March 21, 2019 DNFSB letter & report – linked here
“Conclusions. As part of the 10-year assessment of the DAF seismic hazard, the previous site contractor, NSTec, analyzed the seismic hazard in 2007 using a PSHA approach. The 2007 PSHA found that the ground motion response spectra significantly exceeded the design-basis earthquake response spectra when compared to the previous analysis completed in 1995. Due to issues with the SASSI code, DAF contractors did not complete the SSI analysis. The Board’s staff review team is concerned that DAF continues to operate with the increase in seismic hazard and MSTS has not adequately evaluated credited safety-related SSCs to ensure that they can perform their safety function during and after a seismic event. Seismic accident scenarios at DAF could result in significant consequences to the offsite public. Since the impact of seismic events on DAF SSCs has not been adequately characterized, DAF continues to operate with unknown risk.”
photo: Device Assembly Facility (DAF) at NDOE’s Nevada National Secuirty Site northwest of Las Vegas, NV