I can tell you a commercial reactor plant has much more piping than say a A-4W aircraft carrier plant, and many times more than a S6G submarine reactor plant. When it comes to operation no one cares about much more than loop transient times, heatup and cooldown rates, and loop volumes.
Actual pipe lengths and exact layout also depend on the specific plant. I can tell you first hand that the 688 class submarines each are a little different, even while maintaining almost identical operational characteristics.