UCS's Lochbaum shares insights on Davis-Besse Shield Building cracking

Dave Lochbaum, director of the UCS Nuclear Safety Project, is one of the nation's top independent experts on nuclear power. On Nov. 4, 2015, David Lochbaum of the Union of Concerned Scientists (photo left) shared the following insights regarding the severe, and worsening, concrete cracking in FirstEnergy Nuclear Operating Company's Davis-Besse Shield Building. Lochbaum has granted Beyond Nuclear permission to reproduce his insights here.

"I happened just yesterday to skim through BOP (bunches of papers) that FENOC buried, I mean submitted to, ACRS. The BOP is online at https://adamswebsearch2.nrc.gov/webSearch2/main.jsp?AccessionNumber=ML15280A293

There's a 16 page attachment to the letter transmitting the BOP to the ACRS that seems to lay out the landscape pretty well. This 16-pager is [linked here]. 

The first paragraph on page 1 includes nifty phrases like "...help facilitate a solid understanding of how Davis-Besse is currently managing the Shield Building laminar crack issue..." and "...how the Shield Building Monitoring Program will ensure that the identified aging mechanism will be managed...".

The remaining 15 pages reveal plenty of reasons to question whether the "solid understanding" will actually "ensure" anything good.

The third paragraph on page one explains that cracking was first identified in October 2011. The backgrounder kinda glosses over how the discovery was made when cutting through the shield building wall. Nor does it explain how the cracking -- blamed on a freak winter storm in the late 1970s -- hid itself when the shield building wall was cut open a decade earlier when the original degraded head was replaced. This knocks a few points off the "solid understanding." How did a crack allegedly formed in the late 1970s hide itself in 2002-2003 and then reveal itself in October 2011?

The first paragraph on page two explains that falling concrete could affect the Auxiliary Building and/or the Borated Water Storage Tank. The backgrounder does not explain the potential "affect" but it's safe to assume it won't be positive.

Section C on page three points out that "To establish a design basis calculation, two key pieces of information would be required: 1) The extent of laminar cracking had to be established...". Actually, the text leaves out an important adjective. One can establish a design basis calculation without a clue to the extent of laminar cracking. But one needs to know the extent of cracking to establish a CREDIBLE design basis calculation. It's not apparent that FirstEnergy has truly defined the extent of laminar cracking. Hence, it's not clear that they have a credible design basis calculation. 

Doubts about the extent of laminar cracking can be found in the text in the middle paragraph on page three -- "Impulse Response techniques were used to map the entire accessible areas of the exterior Shield Building..." and "The Impulse Response map completed in 2012..." and in the  text in the first two paragraphs under Section F on page eight -- "Based on the first root cause conclusions, the laminar cracking was considered passive" and "Monitoring in 2012 did not identify any changes in cracking. However, in 2013, a new crack was identified in a core bore that previously did not have indications of cracking."

Recurring surprises does not equate to a "solid understanding" that "ensures that the identified aging mechanism will be managed." The recurring surprises do equate to NOT knowing the extent of laminar cracking. And NOT knowing the extent of laminar cracking, per FirstEnergy's own statement, equates to NOT having a credible design basis calculation.

The last three paragraphs on page eight point out that FirstEnergy does not have their arms around this situation: "The Shield Building Monitoring Program was revised to increase the number of cores to be inspected to 23 core bores. These nine additional core bores were added to monitor the condition."  And "The Shield Building Monitoring Program was revised in 2015 to address changes in the Shield Building. Currently, the program is monitoring a total of 28 core bores. ... Five additional core bores were added to monitor the leading edges of areas of crack propagation."

"...the laminar cracking was considered passive" but requires more and more and more core bores "to monitor the leading edges of areas of crack propagation."

If these antics constitute having a "solid understanding" of the "extent of laminar cracking," what would merely guessing look like?

Recall that Section I on page three described the Impulse Response techniques used to develop a map that "shows the extent of laminar cracking." That section ends with the sentence "This Impulse Response map is used in subsequent analyses."

There's no mention of re-doing the Impulse Response process to re-map the extent of laminar cracking. Yet new cracks were said to have been found in 2013. So, is FirstEnergy still using a map known to be obsolete in its analyses?

The middle part of page nine describes "Fourteen areas of potential crack propagation" and various core bores planned to provide insights on the extent of laminar cracking.

Why not repeat the Impulse Response process to map out the current extent of laminar cracking?

If the Impulse Response map is not as useful as core bores in monitoring the extent of cracking, why use the old map in analyses?

The last paragraph on page nine states "In summary, the implementation of the Shield Building Monitoring Program will provide reasonable assurance aoerf fwih gsuhfsu [sorry, I couldn't type while I was laughing so hard] that the existing environmental conditions jusgfs uahas opsjha [sorry, another fit of laughter] will not cause aging effects that could result in a loss of component intended function."

So, the real question that ACRS should seek to answer is what has the largest crack?

A) The Shield Building at Davis-Besse

B) The Shield Building Monitoring Program for Davis-Besse

C) All of the above.

Even dead, Shakespeare knows the answer to be B.

If information is power, FirstEnergy seems powerless to understand the extent of laminar cracking and therefore properly manage aging effects.

Thanks,

Dave Lochbaum

Director, Nuclear Safety Project

UCS"