51 Radioactive Materials Safety Manual 51Cr CHROMIUM-51 Half - Life Physical Biological Effective 27.7 days 616 days 26.6 days Radiation Emitted Type Energy (max) Gamma 320 keV (9.8%) X-Rays 5 keV (22%) External Hazard 1 meter 1 cm Dose rate from a 1 mCi (37 MBq) point source: 16 µrad/hr (0.16 µGy/hr) 160 mrad/hr (1.6 mGy/hr) Internal Hazard Effective Committed Dose Ingestion Inhalation Equivalent per Unit Intake: 0.15 mrem/µCi (3.98 x 10-11 Sv/Bq) 0 .11 mrem/µCi (2.95 x 10-11 Sv/Bq) Annual Limit on Intake: (ALI)* 40 mCi 50 mCi *ALIs expressed are from Appendix B, Table 1 – Iowa Administrative Code 641.40 (136C). Special Considerations • None Radiation Safety Practices • Dosimetry – Whole body badges may be required when working with quantities greater than 5 mCi (185 MBq). • Bioassay – Required for individuals involved in spills or other incidents where significant uptake is suspected. • Shielding – 7.8 mm lead provides 95% attenuation; lead HVL is 1.7 mm. • Surveys – Scintillation meter surveys; wipes analyzed in an LSC or gamma counter.
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