Reactor Coolant Pumps for AP1000 still a problem
This is a story that I really don’t want to tell, but bad news is like old fish. It doesn’t smell any better as it ages.
All eight AP1000 construction projects are at risk “for want of a nail.”
In this case the nail is a reactor coolant pump, the largest one in the world, equipment that evidently doesn’t exist and for which there is only one supplier.
In May 2010, Nuclear Engineering International published an article that announced that the coolant pumps for the first AP1000 reactors had been successfully tested at normal operating temperatures and pressures. Those tests were witnessed by the customer.
But RCPs were a significant topic during the July 30 investor call held by Curtiss-Wright (NYSE:CW) on its second quarter earnings, five years after the triumphant announcement that testing had been completed.
The company’s presentation during the call included the following statement from chairman, president and CEO David Adams [no relation]:
Regarding an update to our long-term operating margin guidance, we are not prepared to provide any target at this time. As the AP1000 program is quite significant to our future growth rates, we need to finalize the pending China order before fully resetting long-term expectations for margin growth….
Next I would like to provide an update on the AP1000 program. Overall we continue to make progress in the production of our first of a kind reactor coolant pump or RCP, supporting the AP1000 nuclear program. We have successfully completed the engineering and endurance testing phase and are now working with our customer and the Chinese as we evaluate the results of those tests. We expect to begin deliveries of our RCPs to China in the latter half of the third quarter. Regarding our next AP1000 order, we anticipate contract negotiations to resume once we begin shipping pumps and remain hopeful for the order by the end of the third quarter.
CEOs of public companies are required to inform investors about issues that can materially affect their finances. That task is not always easy or welcome.
Preparing the exact wording can require an almost unbelievable amount of effort and is often a painful process for several players who must contribute. It takes experience and discernment to unravel the words.
Adams was providing forward-looking statements using words that clearly indicated he was making predictions based on currently available information. As earnings statement disclosures warn, predictive statements might not be correct.
“Working with our customer” and “expect to begin deliveries” are statements indicating that work is not only incomplete, but still somewhat undefined.
Uncertainty about completion became even more apparent during the Q&A period, as Adams answered related questions:
I said on the last call as well that we had anticipated that we would get through the E and E testing and we did over the end of last quarter and that was excellent. We were very happy. We proved out the design modifications that we had made at that point. The thrust runner, bearing and so forth. The whole purpose was to go through and to really prove that we got a 60-year-life pump.
And so everybody’s happy that we did accomplish that. And now as a result we are doing some tweaks and we anticipate that we are going to be shipping hardware in the very near term to China. And that was always the premise with our customer both domestic and China that once we started shipping product that met the requirement (of efficiently passing the E and E testing) then we would be starting resuming negotiations. So you’ve heard me say before I’ve been cautiously optimistic; I remain so. And third quarter is still what we are looking at to pick up an order as I indicated. We’re going to be shipping hardware pretty soon.
For anyone who is experienced in nuclear energy-related engineering and quality assurance programs, “doing some tweaks” is a red-flag statement.
It means that changes may still be necessary. There are few changes that can be made to critical equipment without going back into the testing and evaluation phase.
Because of the critical nature of these pumps and the harsh working environment that they must endure during their 60-year design life, testing and evaluation are time-consuming endeavors.
The current redesign and retesting effort began sometime before April 2014 when statements issued by the responsible companies indicated that some pumps that had already been delivered to China passed post installation testing and others did not. That was almost 18 months ago.
As Curtiss-Wright statements indicate, there will not be any new AP1000 commitments until after the coolant pumps have been proven. Customers have growing reasons to wonder if that finish line will be reached before they run out of patience or money.
When contacted via email about the reactor coolant pump situation described above, a Westinghouse spokesperson offered the following:
Construction of four AP1000 units in China continues to move forward at an impressive pace, with milestones being achieved on a regular basis. The related RCP issue is being resolved by all parties working together in the safest and most timely manner possible. Westinghouse does not comment on confidential project or commercial matters. Westinghouse remains focused on, and committed to, the safe and successful delivery of AP1000 units in China and around the world.
Let’s hope that the parties are working together to complete their work safely and effectively in the very near future.
The above article was first published in the August 20, 2015 issue of Fuel Cycle Week and is republished here with permission.
At least Senator Ed Markey no longer needs to worry about the Chinese getting strategic technology (large canned pumps). ?
Seriously, these issues usually get worked out and the follow on units reap the benefit.
Seriously, these issues usually get worked out and the follow on units reap the benefit.
