For the IRF530 the drain-source breakdown voltage is something over 100V, so expect that.
An ideal inductor will do something non-sensical like produce infinite voltage and/or or self resonate at a gamma-ray frequency.
Real indictorsinductors are lossy and self resonate at lower frequencies so you will tend to see voltages in the general range of "too much" and self resonance in the range of "annoy radio users"