Chromium-51 (Cr-51)

DOE-HDBK-1106-97

Instructor's Notes

CHROMIUM-51 (Cr-51)

Chromium-51 is a gamma and a 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 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.