Appendix IV: Boston University / Boston Medical Center Contamination Action Limits for Release
Updated May 2020
Appendix IV: Boston University / Boston Medical Center Contamination Action Limits for Release
Surface Contamination Levels in Restricted Areas (dpm/100 cm2)
| Area, clothing | Restricted areas, protective clothing used only in restricted areas |
| alpha emitters | 200 |
| P-32, Co-58, Fe-59, Co-60, Se-75, Sr-85, Y-90, In-111, I-123, I-125, I-131, Sm-153, Yb-169, Lu-177, Au-198 | 2000 |
| Cr-51, Co-57, Ga-67, Tc-99m, Hg-197, Tl-201 | 20000 |
Surface Contamination Levels in Unrestricted Areas (dpm/100 cm2)
| Nuclide* | Average†, ‡, § | Maximum†, ║, § | Removable†, ¶, § |
| I-123, I-125, I-129, Ra-223, Ra-224, Ra-226 | 100 | 300 | 20 |
| I-126, I-131, I-133, Sr-90 | 1000 | 3000 | 200 |
| Beta-gamma emitters (nuclides with decay modes other than alpha emission or spontaneous fission) except those noted above. | 5000 | 15000 | 1000 |
*Where surface contamination by multiple nuclides exists, the limits established for each nuclide should apply independently.
†As used in this table, dpm means the rate of emission by radioactive material, as determined by correcting the counts per minute observed by an appropriate detector for background, efficiency, and geometric factors associated with the instrumentation.
‡Measurements of average contaminants should not be averaged over more than 1 square meter. For objects of less surface area, the average should be derived for each such object.
§The average and maximum radiation levels associated with surface contamination resulting from beta-gamma emitters should not exceed 0.2 millirad/h at 1 cm and 1.0 millirad/h at 1 centimeter, respectively, measured through not more than 7 milligram/cm2 of total absorber.
║The maximum contamination level applies to an area of not more than 100 cm2.
¶The amount of removable radioactive material per 100 cm2 of surface area should be determined by swiping that area with filter or soft absorbent paper, applying moderate pressure, and assessing the amount of radioactive material on the wipe with an appropriate instrument of known efficiency. When removable contamination on objects of less surface area is determined, the pertinent levels should be reduced proportionally, and the entire surface should be wiped.
Action if > Release Limit
| Room | Equipment |
| Hold for decay* | Hold for decay |
| Clean | Hold for decay** |
| Clean | Hold for decay |
* CAUTION – The decision to prevent access to a room or area while waiting for alpha emitting isotopes to decay must be undertaken very carefully. Rooms or areas to which access is denied for greater than 8 working hours due to radioactive contamination will trigger an immediate report to the state Radiation Control Program. Alternate control strategies that will not trigger reporting requirements should be considered such as allowing access only by approved authorized users and implementing survey in and out protocols.
** Equipment such as refrigerators, centrifuges, etc., may be held for decay provided the half-life of the contaminating isotope does not require holding the item for extended periods. Depending on storage capability, equipment and items should not be held for more than 6 months for practicality purposes unless approved by the Executive Director of EHS.
Most Commonly Used Radioisotopes at BU/BMC
| Radioisotope | Half-Life in hours | Energy |
| F-18 | 1.8 | 633.2 keV (Positron)0.511 MeV x2 (gamma) |
| Tc-99m | 6.0 | 140.5 keV (gamma) |
| I-123 | 13.2 | 158.9 keV (gamma) |
| Tl-201 | 72 | 167 keV (gamma) |
| Xe-133 | 124.8 | 81 keV (gamma) |
| P-32 | 343.2 (14.3 days) | 1710 keV (Beta Max) |
| P-33 | 607.2 (25.3 days) | 249 keV (Beta Max) |
| Cr-51 | 664.8 (27.7 days) | 320 keV (gamma) |
| I-125 | 1430.4 (59.6 days) | 27 keV (xray)35 keV (gamma) |
| S-35 | 2097.6 (87.4 days) | 166.7 keV (Beta Max) |
| Fe-55 | 23827.2 (2.72 years) | <10 kev=”” x-ray=”” auger=”” td=””> |
| H-3 | 108186 (12.35 years) | 18.6 keV (Beta Max) |
| Sr-90 | 249660 ( 28.5 years) | 546.2 keV (Beta Max) |
| C-14 | 50194800 (5730 years) | 156.5 keV (Beta Max) |
*Half-life and Energy from NCRP Report No. 58