Oh those uprates...

OVERKILL

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As I touched-on in my MCR vs refurb thread:

Bruce Power is working on uprating their units.

And how.

Unit 1 just came back from a maintenance break. This unit was already refurbished and returned to service in 2012, but it and its sister refurb'd unit, Unit 2, have lagged in output compared to their siblings, 3 and 4, being rated at 779 instead of 784, and 3 and 4 haven't run at 784 in ages, both of them have been well above 800MW for a very long time now.

Unit 1 came back at 816 rated, but then that was reduced to 789, while the unit was bouncing around above 800. It hit 810 yesterday and they've bumped rated capacity back up again, it is now 805. I fully expect to see it hit the low 820's at some point while still on the conventional fuel bundles.

As I noted in the other thread, all of the Bruce units are at 95%, they run a 5% derate due to fuel channel flow being unidirectional, not bidirectional like Pickering and Darlington. They are in the process of developing new fuel bundles with Cameco that may allow them to bump to 100% FP, which will be a game changer for the site and facilitate their 7,000MWe site output goal.

So, using some crude math (a 5% thermal derate does not directly translate into a 5% electrical derate, but that's what we are going to do for the sake of this discussion), if Bruce Power intends on a 870MWe rating for the A units, that puts them at 827MWe (roughly) at a 5% derate. So A1 has about 17MW to go to hit target. Bruce B5 has been into the 830's several times now, but the site goal for the B units is at least 880, so it needs to be ~836MWe to be on-target, not far off.

The units at Bruce have the highest thermal capacity of any CANDU ever produced at 2,832MWth, which put them above the 878MWe units (2,776MWth) at Darlington. They have some headroom, and capitalizing on that is the name of the game if they are to achieve the aforementioned 7,000MWe site output target.

It is fascinating watching this unfold in real-time; watching these units come back from routine maintenance breaks and produce significantly more power. One of the items addressed on Unit 1 was stator and rotor rewind for example, something pretty basic, but it made a big difference. Bruce 1 picked up 37MW according to the documentation I'm looking at, which means it should be able to hit ~825MWe with the derate factored in.

Yes, this unit was originally 750MWe:
Unit 1.jpeg


The old girl has legs and she continues to impress.
 

JHZR2

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Don't fully understand what you're telling us but just thinking running mechanical things at 95% capacity long term seems sketchy. Are wear parts seriously overbuilt?
There are at least two considerations. One is the heat generated in the windings, I^2 R. If the sensing systems are showing that the windings are within design limit, no issue. The other is transient response. Staying below 100% may have some benefits in terms of the system being able to better support if the grid has major transients.
 

OVERKILL

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Don't fully understand what you're telling us but just thinking running mechanical things at 95% capacity long term seems sketchy. Are wear parts seriously overbuilt?

100% FP is normal operating mode for a nuke.

When we talk about full power, it is not in the context of maxing out the generator but rather the reactor. It means 100% thermal capacity.

All of the uprates being discussed are with the original generator in place, as these are usually significantly oversized.
 

OVERKILL

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There are at least two considerations. One is the heat generated in the windings, I^2 R. If the sensing systems are showing that the windings are within design limit, no issue. The other is transient response. Staying below 100% may have some benefits in terms of the system being able to better support if the grid has major transients.

In the context of these units, the 5% isn't able to be utilized in a situation that would require more power. These units are able to rapidly shed 300MW each though, using steam bypass, to respond. That's irrespective of the thermal status of the unit, as full-power is maintained in that scenario. Bruce is the only of our plants that does this, though Darlington is technically capable of it as well.

This is a 5% thermal capacity derate, which of course also derates the electrical output, but it isn't 1:1 in reality, which I touched-on in the post, even though I used it like it was 1:1 for the sake of making the calculations easier.

Electrically, I believe the generators are probably gigawatt capable, but since I don't work at the plant, that's a WAG. The B units were originally designed to be 860MW/840MW NET, which, if you consider gross, would mean that the generators were sized to produce, at minimum, north of 900MW constantly. This means they are probably at least 950MW at 100% duty cycle, more likely higher than that, as they tend to be over-sized for the application. If they are the same as the ones at Darlington, those have been producing 880-890MWe NET since the late 80's and would have been oversized there as well.
 

OVERKILL

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@JHZR2 since you are interested in this, when I'm referencing registered capacity vs actual it's what is reported to the IESO for grid management/planning purposes vs what the unit is actually producing. I'll provide two snapshots here to illustrate.

1. Registered Capacity for all of the units currently online:
Screen Shot 2021-04-25 at 10.24.49 AM.jpg


2. Actual Output for all of the units currently online:
Screen Shot 2021-04-25 at 10.25.05 AM.jpg


So, just going over the units here:
Bruce A:
Bruce 1, which is the unit I've spoken about most, used to, like Bruce 2, be registered at 779. It's now registered at 805 and producing 809.
Bruce 2, still registered at 779, just a few MW over.
Bruce 3, offline for maintenance
Bruce 4, registered at 784 still, currently at 804

Bruce B:
Bruce 5: registered at 817, producing low 820's
Bruce 6: offline for refurbishment, went down with a big "880MW" label on the side, so this is one to watch.
Bruce 7: registered at 817, producing just under 830 today
Bruce 8: registered at 817, producing just under nameplate at 814 at the moment.

Darlington:
Darlington 1: Just back from a long maintenance outage after its world record run. Still ramping.
Darlington 2: recently refurbished unit, original generator, registered at 880, it's producing 878, which is pretty normal for this unit
Darlington 3: down for refurbishment
Darlington 4: this is the best performing Darlington unit, it has kissed 900MW several times, registered at 881, producing 884 right now

Pickering A:
Pickering 1: registered at 450 right now (it's had a fuelling problem the last few weeks, nameplate is 515) currently producing 449
Pickering 4: registered at 505 (a bit low, it should be 515) currently at 507

Pickering B:
Pickering 5: registered at just under nameplate (516) currently producing 513. This unit has been as high as 560MW when allowed to "run", which they've done a few times. It has a new turbine. Maximum sustained nominal for the current (original) generator is likely around 545MWe NET
Pickering 6: registered at 510 (should be 516) and producing 514
Pickering 7: also received a new turbine, but a fair bit longer ago than 5, currently registered at 530, we've seen it run up into the mid 530's, current at 525.
Pickering 8: currently down for maintenance.

If the 4x Pickering B units were refurbished, they'd all likely be capable of ~550 with the generators "freshened" (rewound like at Bruce A1) which would be performed as part of that process. New HP turbines would be expected for 6 and 8.

We are seeing the units coming back from maintenance, which is done during the low demand spring/fall periods to meet the summer peak, so full capacity will be with the return of Bruce 3 and Pickering 8. We will be down two units in a rolling fashion until the refurb's are done at Bruce and Darlington, so while we have 13,000MW of capacity, we won't see that again, perhaps ever, since Pickering is slated to shutter before the rerfurbs are done.
 
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