Reactivepowerproblemplaysvitalroleinsecureandeconomicoperationsofpowersystem.AvarietyofmethodslikeNewton’smethod,interiorpointmethod;successivequadraticprogrammingmethod[1-5]havebeenalreadyusedtosolvetheoptimalreactivepowerproblem.Howeverhandlingtheconstraintsisverymuchdifficultbyconventionalmethods.ThenEvolutionarytechniquessuchasgravitationalsearch,particleswarmoptimization,symbioticorganismsearchalgorithm[6-13]areappliedtosolvethereactivepowerproblem.ThispaperproposesSpontaneousProcessAlgorithm(SPA)aphysics-basedalgorithmwhichhasbeeninspiredbynuclearreactiontosolveoptimalreactivepowerproblem.ProcessofNuclearfissionandfusionareutilizedtoformulatethealgorithm[14-17].InordertoexplorethenearbyareapositionsandalsotocontrolthecapabilityofexplorationandexploitationβdecaywillbeemulatedbyGaussianwalk.GettingtrappedinLocaloptimalsolutionisavoidedbyapplyingtheLevyflight.Inexplorationspaceeachsolutionsymbolizesanucleuswhichpossessmassnumber,charge,location,potential&kineticenergy.Duetothetwodissimilararbitrarynucleitheheatedneutronswillbeengenderedthroughnuclearfusion.Inionizationphase,allnucleusesarecategorizedthroughfitnessvalues.Thei-thnucleuscanbedescribedbyprobabilityvalueswhichcompletelyabidebyuniformdistribution.Superiorityofexplorationisenhancedbyapplyingdifferentplansenthusedbyvariantsofdissimilaroperatorswhichusedtoimitatethecollisionandfusion.ProposedSpontaneousProcessAlgorithm(SPA)hasbeentestedinstandardIEEE14,30,57,118,300bustestsystemsandsimulationresultsshowtheprojectedalgorithmreducedtherealpowerlosscomprehensively.