Maybe. Unfortunately, there are eight very large investments riding on getting these issues resolved in the relatively near future. For at least one unit, the RCPs are probably already on the critical path, so every day of delay is a day of delay in start-up and a day of delay before commercial operations.
That gets very expensive very quickly. I don’t know when the critical path for the other units catches up to the RCPs, but you can see how this problem can be a real bugaboo for the large PWR industry.
It’s a very interesting industrial chicken-and-egg problem. If nobody committed to building nuclear plants that need these RCPs, there’d be no market for them, and so, no way to justify the massive investments to bring these very expensive engineered products to market. However, once companies have committed to building a nuclear plant for $12Bn, they are now at risk of the company that promised the RCPs being unable to either deliver on time, or possibly unable to deliver EVER if the company collapses because of problems bringing the design to market.
However, if the AP-1000 CAN get past these initial growing pains, it will have a strong first-mover advantage against any later reactor designs, because they will have to face similar uncertainty problems in a market where the AP-1000 has already been proven and the supply chain is in place and functional.
“The whole purpose was to go through and to really prove that we got a 60-year-life pump.”
See what a pain in the ass, not having an easy option to replace a part if it falls a bit short of expectations. Imagine if they had a pump designed for 60 year life, tests suggested it should last 40–100 years and they could easily replace it at 20 years if necessary. Furthermore, perhaps something might be learned in the next 20 years that makes the future pumps even more reliable. Locking big parts up inside re-bar reinforced concrete mausoleums has serious cost and schedule consequences.
“For anyone who is experienced in nuclear energy-related engineering and quality assurance programs, “doing some tweaks” is a red-flag statement.”
This is the sign of a broken technology development process. All great industries evolve by doing tweaks on a daily basis. That’s how improvements get into your product and production processes. The fact that the benefits of tweaking or introducing design improvements is verboten in nuclear energy related engineering is the red flag. It means the regulatory process is stifling improvements. Sometimes you tolerate some stifling to gain consistency and predictability, but stifling is a very strong medicine with terrible side effects. It means you will eventually be made extinct by a faster evolving competitor.
Thanks for continuing to report on this. As you say, if this isn’t fixed soon it could be a very big deal.
I wonder how similar the design of the CAP1400 RCP is to the Curtiss-Wright APR1000 pumps?
Good question. I’ll see what I can find out.
Yes, the Chinese seem quite confident going forward with the CAP1400. But they might not have fully understood the impact of the pump problem.
” The fact that the benefits of tweaking or introducing design improvements is verboten in nuclear energy related engineering is the red flag. It means the regulatory process is stifling improvements.”
At times I have wondered what benefit lawyers have provided to modern society. Do they help provide the path to doing things right or are they just blood sucking parasites stymying the path to a brighter tomorrow? The devil is in the details. Great things may be derailed by minutia.
Though those rules make changes expensive and length their implementation, they help to improve safety. Shown by e.g. the big safety improvements in the airline industry, which has similar rules.
The reason; such design improvements do turn out sometimes (or often) to be no improvement at all.
And, of course although it was not related to you question to Westinghouse they had to use the word safe, or safety twice in one short paragraph. I think there is a rule now in the industry that the word safe must occur in every other sentence.
Perhaps this is one of the tweaks: new O-Rings:
I think the AP1000 RCPs have no seals; that is a feature of canned motor pumps. That is why they went in that direction, to eliminate RCP seal maintenance and target a 60 year pump life. The new W seal designs are intended for the older RCPs with shaft seals. Intent is to extend the time to seal failure for events causing a total loss of all seal cooling. For those events the RCP shaft seal is the weakest link leading to RCS pressure boundary failure. Reduced maintenance and seal failure are the whole driving force behind going to canned motor pumps. The motor can is actually part of the RCS pressure boundary, thus no shaft seal is required. Much, much smaller canned motor pumps have been used for years and much experience has been gained with their use. The current problems are related to scaling the concept up to the large size needed for the AP1000. Additionally the AP1000 is a 2-loop plant. This deviates from older W philosophy of adding an additional (smaller but proven tech) loop to increase plant size.
“The motor can is actually part of the RCS pressure boundary, thus no shaft seal is required”
I don’t understand this. Does this mean that the entire pump is liquid filled, including the motor? Or is the sealed motor encased within the pump’s own casing? I just don’t see how a seal-less shaft is possible. Not sayin’ it ain’t so, just saying I don’t understand.
The pump motor is filled with primary coolant. It is an induction motor with a canned stator to protect the windings from exposure to that water. There is a barrier of sorts that prevents most flow from the main, high temperature coolant system into the pump motor, but it is not intended to be leak tight. The pressure boundary thus is the can surrounding the motor and sealed to the pump.
