Indeed. In a thermal reactor, the energy of the neutrons is moderated down to the reactor operating temperature, and is typically a few tens of milli-electron volts (some tens of millions of times less energetic than when they were produced). These slow neutrons do impart a lot of energy when they are absorbed into a nucleus, but that's because of their binding energy into that nucleus. Due to nuclear shell effects, they add slightly more energy to nuclei with an odd number of neutrons, which is one reason why 235U can be fissioned with thermal neutrons and 238U cannot.
