N-16 Levels

[JSBland@aol.com]

I have been asked a question related to N-16 production at a PWR and any 
dependency on core life.  Does N-16 production increase with core life?  I 
have examined the difference in the neutron energy spectrum between U-235 
fission and Pu-239 fission.  With a 9.6 MeV neutron energy threshold for the 
O-16(n,p)N-16 reaction, it appears that the higher neutron energy spectrum 
from Pu-239 should yield a higher N-16 production rate later in core life. 
But, I don't recall (nor can I find) any data to support this hypothesized 
increase.  I have also examined the issue of prompt gammas from fission that 
would yield high energy gammas that could be mistaken for N-16, especially 
while looking at a wide energy band for identification purposes (3 to 7.5 
MeV, over which I have no control).  In this case, the U-235 spectrum yields 
more gammas in this energy band than does the Pu-239 spectrum.  Unfortunately 
for me, this is not a research project, just a "can you help explain this,"
 so I have no resources available for measurements.   Any help or suggestions 
are appreciated.
J. Stewart Bland
(jsbland@aol.com)
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