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PostPosted: Oct 16, 2009 12:24 pm 
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http://www.nytimes.com/2009/10/16/science/earth/16nuke.html?_r=2&ref=us
Quote:
The shield consists of 35 inches of concrete sandwiched between two sheets of steel, each of which is half an inch thick. Existing Westinghouse reactors, designed in the 1960s and ’70s, do not have shield buildings.

In another shift, the new design puts the emergency cooling water on the roof, so that no pumps are needed to deliver it in case of an accident.

Ed Cummins, vice president for regulatory affairs at Westinghouse, said that his company had designed the shield wall to meet a different commission requirement, that the plant be able to withstand the impact of an airliner. But the change had caused the commission staff to question the design’s adequacy to meet natural hazards.

Here is the NRC press release:
http://www.nrc.gov/reading-rm/doc-collections/news/2009/09-173.html

I tried to access the letter that the NRC sent to Westinghouse, but the document number didn't work.

As far as I know, the emergency cooling water was on the roof in previous versions of the AP1000 and AP600.

http://www.miamiherald.com/business/story/1285064.html
Quote:
Hannah said one concern was about potential building failure, regarding a large water tank mounted at the top of the structure that contains an estimated six to eight million pounds of water.

There were already delays announced because of questions by the NRC about the sump design.
http://greeninc.blogs.nytimes.com/2009/09/09/a-nuclear-renaissance-stumbles-forward/

The NRC only issued the rule about airliners earlier this year.
http://www.nrc.gov/reading-rm/doc-collections/news/2009/09-030.html


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PostPosted: Oct 16, 2009 11:44 pm 
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It is really important that Westinghouse work through this. The issue in question involves the use of the new "steel-plate/concrete" construction method, which allows almost all of the work needed to fabricate a reactor building to be done in a controlled factory setting with computer-aided manufacturing, as Westinghouse is doing right now in China (see the attached slides, which provide more information). This new construction method borrows very heavily from the modern ship-building industry, which also uses computer-aided manufacturing of steel-plate structural modules to construct new ships.

Attachment:
Nuclear Modular Construction 9-09.pdf [814.81 KiB]
Downloaded 1100 times


Besides enabling reduced construction cost and accelerated construction schedules, steel-plate reinforced structures also perform better than conventional reinforced concrete structures, particularly under beyond-design-basis loading where conventional concrete structures experience a cliff-like failure because once the concrete begins to fail it spalls away and provides no additional compressive strength. In contrast, steel-plate/concrete structures can continue to support substantial loads even when driven far into the inelastic response regime. That's why it's a great choice to use for a shield building that needs to be capable of withstanding the impact of a large commercial aircraft.

I'm not completely sure what the NRC's goal is in getting the AP-1000 into the New York Times and other major papers this way. This is a new technology, but there are clear technological and societal benefits from moving in this direction. It would be disappointing to see this bad publicity drive Westinghouse back to using older, more expensive, less effective technology.

Westinghouse is reported to be planning additional experiments to validate their models for how major elements of these structural systems perform (e.g., joints and connections). Possibly some design changes might be required as well.

This will be an important licensing issue worth watching closely, because it involves a new technology that will clearly transform nuclear construction as long as Westinghouse is successful in completing its licensing.

This is a perfect if small illustration of the dilemma we face in improving nuclear technologies, where lack of familiarity and experience can create major obstacles to introducing new technologies that have clearly better features than the existing approaches.

The conventional civil structural community is better at this. For example, over the decades we have seen steady and large improvements occur in the seismic safety of buildings. Demanding that a new design approach be perfect guarantees that no improvements ever occur.

The much more important issue relates to letting old technologies be grandfathered forward. The best thing that the NRC can do to improve the safety of future reactors, and foster other improvements, is to refuse to renew Design Certifications on old reactor designs without completely reopening the entire review process, including public hearings and the adjudicatory process. That's the way to encourage the vendors to improve their products (imagine today an automobile manufacturer selling cars without airbags simply because they had been able to renew their "design certification" every 15 years).


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PostPosted: Oct 17, 2009 1:46 am 
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I'll keep an eye on the web page and see if the actual letter to Westinghouse becomes available. Are you such the previous revision of the AP1000 that was approved didn't use this construction technique?

