If anyone is curious why the Beznau Operators were able to determine their PORV had failed open in only about 3 minutes (footnote 1), note the Beznau PORV had a mechanical position indication in the control room. So all they had to do was look at it. That info is in the Rogovin Report. (Specific reference can be cited if needed).
In 2 places you mention 'Potential Meltdown' of Davis Besse. (heading: The Davis-Besse Potential Meltdown. and heading Don't Rock the Boat: discussion). For years I wondered about that myself, if the PORV was never blocked and HPI never restarted in time. In Jan. of 2021 I finally decided to "just figure it out." It's not an easy calc (the arithmetic is easy). There are 2 ways to do it... something called Calculation of Decay Heat – Wigner-Way formula, and a DOE handbook calc. I did both. DOE calc result was 2.18 MWt/177 FA (fuel assemblies in core) or ~10KWt/FA (~6 2/3 kitchen toasters of heat/FA). The WW calc was ~5.8 kitchen toasters of heat/fuel assembly. I don't believe those kitchen toasters will melt a fuel assembly. I can send you both if you want to peer check.
True. but that's only because Davis-Besse was just starting up and had yet to build up a normal inventory of fission products. But that takes only a few full power days to do. So we were very lucky to get the warning in a very unusual situation. It was still a warning that should have been heeded.
In my experience as an Automation Engineer. PORV valves tend to have a massive hysteresis, in other words once they open at their setpoint pressure, they do not close until a much lower pressure is achieved. Personally I've seen a steam PORV open at 420kPa and not close again until around 160kPa.
And given that in that era it was not common for valves of any type to have position feedback sensors showing actual valve state in the control room - it was almost inevitable that at some point this scenario would happen.
Frankly this design flaw should have been picked up in a decent HAZOP process; that it wasn't and then the NRC proceeded to try and pretend otherwise - should have ended some careers.
Great explaination! For the first time I can actually understand what happened at TMI. THANKS JACK!
If anyone is curious why the Beznau Operators were able to determine their PORV had failed open in only about 3 minutes (footnote 1), note the Beznau PORV had a mechanical position indication in the control room. So all they had to do was look at it. That info is in the Rogovin Report. (Specific reference can be cited if needed).
Thanks, MIke. I somehow missed that. Any other corrections, additions solicited.
For those that have not guessed it already, mjd is the aforementioned Mike Derivan,
In 2 places you mention 'Potential Meltdown' of Davis Besse. (heading: The Davis-Besse Potential Meltdown. and heading Don't Rock the Boat: discussion). For years I wondered about that myself, if the PORV was never blocked and HPI never restarted in time. In Jan. of 2021 I finally decided to "just figure it out." It's not an easy calc (the arithmetic is easy). There are 2 ways to do it... something called Calculation of Decay Heat – Wigner-Way formula, and a DOE handbook calc. I did both. DOE calc result was 2.18 MWt/177 FA (fuel assemblies in core) or ~10KWt/FA (~6 2/3 kitchen toasters of heat/FA). The WW calc was ~5.8 kitchen toasters of heat/fuel assembly. I don't believe those kitchen toasters will melt a fuel assembly. I can send you both if you want to peer check.
True. but that's only because Davis-Besse was just starting up and had yet to build up a normal inventory of fission products. But that takes only a few full power days to do. So we were very lucky to get the warning in a very unusual situation. It was still a warning that should have been heeded.
In my experience as an Automation Engineer. PORV valves tend to have a massive hysteresis, in other words once they open at their setpoint pressure, they do not close until a much lower pressure is achieved. Personally I've seen a steam PORV open at 420kPa and not close again until around 160kPa.
And given that in that era it was not common for valves of any type to have position feedback sensors showing actual valve state in the control room - it was almost inevitable that at some point this scenario would happen.
Frankly this design flaw should have been picked up in a decent HAZOP process; that it wasn't and then the NRC proceeded to try and pretend otherwise - should have ended some careers.
Phil,
No deskpots get fired. It's close to illegal. You have to fire the entire NRC.