Neutronics Design And Analysis Of Burnable Poisons For Long-Life Commercial PWR

Core life is a key indicator of reactor performance.At present,all commercial pressurized water reactors use burnable poisons to extend the core life,improve fuel utilization,and reduce fuel cycle costs.The key to burnable poison optimal design is better to match the consumption of burnable poisons and fuel burnup.The consumption of the ideal burnable poison and fuel consumption should be optimally matched in time and space relationships.Therefore,the ideal burnable poison needs to have excellent neutronic performance and good power distribution control capabilities.This article aims to achieve long-life commercial pressurized water reactors,uses the deterministic assembly calculation program DRAGON5,and takes the typical fuel assembly AFA-3G as the research object,Carried out burnable poison evaluation method,burnable poison absorber materials and loading patterns research.The research mainly includes:First,the calculation of the fuel consumption of gadolinium-containing fuel assemblies with strong self-shielding effect is verified based on the calculation result of Monte Carlo.Then studied the evaluation methods of burnable poisons,the guiding principles and specific standards for the selection of burnable poisons were put forward,and the materials of burnable poison absorbers were preliminary screening.Finally,the advanced polymer burnable poisons(PACS),single isotope burnable poisons,particle type burnable poisons,and combinational burnable poisons were studied in neutronics.The neutronics properties of the above burnable poisons were analyzed in terms of reactivity control and power distribution flattening.The study shows that DRAGON5 uses a two-level calculation scheme to achieve more efficient and accurate burnup calculations for gadolinium-containing fuel assemblies,meeting the design requirements of long-life commercial pressurized water reactors.Advanced polymer burnable poisons can eliminate the end-of-life reactivity penalty caused by the water displacement effect of other separated boron-containing burnable poison,extends the cycle length available for burnable poison assemblies.with greater negative reactivity introduced at the beginning of life and less reactivity swing during core life.Single isotopes as burnable poisons reduce the initial loading of poisons,and the residual amount of burnup poison in the assemblies at the end of life is significantly reduced,with a greater range of regulation of the self-shielding effect,which is conducive to a smoother reactivity release.particle type dispersion burnable poisons can adjust the self-shielding effect of burnable poisons by changing the particle radius,which greatly improves the flexibility of reactivity control.Under specific operating conditions,the boron-containing BISO particles achieve a better match between reactivity release and burnup poison consumption in the range of up to 40GWd/t U with low soluble boron concentration in the coolant,and there is basically no reactivity penalty at the end of life.Replacing a single burnable poison with combinational burnable poisons can effectively compensate for excess reactivity at the beginning of life while improving reactivity control and power distribution control,and adjusting the proportion of burnable poisons in the combination can change the burnup characteristics of the combinational burnable poisons.In summary,the research results show that advanced polymer burnable poisons,single isotope burnable poisons,particle-dispersed burnable poisons,and combinational burnable poison have good neutronic performance,meeting the burnable poisons requirements of long-life commercial pressurized water reactors and can be used as candidate burnable poisons for long-life commercial pressurized water reactors where particle-type dispersion burnable poisons provide a reference for achieving low-boron operation of long-life commercial pressurized water.