The thermal response of the first wall and blanket due to power/cooling mismatch in the absence of operator action is examined. The analyses of coolant and power transients are carried out on six reference blanket designs representing a broad range of fusion first wall and blanket technology. It is concluded that the requirement of plant protection will impose sufficiently stringent peak neutron wall loading limits to avoid a serious threat to the public. It is found that for the D–T designs, the operating wall loading may have to be limited to 3–8 MW/m2 for passive plant protection, depending on the plant design.