Stanley, the gamma radioactivity from U232 decay chain is only an issue if someone wants to isolate the uranium bred in the reactor and run away with it - then there is additional protection in the Th/U cycle which is not necessarily present in U235 or U238/Pu239 based fuels.
As long as the uranium stays in the reactor (as it should), this activity is insignificant compared to all the "regular" gammas associated with the fission process and FP decays. Therefore there are no additional measures or costs due to U232 activity.
Now all MSRs likely need to be operated in a hotcell in a double containment to provide for enough independent barriers to fission products. I would expect however that the cost of that would be significantly smaller than the containment costs of water cooled reactors, as there is no high pressure steam or other pressure/chemical driver to take the core out in the MSR, so the containment can be much smaller and close fitting - it just needs to be leak-tight and protect against external events, it does need to hold enormous pressures from the inside.