I thought BRP, Pathfinder and Humboldt bay were the true BWR1 units. I also thought Lacrosse and Elk River were the 'not BWR 1' early plants.
Weren't Shoreham and Millstone 1 also BWR 2?
And the other oddballs of Saxton, Shippingport, Piqua, Fermi 1, Bonus and ???
I would argue that was a pretext. Until ~ '92, utilities shut the plants down rather than face the cost of replacing the SG. After that, SG replacement became a 45 to 60 day turn around project. I doubt we will see any further early shutdowns from SG corrosion.
Actually, the predicted life up front was less than the unit life - it is stated in more than one FSAR. What happened in many cases is that they didn't even hit the expected 25 year life.
The NRC has a good page on the SG issues.
formatting link
Is the shroud removable, or is it welded in? The core internals on a PWR are replaceable, but I'm not sure how often it has been needed.
Millstone was a -3 (I think). BRP, Pathfinder and Humboldt Bay are too early to really be considered 'turn-key' designs. They were all one-of-a-kind, proof-of-something type plants. The -2/3/4/5/6 were/are from the 'turn key' power plant generation ('69 + ) where a utility would buy a nuclear plant 'turn key' from the NSSS vendor and AE. Many didn't really appreciate what they were getting in to and did it more for the prestige of having an "Atomic Power" plant in their portfolio.
But those early units didn't really fall into a BWR-XX category, they were one-of-a-kind designs.
Well, yes, you're right about there being a wide variety of early designs that have long been shutdown. Fermi 1 was liquid metal, Shippingport was a 'quick' adaptation of Naval design for political motives, and a host of others.
I think it's a combination of better turn around and higher capacity factors. Back in the '80's, if it took 200 days to do a SG job, and you only had a capacity factor in the 60-70 % range, the 'bean counters' would sharpen their pencils and say, "We'll never pay it back." But now, with a much higher capacity factor (most in the 90+ range), and shorter turn around, you're right, it is more economic to do the work and keep operating.
Well, for a $$PRICE$$, anything can be done :-) They are welded in. A sort of flat 'ring' around the bottom head / belt-line hold the circular arrangement of jet-pumps and the shroud. But depending where you want to try and cut it off, you'd have to either a) reach in a very tight place on the outside between the shroud and jet-pumps (or remove jet pumps??) or b) remove the lower core plate that directs the flow into the fuel bundles. And of course even with the fuel off-loaded, it's pretty 'hot' around all that steel that has been irradiated for many years.
Problem is, nobody's done it yet and the uncertainty/cost is a big 'unknown'.
Mark I BWR containments (those that look like an inverted light-bulb sitting in a doughnut) are now reviewing some issues with the torus steel developing fatigue cracks. A manageable issue, but just one more part of the plant that needs another inspection program. "Like my daddy always used to say to me, 'Little Rosanna Danna, If its not one thing its another' "
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.