Inthisworkwepresentthepredictionsofthe “ two-infallmodel ” concerningtheevolutionofD , ^ { 3 } Heand ^ { 4 } Heinthesolarvicinity , aswellastheirdistributionalongtheGalacticdisk.Ourresultsshowthat , whenadoptingdetailedyieldstakingintoaccounttheextra-mixingprocessinlowandintermediatemassstars , theproblemoftheoverproductionof ^ { 3 } Hebythechemicalevolutionmodelsissolved.Thepredicteddistributionof ^ { 3 } Healongthediskisalsoinagreementwiththeobservations.WealsopredictthedistributionsofD/H , D/OandD/Nalongthedisk , inparticularDabundancesclosetotheprimordialvaluearepredictedintheouterregionsoftheGalaxy.ThepredictedD/H , D/OandD/NabundancesinthelocalinterstellarmediumareinagreementwiththemeanvaluesobservedbytheFarUltravioletSpectroscopicExplorermission , althoughalargespreadintheDabundanceispresentinthedata.Finally , bymeansofourchemicalevolutionmodel , wecanconstraintheprimordialvalueofthedeuteriumabundance , andwefindavalueof ( D/H ) _ { p } \lesssim 4 \cdot 10 ^ { -5 } whichimplies \Omega _ { b } h ^ { 2 } \gtrsim 0.017 , inagreementwiththevaluesfromtheCosmicMicrowaveBackgroundradiationanalysis.Thisvalueinturnimpliesaprimordial ^ { 4 } HeabundanceY _ { p } \gtrsim 0.244 .