Defense in Depth Part I: A War for Safety

Thomas Wellock
Historian

One hundred years ago the French and German armies of World War I devised a new defensive strategy called “defense in depth.” Its aim was to prevent an enemy breakthrough of an army’s frontline with a deep system of interconnected trench lines and strong points.

Defense in depth circa WWI. Photo courtesy of the Library of Congress
Defense in depth circa WWI. Photo courtesy of the Library of Congress

Popularized in all its desperation and grisly effectiveness in films such as All Quiet on the Western Front, defense in depth has become the NRC’s official metaphor in the battle to protect the public from radiation hazards. It is the key concept governing nuclear safety in using multiple strategies in safety-system design, operations, and emergency procedures and planning.

The NRC’s use of the term has roots in the Manhattan Project of World War II. Military metaphors seemed particularly apt for those charged with ensuring the safety of the early plutonium production reactors at Hanford, Washington. They worried about the potential for a reactor “catastrophe” from a radiation release of “explosive violence.” Their solution was to erect multiple “lines of defense” of trained operators and emergency personnel, carefully sealed fuel rods, shielding walls, backup cooling and power systems, and even a backup to the backup shutdown system—a final solution so drastic that it would destroy the reactor to save the operators lives. Fittingly, its moniker derived from another military term — the “last ditch” safety device.

After the war, the “lines of defense” in reactor safety were categorized into functions by Atomic Energy Commission safety committees:

  1. Features that made a reactor inherently safe;
  2. “Static,” or physical, barriers, such as containment buildings, were to halt the escape of radiation; and
  3. Active systems were to shut down and cool the reactor in the case of unusual conditions.

While the AEC’s safety approach became more coherent, there was no consensus among experts over the relative importance of each category. Some experts focused mostly on a design’s physical barriers, while others gave weight to all three categories and included reactor operation too.

Over time, “defense in depth” replaced the scattered concept of “lines of defense.” Its first use appears to have been in 1958 to describe safety design in the plutonium extraction processes at Hanford. In a 1965 letter to Congress, AEC Chairman Glenn Seaborg applied the term to civilian reactor safety as an accident prevention and mitigating strategy.

It provided, he wrote, “multiple safeguards against the occurrence of a serious accident, and for containment of fission product release.” The term stuck.

But the story continues. The Office of Nuclear Regulatory Research has published a report on the history of defense in depth up to the present, which covers the term’s application to the whole nuclear fuel cycle. It’s a fascinating look at how this bedrock safety concept has evolved under the influence of events and new knowledge. We’ll have more on this report on Wednesday.

 

 

Enhancing NRC Public Meetings

Lance Rakovan
Senior Communications Specialist

pubmeetingIPThe NRC holds a lot of public meetings – more than 1,000 a year. Sometimes we seem to hit the mark with stakeholders. Sometimes not so much. In any event, we are always looking to make our meetings better. I recently co-chaired a group of NRC staff members who were tasked with providing the agency’s Executive Director for Operations (EDO) with a list of recommendations to make our public meetings better.

We took a comprehensive look at the NRC’s public meeting policies, processes, and guidance, including their implementation, and made recommendations to improve those aspects of our work. The group provided its report to the EDO earlier this year (ML15029A456).

Who was part of the group? The group’s members included representatives of the two offices that conduct by far the most NRC public meetings (the offices of Nuclear Reactor Regulation and New Reactors); members from all four NRC regions, including a public affairs officer; and many others. The task group members brought to the table extensive public meeting experience.

The task group considered additional public input provided through sources such as:

  • Years’ worth of feedback received through the NRC’s Public Meeting Feedback Form;
  • The results of extensive public outreach- and meeting-related interviews and surveys involving the San Onofre Nuclear Generating Station; and
  • Input received during previous public meetings addressing public involvement.

This information was instrumental in the task group’s work and informed decisions the group made.

Now that the report is done, what are the next steps? NRC staff members are currently creating and revising our policies and guidance, including our policy statement on public meetings. Our intent is to engage the public by sharing draft products for comment and holding a public meeting once some of the improvements recommended by the task group have been made.

We hope that you will participate in those activities and continue to provide your input through the Public Meeting Feedback Form (fill out a hard copy at a meeting or provide your input electronically by clicking on “meeting feedback form” for meetings on the public meeting schedule) as well as through discussions with NRC staff. Our goal is to provide the public with useful information on our activities and to conduct business in an open manner, while at the same time ensuring that we can carry out our mission.

As the agency takes action on the recommendations, we’ll update you via the blog on proposed improvements, progress we’re making, and how the public can be involved with initiatives.