Cobalt-57 (Co-57) - doe-hdbk-1106-97

DOE-HDBK-1106-97

Instructor's Notes

COBALT-57 (Co-57)

Cobalt-57 is an X-ray emitter. Most common means of detection is

with a thin-window G-M probe.

1. Maximum energy: X-ray radiation from 0.014 to 0.692

MeV (0.122 MeV emitted 85.5% of the time).

2. IAEA toxicity classification: Medium-low.

3. Physical half-life: 270.9 days.

4. Effective half-life (Teff): 9 days.

5. Critical organ: Lower large intestine.

6. Personnel monitoring: Dosimeter, uptakes may be

evaluated by whole body counting.

7. ALI:

0.7 mCi (3 x 107 Bq) by inhalation, yearly clearance.

4 mCi (2 x 108 Bq) by ingestion.

8. Shielding: 3.2 mm of lead is the half value layer.