These machines are about 20-30 times as large as the ones that I’m familiar with, but “only” about ten times as large as the largest with extensive operating history. They also have a heavy flywheel on the rotor, a feature designed to meet “conservative” modeling assumptions about pressures and temperatures in the event of a complete loss of AC power. The flywheel gives the pump more momentum and keeps flow going during the transition to natural (passive) circulation for long term cooling.
None of the canned pumps I know of have heavy flywheels. Perhaps they complicate balancing these close tolerance, 90 ton pieces of rotating machinery.
These pumps actually have 2 inertia flywheels, one at top and one at bottom. Probably easier engineering all things considered. The actual rotating assembly will be considerably less than 90 tons (balancing), but even then it pales in comparison to the rotating weight of a 1000MW Turbine Generator, which are fairly easy to balance using today’s tech. My guess is the flywheels weight (and canned design) are more of a thrust bearing design headache. In an RCP with shaft seals all the rotating weight hangs off the thrust bearing. When static, the RCS P tries to eject the pump from the system. When running the impeller force counter balances that (pulls into the system). In a canned pump the “ejection” force is on the can, pump running or static. So it is a totally different thrust bearing engineering problem. Do I remember the current “bug” is some sub component of the thrust bearing?
Seems to me that such a system may be problematic in the sense that if either component, (the pump or the motor), experiences a breakdown, both components must be subjected to dismantlement and repair. Or maybe I just don’t “get it”. But I know from my own experience that individual components of a whole machine are far easier to repair if they are autonomous in structure to the machine as a whole. A good example is GM’s V-8s. The old generation had a mechanical fuel pump attached to the dude of the block. Easy to change, and simple in structure. But today’s generation has no fuel pump mounted on the engine. Indtead, the fuel pump is mounted internally within the fuel tank. So now, to change a fuel pump one must pull the fuel tank, mess with the electronics controlling the fuel gauge, and fuel delivery system, and risk subsequent computer glitches. An improvement?? Hardly.
I’ve been meaning to post this for two weeks on this topic – a detailed, illustrated explanation of the AP1000 canned rotor pumps: http://www.ewp.rpi.edu/hartford/~ernesto/F2011/EP/MaterialsforStudents/Stack/Baumgarten2010.pdf
Thanks Rod and mjd.
Large rotating equipment in containment is always a bad idea. The best large reactor design is ESBWR because it relies on natural circulation. The best small reactor design is NuScale SMR because it too relies on natural circulation. Anything else is problematic. Large RCPs for PWRs and large RWR pumps for ABWR will always be a source of headaches.
…and yet, we seem to have nearly hundred of the darn things that seem to just keep spinning along. In this country alone.
I hear you on ESBWR and NuScale. But neither have yet been built, and in any event GEH recommends ABWR for tight load-following applications. GEH is also working first on getting general design certification for ABWR in the UK, as the grid there is optimized for plants of about a GW: at 1.6 GW ESBWR could cause issues if it goes off-line in an unscheduled manner. (One of the criticisms of EPR.)
Hum, I would expect anything planned for completion after the EPR to benefit from it’s experience introducing 1,6 GW of power on the UK grid, and that it won’t be anymore a real problem by then.
Well… I would too. ‘Cept UK EPR isn’t a done deal quite yet, and if for any reason EDF’s financing falls through, the whole UK bidding process will likely be re-opened.
All the EPR projects appear to have trouble with out-of-spec carbon content in the reactor vessels.
If the EPR goes nowhere but the AP1000 succeeds, a 3-unit AP1000 site is roughly equivalent to a 2-unit EPR site.
All, except the Finnish EPR.
That reactor vessel was not produced by Areva.
I was thinking the same thing as I read this article. I know that Fermi 3, in my home state of Michigan, is the first approved COL for the ESBWR. Since DTE Energy is in no hurry to build, it looks like North Anna will be the first ESBWR constructed.
@poa August 30, 2015 at 10:55 PM
“Seems to me that such a system may be problematic in the sense that if either component, (the pump or the motor), experiences a breakdown, both components must be subjected to dismantlement and repair. Or maybe I just don’t “get it”.”
I think you get it just fine. The design goal for this pump was to be failure and maintenance free for 60 years. A pretty ambitious target when you scale up a small, very reliable design concept to “world’s largest.” A reasonable goal? Depends… Murphy would say no. I’m still watching and focused on how much they have got right so far. They have a problem with one small sub-part, manufactured by one sub-vendor, that has been attributed to a QA breakdown. A very solvable engineering problem, given enough time and attention. But as Rod has pointed out it is a race, TBD the price of beans. And the whole nuke world is watching.
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