One fission reaction, of a U-235 nucleouse produces 2.4 Neutrons. In a pressurized water reactor, those uranium fuel rods are clad and sitting in water, giving off these neutrons. They are fast. The water slows them down, but does not absorb them and this generates heat. The inside of that reactor is protected by a stainless steel jacket several inches thick. That jacket also gets bombarded with these neutrons. The question is the following: Roughly what rate does that jacket get bombarded? [neutrons / time] How fast does that stainless steel jacket degrade, under such bombardment? [~20 years?] EPRI should have this info, but you need to be a member to get stuff off their website.