MSRE had a charcoal-bed off-gas system which safely stored all the noble gases. It was cooled and shielded with water, similar to today's PWRs. PWRs also have water chemistry control and resin-bed filters for primary loop which is highly radioactive and shielded. Construction of the off-gas system is described in pages 58-60 in ORNL-3708: Molten-Salt Reactor Program: Semiannual Progress Report for the Period Ending July 31, 1964 https://energyfromthorium.com/pdf/ORNL-3708.pdf