Pressurized water reactors are more susceptible to embrittlement than boiling water reactors. This is due to PWRs sustaining more neutron impacts. To counteract this, many PWRs have a specific core design that reduces the number of neutrons hitting the vessel wall. Moreover, PWR designs must be especially mindful of embrittlement because of pressurized thermal shock, an accident scenario that occurs when cold water enters a pressurized reactor vessel, introducing large thermal stress. This thermal stress may cause fracture if the reactor vessel is sufficiently brittle.