, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,

It has been known that Brunswick Nuclear Power Station’s Design Basis storm surge-flood level was too low in the event of a severe hurricane since at least 1992. The NRC and the utility have continued to ignore this fact. In 1992 NOAA found “that a severe hurricane could induce a surge elevation of 28.4 ft MSL at the BNP site, or 6.4 ft above the plant’s design basis flood level.” Apparently not liking the result, the NRC got the Army Corps of Engineers to do a study, based on assumptions of a hurricane with far from the maximum possible winds. Already in 1969 Hurricane Camille had made US landfall with sustained winds of 190 mph. However the Army Corps study assumes a hurricane with 128 mph winds at the site. There are, of course, additional factors in storm surge: https://miningawareness.wordpress.com/2018/09/14/introduction-to-storm-surges/

More recently it has been concluded by the US NRC that the elevation needs to be up to 33.8 ft. However, it remains at 22 ft, reportedly with 4 ft “cliff edge” barriers to seal doors. https://miningawareness.wordpress.com/2018/09/13/brunswick-nuclear-power-stations-cliff-edge-barriers-appear-to-fall-almost-8-feet-short-of-required-storm-surge-protection-level/

According to the Army Corps study, commissioned for the NRC: “In 1992, NOAA published a study entitled “A Storm Surge Atlas for the Myrtle Beach, South Carolina, and Wilmington, North Carolina, Area” that delineates limits of inundation caused by hurricane-induced flooding in the subject area. This study found that a severe hurricane could induce a surge elevation of 28.4 ft MSL at the BNP site, or 6.4 ft above the plant’s design basis flood level.” (p. 46)

For approximating the SPH, Hurricane Hazel was selected because this event was similar in trajectory and speed to the hypothetical SPH…” (p. 48)

Results of the present analysis show that the design basis flood level at which the BNP was constructed is adequate to ensure that safety margins protecting against extreme hurricane-induced storm-surge flooding are maintained. The EST analysis predicted that a 2,000-year return period event induces a total surge (combined storm surge, wave setup, and tide) elevation of 16 to 17 ft MSL. This elevation is 5 ft lower than the 22-ft design basis flood elevation, which was computed using the PMH. (The PMH is estimated to produce a total surge level that has a return period of 2,000 years and is the basis for defining the design basis flood elevation.)

This analysis also indicates that a total surge level of 22 ft MSL has a return period of approximately 100,000 years (which is the design elevation of the BNP).” (p. 51)
(See chart of p. 49 of Army Corps Study for wind speed, etc.) “Development of Water-Surface Elevation Frequency-of-Occurrence Relationships for the Brunswick, North Carolina, Nuclear Power Plant Site” by Norman W. Scheffner, David J. Mark, Lihwa Lin, Willie A. Brandon, Martin C. Miller Technical Report CHL-99-12 December 1999 http://www.dtic.mil/dtic/tr/fulltext/u2/a372183.pdf

The so-called cliff edge barriers are essentially the original design basis of 22 ft with 3.6 ft. of wave run-up barriers and a small margin!



Related links:
The average diameter of hurricane-force winds is 100 miles...”