data plates, Markings on a shipping package, Shipping paper work. All are helpful. Actions After Finding an Orphan Radioactive Source – Source Recovery 9

Initial Actions – Source Identification • • Record data from any label present, if legible Take pictures of label plate and source Actions After Finding an Orphan Radioactive Source – Source Recovery 10

Initial Actions – Source Identification • • Identify radionuclide using a hand-held spectrometer Record the results and save the spectrum Actions After Finding an Orphan Radioactive Source – Source Recovery 11

Initial Actions – Source Identification • Attempt to specifically identify the source/device or failing this, to identify the type of source using: – The observed and measured data – Information provided in the IAEA Nuclear Security Series no. 5 – Information from the administrative search – Available data regarding missing sources – Other references such as the IAEA International Catalogue of Sealed Radioactive Sources (ICSRS) Actions After Finding an Orphan Radioactive Source – Source Recovery 12

Source Characterization • Determine the source activity from: – data on the label and a decay correction, or if no information available, – dose rate at a known, safe distance and knowledge of the isotope identified (for beta/gamma sources) Actions After Finding an Orphan Radioactive Source – Source Recovery 13

Source Characterization Γ. A D= r 2 A= Actions After Finding an Orphan Radioactive Source – Source Recovery D. r 2 Γ 14

Source Characterization • • Use inverse square law and specific gamma ray constants Account for any shielding present • Dose rate changes with distance • D 2 (r 22) = D 1 (r 12) Inverse Square Law Use of Measured Data • • • D 1 = Measured dose rate at distance r 1 D 2 = Dose rate at distance of interest r 2 D 3 = Dose rate at distance of interest r 3 15

Some Specific Gamma Ray Constants Nuclide (mrem/hr)/m. Ci @ 1 m (μSv/hr)/MBq @ 1 m 60 Co 1. 29 0. 306 137 Cs 0. 32 0. 076 192 Ir 0. 48 0. 113 226 Ra* 0. 73 0. 173 * = in equilibrium with daughters Actions After Finding an Orphan Radioactive Source – Source Recovery 16

Some Shielding Factors Nuclide 60 Co 137 Cs 192 Ir 226 Ra HVL or TVL Concrete (2. 5 g/cm 3) Lead (11. 3 g/cm 3) HVL 6. 2 cm 1. 2 cm TVL 21. 8 cm 4. 5 cm HVL 4. 8 cm 0. 7 cm TVL 17. 5 cm 2. 2 cm HVL 4. 3 cm 0. 6 cm TVL 15. 2 cm 1. 6 cm HVL 6. 9 cm 1. 7 cm TVL 24. 0 cm 4. 5 cm Numbers taken from IAEA Safety Series No. 47 Actions After Finding an Orphan Radioactive Source – Source Recovery 17

Example - Radiography • A source identified as 60 Co for industrial radiography, in its shielded position is measured to have a dose rate of 50 μSv/h at one meter • The camera data plate indicates an activity of 100 Ci five yrs ago. • The half life of Co-60 is 5. 26 yr. Therefore one half of the activity has decayed and the camera contains about 50 Ci of Co-60. Actions After Finding an Orphan Radioactive Source – Source Recovery 18

Example (cont. ) • A source identified as 60 Co for industrial radiography, without any data, in its shielded position, is measured to have a dose rate of 50 μSv/h at one meter • The camera lead shield seems to be about 20 cm thick. • 20 cm is about 4 tenth value layers (TVL), so the dose rate from an unshielded source would be about 10, 000 times greater i. e. 500 m. Sv/h at one meter Actions After Finding an Orphan Radioactive Source – Source Recovery 19

Example (cont. ) D x. r 2 A= Γ • Hence the activity of the source is about: 500 (m. Sv/h)/3. 06 x 10 -4 MBq/(m. Sv/h) 1. 63 x 106 MBq or 1. 63 TBq • This is consistent with a 60 Co industrial radiography source as given in App I, Table 2 of RS-G-1. 9 (Categorization of Radioactive Sources) • It would be a Category 2 source Actions After Finding an Orphan Radioactive Source – Source Recovery 20

Next Actions • Once the initial actions have been completed – the device/source will usually need to be packaged for transport – paperwork, labels, and marking must be prepared – transport it to a safe and secure location – condition the source/device, as needed – store it in a safe and secure manner awaiting a decision on final disposition. Actions After Finding an Orphan Radioactive Source – Source Recovery 21

Example of a source transfer form Actions After Finding an Orphan Radioactive Source – Source Recovery 22

Summary • Why is it important that the radiological environment of the orphan source be fully characterized? • What information should be used to characterize the source? • Why is the source/device transfer form important? Actions After Finding an Orphan Radioactive Source – Source Recovery 23

Thank you!