Fission Fiction – or how David Lochbaum got it wrong
On August 24th, Mr. Lochbaum posted a story on the Union of Concerned Scientists website about an event in 1988, then proceeded to link it to a 2005 event at a different plant and makes the case that the nuclear industry is filled with screw-ups and near misses. You can read the original article here. As it happens, my career has included learning about these particular events and leading the team that developed some of the solutions that are currently in place to prevent/mitigate the effect. From that, I can say – Mr. Lochbaum got it wrong.
Mr. Lochbaum has done a reasonably good job of regurgitating the publicly available information about the event at LaSalle. Basically, a pump trip caused the reactor to move down in power and flow to a point of natural circulation at high power. In this region under specific circumstances, BWR’s can become unstable and begin power oscillations. The major thing to note was that the safety systems worked WITHOUT operator intervention. Once the power oscillations reached 118% of power, the reactor automatically shut down without human intervention. No fuel failed, let alone radiation released to the public.
That said, the NRC and the industry were rightfully concerned that perhaps, under different circumstances, fuel might have failed and that more robust actions should be taken by the industry to provide greater assurance that reactor cores will not experience such oscillations or that they will be shutdown while the peak power levels remain much lower to eliminate the risk of fuel failure.
The NRC generated some interim operating conditions for all nuclear power plants to avoid operating near the power flow points that might cause such oscillations to occur. They also demanded that the industry come up with a more robust long term action plan. The industry through the Boiling Water Reactor Owner’s Group (BWROG) and with GE as the main technical contractor embarked on a mission to understand the phenomena and determine effective solutions for all types of BWR plants operating in the fleet.
This is the point where Mr. Lochbaum ends his narrative and leaps to events in 2005 at Perry, incorrectly concluding that Perry Operators made the exact same mistakes that LaSalle operators had made in 1988. In reality, the BWROG came up, as requested by the NRC, with two basic approaches.
- Prevention – regional exclusion with protection actions Called Option I
- Detection and Suppression – which uses in core sensors to detect potential oscillations and to shut the reactor down. Called Option III
For the curious Option II was limited to a few older plants with unique sensing systems.
The relevant documents are available on the NRC’s website.
NEDO-31960 – Long-Term Stability Solutions Licensing Methodology – submitted to the NRC 5/1991
GL94-02 – Long-Term Solutions And Upgrade Of Interim Operating Recommendations For Thermal- Hydraulic Instabilities In Boiling Water Reactors – issued by the NRC – issued by the NRC 7/1994
FirstEnergy chose Option III at Perry and in 2001 submitted a revision to their technical specifications to allow use of this methodology. In this approach, the sensing equipment (called OPRMs) provide data to a simple analytical method, once certain conditions are met that appear to be an oscillation mode, the signal to trip the reactor and drive all control rods to full in positions is actuated.
What does all that mean?
It means that Mr. Lochbaum’s accusations regarding the inadequate actions taken at Perry are deceptive and incorrect.
Mr. Lochbaum leaps to two events that occurred at Perry Nuclear power station in late 2004/early 2005. Careful reading of the NRC document describing its concerns related to this event (ML050830113 on the NRC website) shows that on page 27, the NRC acknowledges that Perry’s Option III system worked AS DESIGNED. The NRC’s issues with Perry revolved around the repeated issues with the recirculation pump trips and NOT the potential stability concern.
I suggest that the Union of Concerned Scientists make a more careful review of the facts on the ground before making unfounded allegations regarding the plant safety and performance of the US nuclear industry.