Lori Dengler | Humboldt Bay Nuclear Power Plant: A Geological Saga – Times Standard

The Nuclear Regulatory Commission is in the process of accepting PG & E’s application to terminate the license for the Humboldt Bay Nuclear Power Plant, Block # 3. It was foreseeable for a long time.

The nuclear facility ceased operations for maintenance and refueling in 1976. It never produced electricity again and in 1983 PG&E decided to shut down the reactor for good. Dismantling began in 2009 and unused fuel rods, spent fuel and contaminated parts of the facility were buried in containers and buried on the site.

Here is the naked story of Block # 3: planning in the late 1950s, groundbreaking in January 1961, commissioning in August 1963, closure in July 1976, PG&E notice of final closure in 1983, a permit for waste storage on the Terrain 1988 and active decommissioning and waste disposal 2009-2018. But there are many stories between these points, and the geological crosses some of the greatest milestones in geosciences.

Nuclear power was seen as the solution to energy needs in the 1950s. PG&E looked at three potential locations: Point Arena, Bodega Bay and Humboldt. The proximity to the San Andreas Fault and the outcry from local activists at the time struck the first two off the list and moved on to the Humboldt Bay area.

How could they build a reactor in one of the most seismically active areas of the contiguous 48 states and just a few miles above the only US fault outside of Alaska that can cause an M9 earthquake? The simple answer is what they didn’t know; they had no idea that such a large earthquake could occur.

Turn the clock back to 1958. No global seismic network. There is a patchwork of regional seismic networks around the world, but it will take the underground nuclear test ban treaty to advance the creation of a global network, and another five years before the ring of fire and global earthquake concentrations become clear.

1958 is before plate tectonics. Many geologists still consider the planet’s surface to be relatively static. They understand a lot about geological processes, but few accept the dynamic planetary surface that is widely known today. Wegener proposed continental drift in 1912 but focused only on the spread and splitting of continents and not on the earthquake potential. Few scientists accepted it in the 1950s. The term “subduction zone” will not appear for another five years, and the Cascadia subduction zone will not be fully recognized for another thirty years.

In 1958, there were only two seismic stations on the north coast – one at HSU and one a few miles away on Fickle Hill – that were insufficient to regionally detect small earthquakes or pinpoint larger ones. The Berkeley seismic catalog showed no significant earthquake activity near the power plant location. Large earthquakes in 1932 and 1954 are known, but the epicentres were poorly located and were not viewed as a threat to the location.

The discipline of paleoseismology did not yet exist in 1958. There is only half a century of recorded seismic data and older written reports on which to base an earthquake catalog. Techniques for identifying and dating prehistoric earthquakes and potentially active earthquake faults are still a decade away. There are also no environmental impact studies.

In 1958, earthquake engineering is a young discipline. There is no strong exercise program and almost no buildings are instrumented in such a way that they understand how buildings react to strong vibrations.

In the first few years after Unit # 3 went online, dozens of articles were published on the new theory of plate tectonics and the expansion of the sea floor. Magnetic mappings off the coast from Northern California to British Columbia show the characteristic fingerprint of a dispersal center and a subduction zone. The subduction zone is not initially of concern – it is small and there have been no known earthquakes.

In 1971 the M6.6 San Fernando earthquake changed the earthquake hazard landscape. The earthquake killed 64 people and the biggest failure was the Veterans Hospital in Sylmar, where two buildings collapsed and 49 people died. The failures were caused in part by its proximity to surface faults, and in 1973 California passed laws restricting construction in fault zones.

The Atomic Energy Commission also became aware of this and asked all operating nuclear power plants to check the vibration potential of their locations and to identify possible sources of surface faults. PG&E commissioned TERA Corporation to set up the first network of seismic stations in the Humboldt Bay region.

In 1974 the Humboldt Bay Seismic Network went into operation and would provide the first detailed insight into earthquake activity on the north coast over the next 12 years. Bob McPherson, who years later became my first PhD student, helped build the network and ran it from 1975 until it closed. It wasn’t long before a major quake struck. On June 7, 1975, an M5.6 eq occurred near Fortuna. The earthquake was strong enough to topple items off shelves and create cracks in the sidewalk. It gave added urgency to the concern about the power plant 16 miles north.

So began the geological survey of the north coast. Unit # 3 was an unexpected blessing for geologists. The seismic network was only the first step. Years later, PG&E hired Woodward Clyde (now URS) consultants to investigate the potential for surface defects and provide the detailed analysis that an environmental impact study should now routinely uncover. Even after the decision to finally shut down the reactor, investigations into the storage area and the tsunami potential continued.

The saga of # 3 reminds me of what Donald Rumsfeld (DOD Secretary) said in 2002: “… But there are also unknown strangers – those we don’t know, those we don’t know.” Ah yes, those unknown strangers. So much that we didn’t know when the system was planned and built and which were important to know in retrospect. I’m just beginning to scratch the surface of the geological history of nuclear power on the north coast. More next week.

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