Chromium-51 (Cr-51)

DOE-HDBK-1106-97

CHROMIUM-51 (Cr-51)

Chromium-51 is a gamma and an X-ray emitter. Cr-51 is readily detected with a thin-window G-

M probe. Liquid scintillation counting is also used.

1. Maximum energy: 0.32 MeV gamma ray (9.8%), a very low energy (0.005 MeV) X-

ray (22 %), and 0.004 MeV (66.9%) auger electron.

2. IAEA toxicity classification: Medium-low.

3. Physical half-life: 27.7 days.

4. Effective biological half-life: 27 days.

5. Critical organ: Lower large intestine and lungs.

6. Personnel monitoring: Dosimeter, internal uptakes may be determined by urine or fecal

sampling.

7. ALI:

20 mCi (7 x 108 Bq) by inhalation, yearly clearance.

20 mCi (7 x 108 Bq) by ingestion.

8. Shielding: - 3.2 mm of lead is the first half value layer (thickness of lead that will

reduce the dose rate by one-half).

9. Special Considerations:

Use thin-end window G-M or solid scintillation detectors or liquid scintillation

counting.