RE: Activation of concrete

["Tupin, Edward A. 301-827-1230 Fax 594-4760" <EAT@FDADR.CDRH.FDA.GOV>]

Eu-154 is a thermal neutron capture product from (stable, 52% of 
naturally occuring Eu) Eu-153.  The capture cross section is about 1400 
barns. 43 MeV is enough energy to produce photo neutons from the 
accelerator.  With a half life of 16 years, it is not surprising that 
the Eu-154 is still around.

You may actually have both Eu152, as Les Slaback noted, and Eu154.  The 
decay emmissions are similar, as are the half lives and modes of 
production.

Eu-152 is the thermal neutron capture product of (stable, 48% of 
naturally occuring Eu) Eu-151.  The capture cross section is about 5000 
barns.     

Ed Tupin
RSO, Center for Devices and Radiological Health
EAT@fdadr.cdrh.fda.gov
(301) 827-1230
Fax:  (301) 594-4760