Research On The Small Pressurized Water Reactor Using Accident Tolerant Fuel

The safety is the life of nuclear energy.Nuclear energy is one kind of clean and high-effective energy,which should be developed very well when the global climate changes.However,the insufficient safety constrains its development greatly.For post-Fukushima nuclear power plants,the nuclear industry and academic community think that the safety of nuclear energy should be improved to reduce the risk of fission production release.One of ways is utilizing accident-tolerant fuel(ATF).ATF is strongly desired in order to prevent radioactive release and eliminate the hydrogen explosion in the event of severe accidents to improve the safety of nuclear reactor.The other way is developing small reactor to reduce the probability of accident and even if the impact of accidents can be constrained in small range.However,the performance of ATF is related with the characteristic of fuel as well as the design optimizations when the accident happened.The Fully Ceramic Microencapsulated(FCM)fuel is one of the ATF.The dissertation is about the small pressurized water reactor(PWR)utilization FCM fuel.The FCM fuel will replace the traditional UO2 as fuel pellet in small PWR with 200 MWt.The safety analysis of small PWR utilization FCM fuel has been performed and some challenges have been solved.The heavy metal fuel loading would be much less than the traditional fuel at the same volumes.As a result,a naive use of FCM fuel can't achieve the acceptable cycle lengths for existing PWR designs.The volumes of fuel could not be improved as desired since the replacing fuel should keep the same dimension.Consequently,higher enrichment fuel(19.90 w/o enrichment)will be used to get long core life purpose.Soluble Boron Free operation concepts in small PWR will be introduced making reactivity control become difficult over the entire fuel cycle.In this paper,a neutronic study has been performed to apply burnable poison for excess reactivity management in a 200 MWt small PWR with soluble boron free concept.For the suppressing excess reactivity in small PWR utilizing FCM fuels,some burnable poisons were used,including adding Pu-238 to fuel kernel,utilization of Integral Fuel Burnable Absorber(IFBA)and Wet Annular Burnable Absorbers(WABA).The safety analysis of small PWR utilizing FCM fuels needs to be carried out to demonstrate the fuel performance.In the second part,the neutronic of reactor was studied by MCNP code to get the power distribution which would be sent to RELAP5 for analysis of steady state and transient state.A common RELAP5 application is used to simulate small break-loss of coolant accident(SB-LOCA)and large break-loss of coolant accident(LB-LOCA)but without emergency core coolant system(ECCS).The results show that the radioactive fission production can be contained in the fuel pellets even after the cladding failure since FCM provides multiple barriers to fission product release.The single batch fuel cycle could not have enough discharge burnup.But the multi-cycle can increase the fuel discharged burnup and reduce the excess reactivity.In the third part,the in-core fuel management for small PWR utilization FCM fuel has been performed.Three-batch and five-batch refueling strategies are simulated.The excess reactivity,cycle lengths,power peaking factor and discharged burnup are compared.Finally,the safety of small PWR utilization FCM could be enhanced partly.The inherent safety may come true if the reactor core is modified.The preliminary calculation shows that it is feasible for the decay heat can be removed only through heat radiation without ECCS since the lower power and lower power density.