RE: Ah, the good old days!
<0.5 rem per quarter (or 5 mSV) is in compliance with today's dose limit. ORNL was a competent American national lab with high standards even back in the 1960s. Another hollow argument from today's incompetent nuclear industry.
"Exposure of personnel to radiation has been held well below permissible limits: the maximum exposure of any individual in any quarter has been <0.5 rem." http://moltensalt.org/references/static/downloads/pdf/NAT_MS...
"The maximum annual dose allowed for radiation workers is 20 mSv/yr" https://www.world-nuclear.org/information-library/safety-and...
Ah, the good old days! 25-50% of the radioiodine from MSRE is completely unaccounted for. No one knows where it went. This is wholly unacceptable from a modern regulatory approach. It will have to be found.
http://moltensalt.org/references/static/downloads/pdf/ORNL-4...
> MSRE had salt-to-salt and salt-to-air heat exchangers made from hastelloy-N
Fair enough. It's generally in the salt-to-water heat exchanger where major maintenance concerns take place in a power reactor. Check out steam generator problems in PWRs and SFRs to see what I mean. You're right that the radiation will be low there if they use an intermediate salt. But the baseline maintenance problems come in at the steam generator in most plants. So MSRE avoided any problems there but any power MSR will have them like any other reactor. Good old BWRs get around this via direct cycle.
> Where the need for "maintanence" arise in this simple machine??
Pumps. Heat Exchangers. Valves. Flanges. Welds. Vessels. Graphite. Reflectors. Fission product processing equipment. Instruments/sensors. Control mechanisms. There are very complex systems with lots of things working together in a very tough environment (high radiation, high temperature). Maintenance is a major challenge.