Spatial coupling for coupled code safety analysis of BWR design-basis accidents

• Analyses of nuclear reactor safety have increasingly requiredcoupling of full three dimensional neutron kinetics(NK) core models with system transient thermal-hydraulics(TH) codes. To produce results within a reasonable computingtime, the coupled codes use different spatial descriptionof the reactor core. The TH code uses few, typically 5 to20 TH channels which represent the core. The NK code usesexplicit node for each fuel assembly. Therefore, a spatialmapping of coarse grid TH and fine grid NK domain is necessary.However, improper mappings may result in loss ofvaluable information, thus causing inaccurate prediction ofsafety parameters. The purpose of this paper is to study thesensitivity of spatial coupling (channel refinement and spatialmapping) and develop recommendations for NK-THmapping in simulation of safety transients.The research methodology consists of spatial couplingconvergence study, as increasing number of TH channelsand different mapping approach the reference case. Thereference case consists of 700 TH channels, which givesone TH channel per one fuel assembly. The comparison ofresults has been done under steady-state and transientconditions. Obtained results and conclusions are presentedin this paper.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Energiteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Energy Engineering (hsv//eng)

Nyckelord

Boiling water reactors

Mapping

Nuclear propulsion

Nuclear reactors

Three dimensional

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