December 3, 2007
University of Windsor Radiation Safety Bulletin Contamination Monitoring
The University of Windsor’s Radiation Safety Polices and Canadian Nuclear Safety Commission’s (CNSC) consolidated licence stipulates that all licensed radioisotope laboratories develop and utilize a laboratory specific radioactivity contamination monitoring program. As such, all radioisotope facilities must be monitored for contamination and detailed records maintained supporting the contamination detection program. Methods of Measurement: Direct: Measurements are taken using a portable radiation detection instrument to detect both fixed and removable contamination. Steps: 1. Monitor the locations listed on your plan by slowly moving the detector face toward the surface being monitoring. 2. If contamination is detected, stop and obtain a measurement. Record the reading (Bq). 3. Determine if the reading is above the licence criteria. If so, clean the area. 4. Re‐monitor the location for each cleaned area and record the final measurement (Bq) after decontamination. Indirect: Measurements are indirectly taken by measuring the amount of radiation which is transferred to a disposable wipe. Steps: 1. Using uniform and constant pressure, wipe approximately 100cm2 of each area on your plan with a filter paper, wipe, or cotton swab which is lightly moistened with alcohol or water. 2. Count the wipes using a liquid scintillation counter or using a contamination monitor if the wipe is equal or less than the area of the detector. 3. Determine if the readings observed are above the licence criteria. If so, clean the area. 4. Re‐monitor the location for each cleaned area and record the final measurement (Bq) after decontamination. University of Windsor Radiation Safety Bulletin – Contamination Monitoring University of Windsor Radiation Safety Bulletin Contamination Monitoring
Location, Location, Location: The locations which are to be monitored must be numbered on a plan of the radioisotope work area. These surfaces should include working surfaces (i.e. benches, counter tops, and fume hoods) along with non‐working surfaces (i.e. instruments, door handles, and phones). In addition, a few random locations should also be included. Frequency: All radioisotope laboratories actively using radioactive materials must be monitored at least on a weekly basis to detect surface contamination. If no radioisotopes have been used since the previous survey, permit holders are not required to conduct contamination monitoring until the next usage. However, it should be recorded in the “Radioisotope Inventory Record” log book that no radioactive work has been conducted. Decontamination: Any area that is found to have non‐fixed contamination exceeding the regulatory criteria must be cleaned and re‐monitored. Please refer to your University of Windsor Radioisotope Permit for more information or visit our website (www.uwindsor.ca/ccc). Radionuclide December 3, 2007
C‐14 H‐3 P‐32 S‐35 EQ (MBq) Wipes Controlled area (Bq/cm2) Wipes Public area (Bq/cm2) 100 300 30 1000 300 30 0.01 300 30 100 300 30 Please see permit for specific information Monitoring Records: The results of all wipe tests must be kept within the log‐book for up‐to three years. The “Radioisotope Inventory Record” should be kept within the licensed area and available for inspection by either the RSO or CNSC Inspectors. Please see appendix for an example of a monitoring record sheet. University of Windsor Radiation Safety Bulletin – Contamination Monitoring University of Windsor Radiation Safety Bulletin Contamination Monitoring
Calculations: Formula
Removable activity (Bq/cm2):
N ‐ NB / E x 60 x A x (F)
Description
Total count rate in counts per minute (CPM) measured directly or on the wipe
Normal background count rate (CPM) from the survey insturment or ont the blank
Instrument efficiency factor (%) for the radioisotope being measured
Sec/min
Area wiped (not to exceed 100 cm2) or the area of the detector
Collection factor of the wipe (assume 10%)
Value
N
NB
E
60
A
F
Detector Efficiencies:
Perkin‐Elmer Tri‐Carb© 2900 liquid scintillation analyzer Isotope
Efficiency
C‐14
95%
H‐3
58%
P‐32
98%
S‐35
95%
Example Calculation: Formula
Removable activity N ‐ NB / E x 60 x A x (F)
(Bq/cm2):
N
NB
E
December 3, 2007
60
A
F
Liquid Scintiallation Calculations
157
90
98%
Isotope: P32
60
100
10%
Removable activity (Bq/cm2):
0.113945578 University of Windsor Radiation Safety Bulletin – Contamination Monitoring Time
Surveyor's Name
Isotope Used
Work Area
Survey Type
Personal
University of Windsor Radiation Safety Program ‐ Laboratory Survey Log
Date
Results (Bq/cm2)
* For more information, please refer to the University of Windsor's Radiation Safety Program website (www.uwindsor.ca/radiation)
Survey Meter User: Mfg., Model, Serial No, & Probe Type