SQUG spent decades on seismic (earthquake) risk evaluations – effort continues

The six months since Fukushima has brought out a certain class of professional worriers who ignore history to fret about topics that have already been the source of concern for many years. In this particular case, the worriers want to assert that nuclear power plants are uniquely vulnerable to the effects of earthquakes, which are natural events that have always occurred on our home planet. They also happen to be events that affect ALL structures. The earth is neutral; it does not specifically target nuclear power plants when its plates rub together.

Please understand that I am not patting people on the head and and falsely reassuring them, but it would be nice if the worriers would do a little homework instead of appearing to assume that they are the first ones who noticed that the earth moves around every once in a while.

Earthquake effects and seismic qualification for complex structures, systems and components, especially ones that carry hazardous fluids like steam, extremely hot water, toxic chemicals and radioactive fluids have been topics of intense study and implementation efforts in the fields of structural, mechanical, electrical, instrumentation, nuclear engineering and civil engineering for decades.

By the time that fission was discovered, the science and engineering principles associated with seismic resilience were pretty well developed. The codes and standards that were developed were not always well enforced in all structures, but the nuclear profession attracted careful engineers and project managers who were NOT judged on their ability to scrimp on engineering or materials in order to reduce costs.

Given the budget and the opportunity, most engineers will include generous margins and build “bullet proof” structures. I live and work among people who take pride in their work and love the fact that they are encouraged to make sure their creations can survive anything that nature can dish out.

A few days ago, I had a long conversation with Howard Shaffer, a retired nuclear engineer with about four decades worth of experience. He is a registered professional engineer in four states. He told me about a recent visit that he made to Mineral, VA to visit with some relatives. While there, he made a trip to the North Anna visitor center to find out more about the actual damage discovered at the plant following the August 23, 2011 earthquake. Howard told me that the only damage found was in the turbine building, which is not a seismically qualified, safety-grade structure. The “damage” consisted of a small chunk of concrete that was dislodged from the foundation of a tank.

The North Anna visitor center spokesman was confused, however, by the fact that the plant was not being allowed to restart, despite the report to the NRC that no damage had been found. As Howard and I discussed, the NRC, especially its current Chairman, is full of those kinds of professional worriers who think that their concerns have never been addressed because they fail to do much homework to find out what has been done before they arrived on the scene. The impact of the delay in restarting North Anna units 1 and 2 is about $2 million per day in extra sales for the fossil fuel industry.

Howard then talked about an effort that he had worked on a few decades ago called the Seismic Qualification Utility Group (SQUG). He told me that one of the things that the group learned by visiting both nuclear plants and other large industrial facilities like refineries and chemical plants with similar kinds of piping and equipment is that properly engineered, constructed and secured industrial facilities are rarely, if ever, damaged in even the largest earthquakes.

When I had a chance, I let my fingers do the walking to find out more about the SQUG, its findings and its recommendations. The group was initially formed in response to Unresolved Safety Issue (USI) A-46, Seismic Qualification of Equipment in Operating Nuclear Power Plants. That USI was issued in 1980, while I was still in college, during another period when the NRC was led by professional worriers who saw their role as inhibitors vice enablers of nuclear energy development.

A group of 15 utilities who owned nuclear plants put together an “A-team” of engineers and scientists to develop a reasonably cost-effective response to the challenge that their predecessors had not known what they were doing when they designed and built the plants. Dominion, the owner of the North Anna facility, is a member of the group. The SQUG is still active. The group has turned out a huge library of papers and has regularly reported its finding to the Nuclear Regulatory Commission (NRC).

There are thousands of documents in the Agencywide Documents Access and Management System (ADAMS) data base that deal with seismic qualifications and efforts to respond to USI A-46. In 1987, after five years of effort, the NRC issued Generic Letter (GL 87-02) accepting the SQUG methodology for responding to USI A-46 on a case by case basis. The effort has not been static; there have been continued reviews and updates as new information has been developed and experience gained. SQUG “continues to maintain the validity of and support and broaden the use of earthquake experience data as a cost-effective method for seismic qualification”.

I also looked across the web to learn about the group and its findings. The paper that shows up at the top of the list in a Google search using the term “squg seismic qualification utility group” is a twenty year old paper titled The Evolution of the Seismic Qualification Utility Group Methodology for Assessing Seismic Adequacy of Nuclear Plant Equipment. It should be required reading for regulators so that they both understand the issue and understand what has been done to address it.

Here is a quote from the abstract that should result in a nearly immediate restart of the North Anna nuclear power plant as well as a cessation of a massively expensive, time consuming and unproductive new effort to review and redo work that has already been done before.

SQUG took the lead in developing a cost-effective method of resolution of USI A-46 based on the performance of equipment in actual earthquakes. SQUG sponsored an evaluation of earthquake experience data for eight classes of equipment in non-nuclear facilities. The evaluation, concurred with by the independent expert judgement of the Senior Seismic Review and Advisory Panel (SSRAP), showed that adequately anchored equipment in these classes are inherently rugged under seismic ground motions less than “bounding spectra” having peak ground accelerations of up to about 0.3g. It also demonstrated the feasibility of applying earthquake experience data to verify the seismic ruggedness of certain classes of equipment used in both conventional and nuclear power plants.

The earthquake that briefly shook the North Anna nuclear power station had peak ground accelerations that were twice the recorded “design basis” (0.13 g), but they were still substantially less at 0.26g than the 0.3g at which nuclear plant equipment still displays “inherent ruggedness.”

Even though earthquake science might have advanced considerably in the years since nuclear plants were first being constructed, the engineering principles developed before the precision geophysics were still quite adequate to protect equipment from being vulnerable damage.

As a guy who gained his nuclear knowledge on warships that have been subjected to shock tests, I never understood the concern among the antinuclear industry regarding earthquakes. I wish I could find some unclassified versions of the videos that I have seen of the shock tests. The visual demonstration might convince some of the worriers. It is impressive to see the way that properly secured steel piping flexes and shakes during explosively induced vibrations that are far greater than those experienced during an earthquake and then goes back to its original configuration without damage.

Addendum (Added September 19, 2011) From Howard Shaffer “…the shock warships receive from battle damage is far greater than earthquake shocks, and experience has resulted in designs to withstand these shocks. Nuclear powered warships have been subjected to nearby explosions in tests, to verify these designs. This same technology applies, and is used in nuclear power plants on land. That is why we have such confidence in the plants surviving earthquakes.” End Addendum

Earthquakes happen. Engineers who design nuclear power plants and constructors who build them have always known that fact and have been incentivized to ensure that the plants they design and build will not be damaged by the natural events. More than 50 years worth of nuclear power plant operating history has shown that they have done their job and will continue to do their job. It is time to move on and find a different reason to worry.

Note: This post has been slightly revised with corrections about the details of Howard Shaffer’s visit to Mineral, VA and conversations with people knowledgeable about the plant’s condition following the earthquake.

Updates on the Issue

Reuters – (September 20, 2011)UPDATE 2-Dominion sees Va. North Anna 1 ready for Sept restart