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RE: A line I heard recently regarding MSR maintenance is: "You'll need robots to do the maintenance of your maintenance robots." Another memorable gem is "If yo

RE: A line I heard recently regarding MSR maintenance is: "You'll need robots to do the maintenance of your maintenance robots." Another memorable gem is "If you can make robots that can do that, you should just sell the robots" Maintenance of MSRE was done by humans without much downtime or exposure[1]. Ease of maintenance is a function of design. Just design it carefully. [1] https://energyfromthorium.com/pdf/NAT_MSREexperience.pdf https://energyfromthorium.com/pdf/NAT_MSREexperience.pdf

acidburnNSA 7y ago
MSRE had fans blowing on pipes as cooling. It had no real fluid-to-fluid heat exchanger or power conversion cycle, which is where lots of maintenance troubles arise from. Furthermore, they were in the 1960s, before the NRC existed and before we worried about ALARA. Furthermore, MSRE cannot to this day account for about half of their radioiodine inventory. Furthermore, Alvin Weinberg himself says in his 1990s autobiography, The First Nuclear Era (amazing read btw) that they were just piping radioactive gas into the forest nearby back then (or, wait, was that the aqueous homogeneous reactor? I forget, I left all my copies of that book at the office...). A lot has changed since MSRE ran, and MSRE was a fairly simple experiment to prove a concept. It didn't have all the systems necessary to make practical energy, and so it didn't have the maintenance issues you'd expect. Also, it only ran for like 5 years, vs the 60-80 we're hoping for these days from these facilities (inherently requires lots of maintenance). Have you ever done work planning for ALARA at a light water reactor? Those who have raise eyebrows really high when academic reactor designers start saying how easy the maintenance will be. Admiral Rickover's quotes from 1953 just keep on coming back to haunt us [1]. He didn't curse us to death, but he sure warned us that we need to be working really hard on new/effective solutions to these kinds of problems. Most advanced nuclear advocates skip over these points. RE: Design it carefully: This takes practical experience. The number of people today designing new reactors who have this kind of experience is very close to zero. We will have to re-learn. [1] https://en.wikiquote.org/wiki/Hyman_G._Rickover#Paper_Reactors,_Real_Reactors_(1953) https://en.wikiquote.org/wiki/Hyman_G._Rickover#Paper_Reacto...
- pfdietz 7y ago
  The radioactive gas was probably noble gases like krypton and xenon. They'd have to be careful with the xenon, as 137Xe decays to dangerous 137Cs (halflife 3.8 minutes). The idea "all the radioactivity stays in the salt" can be wrong, as that xenon could deposit the cesium outside the salt if it bubbles out quickly enough. 135Xe also can be removed (halflife ~9.2 hours). It is famously a very powerful neutron poison with important effects on reactor operation; those advocating thermal breeders count on it being removed before it soaks up neutrons. But this leads to an increase in production of its decay product, 135Cs, which has a halflife of 2.3 million years.
  - achalhp 7y ago
    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 https://energyfromthorium.com/pdf/ORNL-3708.pdf
- achalhp 7y ago
  RE: Furthermore, they were in the 1960s, before the NRC existed and before we worried about ALARA. "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." This is within the ALARA standards. http://moltensalt.org/references/static/downloads/pdf/NAT_MSREexperience.pdf http://moltensalt.org/references/static/downloads/pdf/NAT_MS... RE: no real fluid-to-fluid heat exchanger. MSRE had salt-to-salt and salt-to-air heat exchangers made from hastelloy-N. https://www.flickr.com/photos/oakridgelab/31537153147/ https://www.flickr.com/photos/oakridgelab/31537153147/ RE: or power conversion cycle, which is where lots of maintenance troubles arise from. That's the part which is not highly radioactive. Fluid fuel reactors have simplest fuelling mechanism of any reactors. The fuelling of a fluid-fuel reactor is even simpler than fuel injectors of diesel engine. Where the need for "maintanence" arise in this simple machine?? Only moving parts are the pump impellers and the control rods. ORNL had some difficulty designing the bearing, seals etc. for the salt pump. But, even that is solved today with concentrating-solar salt pumps.

acidburnNSA 7y ago

MSRE had fans blowing on pipes as cooling. It had no real fluid-to-fluid heat exchanger or power conversion cycle, which is where lots of maintenance troubles arise from. Furthermore, they were in the 1960s, before the NRC existed and before we worried about ALARA. Furthermore, MSRE cannot to this day account for about half of their radioiodine inventory. Furthermore, Alvin Weinberg himself says in his 1990s autobiography, The First Nuclear Era (amazing read btw) that they were just piping radioactive gas into the forest nearby back then (or, wait, was that the aqueous homogeneous reactor? I forget, I left all my copies of that book at the office...). A lot has changed since MSRE ran, and MSRE was a fairly simple experiment to prove a concept. It didn't have all the systems necessary to make practical energy, and so it didn't have the maintenance issues you'd expect. Also, it only ran for like 5 years, vs the 60-80 we're hoping for these days from these facilities (inherently requires lots of maintenance). Have you ever done work planning for ALARA at a light water reactor? Those who have raise eyebrows really high when academic reactor designers start saying how easy the maintenance will be. Admiral Rickover's quotes from 1953 just keep on coming back to haunt us [1]. He didn't curse us to death, but he sure warned us that we need to be working really hard on new/effective solutions to these kinds of problems. Most advanced nuclear advocates skip over these points. RE: Design it carefully: This takes practical experience. The number of people today designing new reactors who have this kind of experience is very close to zero. We will have to re-learn. [1] https://en.wikiquote.org/wiki/Hyman_G._Rickover#Paper_Reactors,_Real_Reactors_(1953) https://en.wikiquote.org/wiki/Hyman_G._Rickover#Paper_Reacto...

pfdietz 7y ago
The radioactive gas was probably noble gases like krypton and xenon. They'd have to be careful with the xenon, as 137Xe decays to dangerous 137Cs (halflife 3.8 minutes). The idea "all the radioactivity stays in the salt" can be wrong, as that xenon could deposit the cesium outside the salt if it bubbles out quickly enough. 135Xe also can be removed (halflife ~9.2 hours). It is famously a very powerful neutron poison with important effects on reactor operation; those advocating thermal breeders count on it being removed before it soaks up neutrons. But this leads to an increase in production of its decay product, 135Cs, which has a halflife of 2.3 million years.
- achalhp 7y ago
  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 https://energyfromthorium.com/pdf/ORNL-3708.pdf
achalhp 7y ago
RE: Furthermore, they were in the 1960s, before the NRC existed and before we worried about ALARA. "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." This is within the ALARA standards. http://moltensalt.org/references/static/downloads/pdf/NAT_MSREexperience.pdf http://moltensalt.org/references/static/downloads/pdf/NAT_MS... RE: no real fluid-to-fluid heat exchanger. MSRE had salt-to-salt and salt-to-air heat exchangers made from hastelloy-N. https://www.flickr.com/photos/oakridgelab/31537153147/ https://www.flickr.com/photos/oakridgelab/31537153147/ RE: or power conversion cycle, which is where lots of maintenance troubles arise from. That's the part which is not highly radioactive. Fluid fuel reactors have simplest fuelling mechanism of any reactors. The fuelling of a fluid-fuel reactor is even simpler than fuel injectors of diesel engine. Where the need for "maintanence" arise in this simple machine?? Only moving parts are the pump impellers and the control rods. ORNL had some difficulty designing the bearing, seals etc. for the salt pump. But, even that is solved today with concentrating-solar salt pumps.