That seems likely - my guess is you'll need sufficiently efficient energy to power electromagnetic shielding. Although an old Submarine-style nuclear fission reactor might be just fine for that as well, and you won't have to worry about just venting spent fuel rods into vacuum (in a nuclear pulse type spaceship that bit of radiation is going to be the least of your worries...).
It seems likely to me that mastering fusion will be a pre-requisite for interstellar travel. But you're right, that's probably the weakest part of my argument. So maybe there will be a market for rare shipping rare elements across interstellar distances.