From your pix, you have a square taper crank with a BB that has splined retainers for the bearings, which have been almost universal over the past 20 yrs or so
for BB. The sq taper BB axle is less common as most riders on this forum use newer BB axles which are larger in diameter, hollow and have splined ends.
Sq taper BB are readily available, I agree with alcphil, your axle is unlikely to break, its most susceptible part to breakage is the axle-crank retention bolt if
you overtighten it.