I'm also not too happy about the spin on this in the press. The Miami Herald headline said "Nuclear reactor design has safety flaw"

Also, It isn't clear to me that any redesign for plane strikes was actually required:

Quote:
Nuclear power plants are designed under very stringent requirements to assure they can safely shut down following “design-basis events” such as large fires, floods, earthquakes and hurricanes, as well as improbable equipment malfunctions including pipe breaks. These requirements include having two redundant systems to accomplish each safety function. The rule treats large commercial aircraft crashes as Abeyond-design-basis events.

http://www.nrc.gov/reading-rm/doc-collections/news/2009/09-030.html

As I recall, approaches to the shield building is already blocked from 3 of 4 directions by other buildings. It seems to me that you could just erect a wall on the 4th side, so there is no good avenue of approach to the building.


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PostPosted: Oct 17, 2009 2:04 pm 
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JoelUpchurch wrote:
I'll keep an eye on the web page and see if the actual letter to Westinghouse becomes available. Are you such the previous revision of the AP1000 that was approved didn't use this construction technique?


Yes, the previously approved design used conventional reinforced concrete, and would have trouble handling aircraft crash loads.

I expect that most of the work that is required involves additional experiments and analysis, but there may also be some design changes required. The way this is being reported is unfortunate.


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PostPosted: Oct 17, 2009 2:08 pm 
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I know, put a Phalanx CIWS gun at all four corners and set the fire-control threshold to 'paranoid' - that should keep the reactor safe. :lol:


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PostPosted: Oct 18, 2009 6:57 am 
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Per Peterson wrote:
Yes, the previously approved design used conventional reinforced concrete, and would have trouble handling aircraft crash loads.

I expect that most of the work that is required involves additional experiments and analysis, but there may also be some design changes required. The way this is being reported is unfortunate.


I doubt that it is simply reinforced concrete. Most reactors use pre-stressed concrete, which as far as I remember from several courses proved to be quite impact resistant...

_________________
Liking All Nuclear Systems, But Looking At Them Through Dark And Critical Glasses.


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PostPosted: Oct 18, 2009 10:53 pm 
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There is an article about this topic at The Energy Collective:

http://www.theenergycollective.com/TheEnergyCollective/49960

Quote:
Michael Johnson, director of NRC’s Office of New Reactors, told the news media in a conference call, “This is a situation where fundamental engineering standards will have to be met before we can begin determining whether the shield building meets the agency’s requirements.”

The agency said Westinghouse “has not demonstrated that certain structural components of the revised AP1000 shield building can withstand design basis loads.”

For some reason, I tend to interpret this this statement as meaning, "We don't understand the construction techniques you intend to use, therefore you have to build something we do understand". Hopefully, when the letter the NRC send to Westinghouse becomes available, there will be specifics to correct that impression. Frankly, I'm starting to get the impression that if the NRC was in charge of aviation, we would still be flying in bi-planes.

There are 14 reactors in the US alone that are in the queue waiting to be build using this design. Every year they aren't in operation, is another 100 million tons of CO2 that is being put into the atmosphere from coal fired generating plants. The proper question to ask, is what are the risks of not building these reactors?

On a related topic, you might want to read this post over at Depleted Cranium:
http://depletedcranium.com/hey-hey-ho-ho-the-nrc-has-got-to-go/#comments
You have to read down a way before he starts talking about the AP1000

I was thinking that this thread needs a link to my favorite You Tube video.
http://www.youtube.com/watch?v=K060qsK75kw
BTW, does anyone know if this is actually supposed to be represent a section of a reactor containment? I seen claims that it isn't.


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PostPosted: Oct 19, 2009 8:20 am 
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The letter from the NRC to Westinghouse still hasn't appeared, but I was doing a search through recent correspondence and came across a memo about a public meeting on the topic on the 28th.

Quote:
SUBJECT: PUBLIC MEETING WITH WESTINGHOUSE ELECTRIC COMPANY ON AP1000 DESIGN CERTIFICATION AMENDMENT - SHIELD BUILDING STRUCTURAL REVIEW
DATE & TIME: Wednesday, October 28, 2009 8:30 a.m. – 3:00 p.m.
LOCATION: The Legacy Hotel 1775 Rockville Pike Rockville, MD 20852

According to the agenda, the meeting will be open to the public between 8:30 and 10:30.

I've attached the memo about the meeting. It would be nice if someone who lived in the area could attend and post some notes from the meeting.


