Re: Neutron Quality Factor

[kmq@cosmail1.ctd.ornl.gov (Kim McMahan)]

At 02:36 PM 4/11/96 -0500, you wrote:
>>I'm inquiring about the neutron QF decrease above 1 MeV. Can someone provide
>>the basis for this?  I have yet to find/hear a good accounting.
>
>Scott Schwahn's reply mentioned the variation of cross sections with energy.
>In addition, the average kinetic energy of the recoil proton varies,
>high energy neutrons generally produce higher energy recoil protons,
>which have a lower LET, and so a smaller QF.
>i.e. the neutron QF depends (in part) on the QF of the recoil proton.
>
>Stay safe, mike (mcnaught@LANL.GOV)
>
>

Maybe an additional fact will help draw this together. The QF is a function
of  LET, which is defined for **charged particles**.  QF does increase
(stepwise, since it's a consensus thing) with increasing LET. But the
distribution of recoil protons, recoil atoms, alpha particles, etc. varies
with neutron energy, so average quality factors, that take into account the
various interaction probablilties at a given neutron energy, have been
calculated and are what you find in the regulations.

Kim McMahan
Office of Radiation Protection
Oak Ridge National Laboratory
Phone:  (423) 576-1566
e-mail: mcmahankl@ornl.gov