  \Xe{136} is used as the target medium for many experiments searching for
\bbnonu. Despite underground operation, cosmic muons that reach the laboratory
can produce spallation neutrons causing activation of detector materials. A
potential background that is difficult to veto using muon tagging comes in the
form of \Xe{137} created by the capture of neutrons on \Xe{136}. This isotope
decays via beta decay with a half-life of 3.8 minutes and a \Qb\ of $\sim$4.16
MeV. This work proposes and explores the concept of adding a small percentage
of \He{3} to xenon as a means to capture thermal neutrons and reduce the number
of activations in the detector volume. When using this technique we find the
contamination from \Xe{137} activation can be reduced to negligible levels in
tonne and multi-tonne scale high pressure gas xenon neutrinoless double beta
decay experiments running at any depth in an underground laboratory.
