Diablo Canyon Still Awaits Sufficient Tests
On Tuesday, San Luis Obispo County will be reviewing a resolution to support PG&E’s 20-year extension of its operating license for the Diablo Canyon nuclear power plant. Bruce Severance, a member of the Diablo Canyon Decommissioning Engagement Panel, sent a letter contesting the approval.
As a member of Diablo Canyon Decommissioning Engagement Panel (DCDEP), for the past two years I have taken an independent interest in reading PG&E and NRC (Nuclear Regulatory Commission) correspondence going back 30 years, which has led me to support continued operation of Unit 2 at DCPP for 10 years, and I oppose continued operation or further investment of ratepayer funds in repairs to Unit 1. This view is mine, and I do not write on behalf of the panel.
I know there is strong support for continued operation of Unit 1 for local economic reasons but there are strong economic reasons to view it as a bad investment for ratepayers and the state:
(1) PG&E’s 2006 embrittlement analysis submitted to the NRC and based on their own prior stress tests (1986, 1992, and 2003) suggested that Unit 1 would be within 3 percent of the maximum embrittlement allowed under NRC “screening limits” for “pressurized thermal shock,” a condition in which a coolant leak could lead to too much cold water added relative to the temperature and pressures within the reactor vessel before a safe shutdown could occur.
One engineering parameter for measuring embrittlement is called the RT-PST (reference temperature for pressurized thermal shock). The NRC’s own analysis confirmed PG&E’s calculation that Unit 1 would reach this maximum embrittlement threshold around 2025 (within 3 percent of maximum RT-PTS of 270F. value by Nov. 2024). An NRC letter of approval of a 37-month operational license extension dated July 17, 2006, clearly shows the NRC confirming the trajectory of Unit 1 embrittlement by 2025. I am happy to provide the full 7-page approval letter, which also required an additional embrittlement stress test by 2009 as a condition of the extension that was NEVER performed.
(2) Please note, Unit 1 was known to have metallurgical “flaws” at the time it was delivered, when Westinghouse admitted there were high amounts of impurities in the reactor pressure vessel welds that would predispose the reactor to premature failure. It is therefore not surprising that the pre-2004 stress test results (coupon test data) are consistent with mathematical projections based on those impurities.
(3) In violation of NRC rules and mathematical procedures, PG&E has moved to judge all of its pre-2004 stress test data as “not credible” to replace it with a mathematical extrapolation method that integrates data from “sister” plants. The only sister plant in operation today that used the same impure weld material is Palisades. In NRC’s written responses to public inquiry, Palisades and DCPP 1 are both stated to be among the four most embrittled reactors in the U.S. by the NRC’s 2013 published comments.
(4) Although the former NRC official hired by the DCISC (Diablo Canyon Independent Safety Committee) to investigate Unit 1 embrittlement has defended the 2011 Westinghouse PTS Evaluation, M. Kirk admitted that the other key embrittlement parameter measured in stress testing, USE (upper shelf energy), will be reaching the maximum screening limits by 2029 and will reach that limit sooner if it is not operated at 85 percent capacity. So by endorsing the 2011 Westinghouse Report, Dr. Kirk is contradicting his own calculations, claiming that Unit 1 may be too severely embrittled to operate at full power until 2029, but also endorsing its operation at full power until 2044.
(5) Although Kirk suggests further testing is needed, the DCISC seems content to wait until 2028 for those test results. Alternative test methods are available that would allow us to have embrittlement stress test data (hard science compared to mathematical extrapolations), but neither PG&E nor the DCISC see a need to do that, despite the fact that all of the RT-PTS data we have (pre-2004 data) indicates maximum embrittlement will be reached by 2026 — at the latest.
(6) PG&E has postponed additional testing about five times since 2009 and is now 15 years late (as per the conditions of approval of the last 2006 extension), and for this reason, there is a great deal of uncertainty around the actual condition of the Unit 1 reactor pressure vessel (RPV). (See NRC 2006 amendment to “surveillance program” requiring that Capsule B be tested at 20.7 effective full-power years, approx. 2009). At the time, the NRC recognized Unit 1 would reach its maximum embrittlement or “screening limits” by 2025-2026 at the latest. Additional testing is critical. Although alternative test methodologies exist that would allow us to retest stress test samples that are already in archives, PG&E and the DCISC are resisting further testing using these alternative means, even though their hired expert to assess embrittlement recommends it. There is simply NO REASONABLE EXCUSE TO DENY THE PUBLIC AND OUR ECONOMIC PROSPERITY THE RIGHT TO ADDITIONAL TEST DATA IMMEDIATELY.
(7) The NRC will not rule on the license extension for either reactor at Diablo Canyon for at least three years. They normally have a four-year review period. From the standpoint of NRC approval, the motion by the Board of Supervisors preempts the NRC review process.
(8) State Senator John Laird sent a letter to the Board of Supervisors last week stating that this vote to approve a 20-year extension of both units at DCPP is outside the scope of SB846 which calls for a five-year extension, and premature because it is being forced before rulings by the NRC, the DCISC, and state agencies.
(9) To tell all sides of the story, there are NRC rules to allow “safe” operation of severely embrittled reactors (under 10 CFR 50.61a) however, these require special operating conditions, a higher cost of operation, etc. and the state deserves to have a clear determination about whether Unit 1 is worthy of significant financial risk to the state — independent of the safety issues. So even if the DCISC rules in favor of endorsing the Kirk and 2011 Westinghouse embrittlement analyses saying everything should be fine until 2044, approval of the evaluation by the NRC would allow continued operation at full power and without the usual mitigations required of a severely embrittled reactor.
The question is not simply one of safety: Is this a good deal economically for the state, the taxpayers, and for us as ratepayers to invest in a severely embrittled reactor that would require hundreds of millions to operate safely and for which replacement of the RPV is currently not being discussed? SB846 requires PG&E to disclose to the state any characteristic flaws or maintenance issues that would jeopardize its investment in continued operation, and failure to disclose such issues is the one condition that could trigger a repayment requirement. (Debt is no longer forgivable.) For this reason, PG&E also has a fiduciary duty to its shareholders to assure THEM that they are not banking on a risky investment.
(10) SB846 requires that the CEC evaluate other possible generation alternatives if DCPP doesn’t look like a good investment. The cost trade-offs are supposed to be evaluated. How can we endorse this at the Board of Supervisors level when every critical input for that decision is still unavailable?
For all of the above reasons, I request that you REQUIRE further testing of the pre-2004 test samples already in hand using the micro-CT or micro-Charpy test methodologies suggested by the DCISC’s hired expert, and that this testing be performed before any county action to endorse or affirm official support of continued operation for a five-year period, and that vote should not occur until after the state has made its final decision on continued operation. Endorsement of 20-year operation should wait for NRC approval.