Diablo Canyon Nuclear Plant Unit 1’s reactor vessel was built with faulty material, so it’s vulnerable to embrittlement. An embrittled reactor vessel can shatter like glass and cause a catastrophic meltdown. Despite this, PG&E has not tested for embrittlement for over 20 years.
PG&E has now committed to removing Capsule B from Unit 1 to test for embrittlement during the upcoming April outage. Previous attempts to remove this capsule have been unsuccessful.
On March 18, 2025, Mothers for Peace sent a letter to the CEO of PG&E, Patti Poppe, setting forth its expectation that Capsule B will finally be removed during this upcoming April outage and subsequently tested for embrittlement so we will learn if it’s safe to operate.
We are compelled to send this letter because of previous failures by PG&E to test the Diablo Canyon Nuclear Plant for embrittlement. We agree with the 9th Circuit Court of Appeals when they state:
We share Petitioners’ concerns about the public health and safety implications of repeatedly postponing Capsule B’s withdrawal. It has been about two decades since PG&E withdrew and tested a surveillance capsule from the Unit 1 reactor vessel—and even longer since a surveillance capsule withdrawn from Unit 1 generated credible data. Although Unit 1’s operating license has now officially expired, the reactor continues to operate under the NRC’s “timely 10 renewal” rule because PG&E has submitted a license renewal application. San Luis Obispo Mothers for Peace, 100 F.4th at 1056–58 (citing 10 C.F.R. § 2.109(b)). Capsule B remains a key source of data for the license renewal period. Under the current schedule, PG&E is slated to remove Capsule B in the spring of 2025 and use it to inform the company’s pending license renewal application for Unit 1. Any further delay in Capsule B’s withdrawal will mean that PG&E lacks a critical data source about the future integrity of the reactor vessel, without which a future license renewal may be subject to legal challenge.
San Luis Obispo Mothers for Peace v. NRC, 2025 U.S. App. LEXIS 1104 at *10 (9th Cir.) January 17, 2025
Background: Read about the Mothers for Peace brief filed in March 2024.