Localisation of a channel instability in the Forsmark-1 boiling water reactor

A method IS elaborated and used for the locahsatlOn of a channel type Instablhty In a bOIlIng water reactor (BWR) by neutron nOIse techntques Locahsatton means determmmg the radial poslt1on(s) of the fuel channells) In whIch the Instablhty phenomenon occurs The problem and ItS solutIon show clear resemblance to that of the localIsation of vIbratmg absorbers In pres~unzed water reactors However, the spatial structure of the neutron nOise IS different for the two cases, thus different localIsation formulae need to be used. BesIdes, a new and very effective algonthm has been elaborated for the actual localisatIOn process The locahsatIOn method suggested was tested on simulated data with increasing &OphlStlCatlOn. and then on measurement data taken at the occurrence of a local mstablhty event III the SwedIsh BWR Forsmark-1 In early 1997 The results clearly demonstrate the apphcablhty and u~efulness of the method