Attachments:
October28Meeting.pdf [106.07 KiB]
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PostPosted: Oct 25, 2009 3:53 pm 
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The letter is available on the web site now:

Quote:
October 15, 2009
Mr. Robert Sisk, Manager
AP1000 Licensing and Customer Interface
Nuclear Power Plants
Westinghouse Electric Company
P.O. Box 355
Pittsburgh, PA 15230-0355

Dear Mr. Sisk:

By letter dated August 31, 2009, Westinghouse submitted its design methodology report for the AP1000 shield building. The U.S. Nuclear Regulatory Commission (NRC) has completed its review of that report. Based on that report and the body of technical information reviewed to date, the NRC has determined that the proposed design of the shield building will require modifications in some specific areas to ensure its ability to perform its safety function under design basis loading conditions and to support a finding that it will meet applicable regulations (i.e., 10 CFR 50.55a and 10 CFR Part 50, Appendix A (GDC 1 and 2)).

Specifically, the design of the steel and concrete composite structural module (SC module) must demonstrate the ability to function as a unit during design basis events; the design of the connection of the SC module to the reinforced concrete wall sections of the shield building must demonstrate the ability to function during design basis events; the design of the shield building tension ring girder, which anchors the shield building roof to the wall, must be supported by either a confirmation test or a validated (or benchmarked) analysis method.

Progress on the NRC staff’s review of the shield building will require that Westinghouse provide modifications to the design and testing that demonstrate the capability of the building to perform its intended safety function under design basis loads. In addition to the issues described above, the NRC staff identified several other issues that need to be addressed; these issues are discussed in the enclosure to this letter.

Based on the above, the NRC considers its review of the shield building, as proposed, to be complete. The NRC will continue to support the resolution of the remaining issues on the AP1000 amendment application while the issues associated with the shield building are being addressed. The impact on the review schedule for the design certification amendment will be established after discussion with Westinghouse about its plans to address NRC’s determination.

Pursuant to 10 CFR 2.390, the NRC has determined that the enclosure may contain proprietary information or other categories of information that should be withheld from public disclosure. The NRC will delay placing this document in the public document room for a period of 30 days from the date of this letter to provide Westinghouse with the opportunity to comment on information in the enclosure that should be withheld from public disclosure. If Westinghouse believes that any information in the enclosure should be withheld from public disclosure, please identify such information line by line and define the basis pursuant to the criteria of 10 CFR 2.390. Based on Westinghouse’s response, sensitive information will be redacted from the version that will be made publically available.

Schedule impacts to the review schedules for the Combined License applications that reference the AP1000 amendment application will be addressed once the schedule for the design certification amendment is better understood.

Please note that the letter and the attached enclosure are proprietary. When the letter is detached from the enclosure, the letter becomes non-proprietary.


If I'm reading the letter correctly, then the NRC hasn't actually found any problem with the design of the shield building, but just that they feel that Westinghouse hasn't documented the design to their satisfaction.

Please note my previous post about the public meeting on October 28th about the AP1000 in Rockville Maryland.


Attachments:
ML09232020510.pdf [29.65 KiB]
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PostPosted: Oct 25, 2009 5:57 pm 
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JoelUpchurch wrote:

If I'm reading the letter correctly, then the NRC hasn't actually found any problem with the design of the shield building, but just that they feel that Westinghouse hasn't documented the design to their satisfaction.


The NRC is not satisfied with qualification testing of the design. A slight but expensive difference.


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PostPosted: Oct 25, 2009 8:38 pm 
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USPWR_RO wrote:
JoelUpchurch wrote:

If I'm reading the letter correctly, then the NRC hasn't actually found any problem with the design of the shield building, but just that they feel that Westinghouse hasn't documented the design to their satisfaction.


The NRC is not satisfied with qualification testing of the design. A slight but expensive difference.

Are you suggesting that the NRC will require Westinghouse to build some subsections of the shield building and subject them to design basis loads? Could the Chinese assist in this testing?


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PostPosted: Oct 26, 2009 1:28 pm 
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Short answer: Yes.


If Westinghouse can convince the NRC that it's computer modeling analysis codes are valid (this is quite possible I believe) they may accept that in lieu of actual scale model testing. Or a combination to validate certain portions of their computer models.

Again my personal opinion is the NRC is being overly conservative with this issue.


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PostPosted: Oct 26, 2009 3:05 pm 
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So how bad can full scale testing actually be? The building is modular. Would they have to fill it with stuff, or could they just build an empty shell next to the factory, and then hydro-test it? Or is the problem that NRC wants a shake test?

In the grand scheme of things, building an extra shell shouldn't be that big a deal. Testing, on the other hand, might be.


