Why does this script not create and explosion?

function NuclearSequence()
    game.Lighting.Ambient = Color3.new(190,109,0)
    game.Lighting.OutdoorAmbient = Color3.new(190,109,0)
    game.Lighting.Brightness = 150
    game.Lighting.FogEnd = 5
    k = Instance.new("Explosion", game.Workspace)
    k.ExplosionType = "NoCraters"
    k.BlastRadius = Vector3.new250000000000000000000
    k.BlastPressure = 2500
    k.Position = Vector3.new(0,13.6,0)
    for i=1,149 do
        game.Lighting.Brightness = game.Lighting.Brightness - 1
        game.Lighting.FogEnd = game.Lighting.FogEnd + 670
        wait(.5)
    end
    game.Lighting.Ambient = Color3.new(117,117,117)
    game.Lighting.OutdoorAmbient = Color3.new(128,128,128)
end

It creates no explosion, everything else works correctly.