I modified your design a little. Far more output and just a little more strain on cooling. I did replace the plates with LZH-condensators, the output grows substantually from replacing them with thick neutron reflectors! Here:
http://two66.com/reactorplanner.html?21p7i4slsbluw9qf05kufpr7pac9ip0cez8lrcazwvazz20ng5i7rhwda3hyy6adjo1hmku178kf6rk