Position-dependent delayed-neutron fractions for IQS calculations and application to PHWR kinetics calculations
- Resource Type
- Authors
- Qingjie Liu; Eleodor Nichita
- Source
- Nuclear Engineering and Design. 339:150-158
- Subject
- Nuclear and High Energy Physics
Work (thermodynamics)
Materials science
Astrophysics::High Energy Astrophysical Phenomena
020209 energy
Mechanical Engineering
Fraction (chemistry)
02 engineering and technology
Mechanics
01 natural sciences
010305 fluids & plasmas
Amplitude
Nuclear Energy and Engineering
Neutron flux
0103 physical sciences
0202 electrical engineering, electronic engineering, information engineering
General Materials Science
Spatial dependence
Diffusion (business)
Nuclear Experiment
Safety, Risk, Reliability and Quality
Waste Management and Disposal
Delayed neutron
Burnup
- Language
- ISSN
- 0029-5493
The core of a Pressurized Heavy-Water Reactor (PHWR) contains fuel bundles with burnups varying between zero and the discharge burnup. Because the delayed-neutron fraction varies (decreases) with burnup, the spatial variation of the fuel burnup causes the delayed-neutron fraction to also depend on position. High-fidelity kinetics calculations need to account for such spatial dependence of the delayed-neutron fraction. This work documents the implementation of the capability to model position-dependent delayed-neutron fractions in the multi-group diffusion code DONJON which performs kinetics calculations using the Improved Quasi-Static (IQS) method. Consistent with the IQS method, the effect of the spatial variation of the delayed-neutron fraction is accounted for both in the overall effective delayed neutron fraction and in the spatial dependence of the delayed-neutron source. Consequently, both the amplitude and the shape of the neutron flux are impacted by the position-dependence of the delayed-neutron fraction. The functionality of the newly-implemented capability is tested for a stylized coolant-voiding transient in a PHWR core and differences in reactor power and core neutron flux shape are shown to exist between the results of calculations that use position-dependent delayed-neutron fractions and those that only use spatially uniform ones.