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PostPosted: Oct 28, 2009 9:27 pm 
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iain wrote:
So how bad can full scale testing actually be? The building is modular. Would they have to fill it with stuff, or could they just build an empty shell next to the factory, and then hydro-test it? Or is the problem that NRC wants a shake test?

In the grand scheme of things, building an extra shell shouldn't be that big a deal. Testing, on the other hand, might be.


Full scale testing would not be needed, and would be very difficult to do (there are no shake tables large enough, and it's not possible order up a design-basis tornado or hurricane). The key need here involves separate effects tests, to measure the strength of different elements of the shield building, likely including the connection to the foundation, the openings near the top where air enters for passive decay heat removal, and the connections between the vertical cylindrical sections and conical sections. These tests can confirm that the models for these structural elements used in the integrated modeling are accurate.

For more info on the current status of the AP-1000 shield building, see:

http://www.theenergycollective.com/TheE ... tive/49960

and

http://atomicinsights.blogspot.com/2009 ... r-for.html


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PostPosted: Nov 26, 2009 12:22 am 
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Westinghouse is making rapid progress in addressing the shield building issue. This is good news, since this new construction technology (steel-plate/concrete composite structures) will have a transformative effect on nuclear construction costs and schedules. From NEI Nuclear News:


Westinghouse Meets with NRC on AP1000 Shield Building Design
Nov. 19, 2009—Westinghouse is dealing with the technical issues the NRC raised
with the shield building design of its AP1000 reactor, an executive told the NRC
Wednesday.

“We are confident we can address and resolve all technical comments on the shield
building,” said Bruce Bevilacqua, vice president, engineering, at Westinghouse.
The NRC noted the progress Westinghouse had made with the technical issues described
in an NRC press release in October (see Nuclear Energy Overview, Oct. 22).
“Westinghouse appears to have taken our concerns seriously,” said Laura Dudes,
deputy director, engineering division, at the NRC. “They have acknowledged the need
for modifications to enhance the shield building design.”

In October, the NRC said Westinghouse “has not demonstrated that certain structural
components of the revised AP1000 shield building can withstand design basis
loads.” The NRC added that “progress on the shield building review will require the
company to provide modifications to the design, as well as testing that demonstrates
the building will perform its intended safety function under design basis loads.”
This week’s meeting was the first step in a “technical dialogue” designed to resolve
these issues.

“Today’s discussion is a good first step to introduce the new design features for the
shield wall and begin a technical dialogue on engineering methods, analysis and testing,”
Dudes said. “However, the resolution of these issues will require a comprehensive
technical submittal from Westinghouse demonstrating how the new design addresses
both accident conditions and aircraft impact. It will also require … an in?depth
technical review by the NRC.”

The shield building protects the containment and provides structural support to the
containment cooling water supply. It is made of steel and concrete in what is known as
a steel composite design that is about 73 feet high and about three feet thick.

Bevilacqua said that the primary functions of the shield building were to provide passive
cooling and radiation shielding but that it also had to protect against “tornadoes,
seismic events and, of course, aircraft impact.”

“We are very much focused on making this an integrated structure that provides all
of its functions structurally,” said Bevilacqua.

In response to the NRC letter, Westinghouse has “actively and aggressively” done a
revaluation of the shield building, including soliciting the advice of outside experts
from the Shaw Group, Purdue University and other organizations, Bevilacqua said.

Some of the design enhancements Westinghouse have made include:
• adding shear-reinforcing tie bars so that the shield building acts as a single unit
• increasing the thickness of the steel?concrete composite plate that surrounds the
building to protect against buckling
• improving the connection between the base of the building and the reinforced
concrete roof.
Westinghouse is also conducting a series of 12 tests to ensure the building design is
safe.

Bevilacqua said that Westinghouse would go through a detailed technical review of
the shield building design in a proprietary meeting with the NRC conducted after the
public meeting.

“We are focused on demonstrating that the AP1000 shield building design is safe,
robust and meets regulatory requirements,” Bevilacqua said.

Enhancements to the shield building will be addressed in a revised integrated AP1000
shield building report from Westinghouse to be submitted to the NRC in January.
Westinghouse expects to receive approval of all design amendments to support the
first AP1000s coming online in the U.S. in the 2016 timeframe.
The slides for the public presentation given by Westinghouse along with more
information on the AP1000 design can be found here http://ap1000.westinghousenuclear.com/ap1000_nui_reg.html. << Thaddeus Swanek,
tjs@nei.org


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