On Thursday, April 7, STP filed a License Amendment Request (LAR) with the Nuclear Regulatory Commission (NRC) to permanently change the Unit 1 Technical Specifications to operate without Shutdown Bank Control Rod D6. Prior to the submittal, internal and independent third party reviews – including USA partners Comanche Peak — were completed.

While preparing to restart following a scheduled refueling outage — 1RE19 — late last year, Control Rod D6 could not be reliably withdrawn during startup testing. All other 56 Controls Rods in Unit 1 operated as expected. A detailed inspection of the D6 Control Rod Drive Mechanism (CRDMs) uncovered that a deformed rod holdout ring was the cause of the D6 performance issues. Thorough testing and inspections of the other 56 CRDMs in Unit 1 confirmed that the failure is isolated to Control Rod D6.

In early December, an Emergency License Amendment request to revise STP Technical Specifications 5.3.2 to operate Unit 1 with 56 full-length control rods instead of 57 was submitted to the NRC. The NRC approved the License Amendment on Dec. 11, 2015, for the current 18-month operating cycle. The amendment supports Unit 1 operations with Shutdown Bank Control Rod D6 and drive shaft removed. This amendment expires in March 2017.

Since that time, multiple options have been evaluated to determine a long-term, permanent solution that supports continue safe, reliable operations. Following a review of the options, a decision was made to submit an LAR that supports a permanent change to the design and licensing basis of Unit 1 to operate with 56 control rods. Detailed analyses demonstrate that appropriate shutdown margins are maintained with this configuration.

“This is the prudent and right decision from both a safety and reliability standpoint,” said Senior Vice President Dave Rencurrel, who serves as the executive sponsor of the D6 Project Team. “Our team has done an outstanding job in the development of the LAR. Our goal is to have the Unit 1 LAR approved prior to the start of 1RE20 next spring.

“We are confident that the path forward that ensures both safety and protection of the asset is a permanent change to the design and licensing basis of Unit 1 to operate with 56 control rods instead of 57.”

Prior to the LAR submittal, STP met with NRC staff in early March providing a summary of our path forward and justification to maintaining the safe operation of Unit 1 with no control rod in core location D6. The NRC process will include a thorough regulatory review and opportunities for public interaction.

The next major milestone will be the NRC to make a determination, within the next 45 days, that the LAR is technically adequate for review.