Chromium-51 Handling Precautions

Chromium-51 Handling Precautions
27.7 d
This document contains general information designed to provide a basic understanding of radiation
safety. While we believe the information to be accurate, regulatory requirements may change and
information contained herein is not tailored to individual needs. A radiation protection specialist
should be consulted for specific applications.
Physical data
Principal radiation emissions
Gamma: 0.320 MeV (9.8%)
X-ray: 0.005 MeV (22.3%)
Auger electron: 0.004 MeV (66.9%)
Unshielded exposure rate at 1 cm from a 1 mCi point
source: 0.18 R/h(2)
Unshielded exposure rate at 1 m from a 1 MBq point
source: 0.13 nC/kg/h
Half-value layer for lead shielding: 1.7 mm (0.067 in)(2)
Gamma emissions from 51Cr presents an external dose hazard. The retention of uptakes of 51Cr in the body is very
dependent on its chemical form(4). It may be assumed that
uptakes of 51Cr are retained in the transfer compartment
with a biological half-life of 0.5 days(4). 5% of the uptake
is then transferred to bone and retained with a biological
­half-life of 1000 days. 30% is directly excreted. 65% is distributed to other organs and tissues in the body; with 40%
of the uptake retained with a biological half-life of 6 days
and 25% retained with a biological half-life of 80 days(4).
Occupational limits(3)
Annual limit on intake: 40 mCi (1.5 GBq) for oral ingestion
and 20 mCi (740 MBq) for inhalation
Derived air concentration: 8 x 10-6 µCi/ml (300 kBq/m3)
Decay table
Physical half-life: 27.7 days(1).
To use the decay table, find the number of days in the top and
left hand columns of the chart, then find the corresponding
decay factor. To obtain a precalibration number, divide by
the decay factor. For a postcalibration number, multiply by
the decay factor. Visit to
use our online Radioactive Decay Calculator.
General handling precautions for Chromium-51
1.­Designate area for handling 51Cr and clearly label all containers.
Cr behind lead shielding.
3.­Wear extremity and whole body dosimeters while handling
mCi (37 MBq) quantities.
4.­­Use shielding to minimize exposure while handling
5. Use tools to indirectly handle unshielded sources and
potentially contaminated vessels.
6. Prohibit eating, drinking, smoking and mouth pipetting in
room where 51Cr is handled.
7. Use transfer pipets, spill trays and absorbent coverings to
confine contamination.
8.Handle 51Cr compounds that are potentially volatile or in
powder form in ventilated enclosures.
9.­­Sample exhausted effluent and room air by continuously
drawing a known volume through membrane filters.
10.­­Wear lab coat, wrist guards and disposable gloves for
secondary protection.
15. Establish surface contamination, air concentration and
urinalysis action levels below regulatory limits. Investigate
and correct any conditions that may cause these levels to
be exceeded.
16. On completing an operation, secure all 51Cr, remove and
dispose of protective clothing and coverings, monitor and
decontaminate self and surfaces, wash hands and monitor
them again.
Cr is slowly eliminated from the body. Whole body counting
provides a more sensitive method than urinalysis for determining
Cr body burdens. Whole body counting may be used occasionally to verify the urinalysis results.
1.­Kocher, David C., Radioactive Decay Data Tables,
Springfield: National Technical Information Service, 1981
12. Use end-window Geiger-Mueller detectors, NaI(Tl) detector
or liquid scintillation counter to detect 51Cr.
2.­Calculated with computer code “Gamma” utilizing decay
scheme data from Kocher(1) and mass attenuation coefficient for lead and mass energy absorption coefficients for
air from the Radiological Health Handbook, Washington:
Bureau of Radiological Health, 1970. The HVL reported
here is the initial HVL for narrow beam geometry.
13.­Submit urine samples for bioassay at least four hours after
handling 51Cr to indicate uptake by personnel.
3.­U.S. Nuclear Regulatory Commission. 10 CFR 20 Appendix B –
Standards for Protection Against Radiation, 1994.
14. Isolate waste in clearly labeled, shielded containers and
hold for decay.
4.­ICRP Publication 30, Part 2, Limits for Intakes of
Radionuclides by Workers. Pergamon Press, Oxford, 1980.
11.­­Maintain contamination and exposure control by regularly
monitoring and promptly decontaminating gloves and surfaces.
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Oct. 2011
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