From What-If folks: What if I took a swim in a typical spent nuclear fuel pool? http://what-if.xkcd.com/29/
...."Assuming you’re a reasonably good swimmer, you could probably
survive treading water anywhere from 10 to 40 hours. At that point, you
would black out from fatigue and drown. This is also true for a pool
without nuclear fuel in the bottom."
Welcome to the Future of Neutron Scattering in Canada
a grassroots, nonpartisan movement of ordinary Canadians
that emerged in response to the lack of commitment by federal government(s) to build a new research reactor in Canada for nearly 2 decades.