Photo courtesy of Energy Northwest
Solution

Columbia Generating Station, Seismic Probabilistic Risk Assessment

Richland, WA

Market: Nuclear

Completion

2019
Columbia Generating Station

Photo by SGH with permission from Energy Northwest

After the Fukushima Daiichi accident, the U.S. Nuclear Regulatory Commission (NRC) issued 10 CFR 50.54(f), a letter requiring licensees to perform a re-evaluation of seismic hazard and take further actions if it exceeds their design basis. In response to this letter, Columbia Generating Station (CGS) performed a seismic probabilistic risk assessment (SPRA) of their facility.

Scope | Solutions

CGS has a one-unit boiling water reactor with a Mark II containment design. Essential safety and FLEX system components are located in several buildings and the yard. CGS is a deep soil site with significant soil-structure interaction (SSI) effects on building seismic responses. SGH performed the seismic fragility scope of the CGS SPRA and highlights of our work include the following:

  • Performing seismic walkdowns and building an electronic database of results

  • Selecting reference earthquake ground motion and acceleration time histories

  • Generating probability distributions of in-structure responses by Latin hypercube sampling

  • Developing thirty randomized finite element models for structures

  • Selecting thirty representative soil profiles from 4,800 site simulations

  • Simulating SSI/SSSI responses using efficient hybrid computational methods

  • Developing novel methods for fragility evaluation to address unique conditions

  • Efficiently estimating more than 1,000 CGS-specific representative fragilities for risk ranking and prioritization of detailed evaluations

  • Developing a new approach for hybrid fragilities that improves on EPRI 1025287

  • Evaluating failure modes from building impacts and separations

  • Modeling partial correlation between major structure fragilities

  • Evaluating and screening non-vibratory hazards and upstream dam breaches

  • Supporting the CGS SPRA submittal to the USNRC

Project Contact(s)