Browns Ferry restart update

We reported earlier this week that TVA's Browns Ferry Unit 1 nuclear power reactor was restarted after being down more than twenty years. It was shutdown in 1985 when it was discovered that the plant's construction did not match the blueprints. Prior to that, an incident at Browns Ferry in 1975 almost resulted in a "Tennessee Valley Chernobyl" reactor meltdown.

TVA had hoped to have power from the reactor on the grid by late this week. Things didn't quite go as planned. Here's the NRC incident report:

Facility: BROWNS FERRY
Region: 2 State: AL
Unit: [1] [ ] [ ]
Notification Date: 05/24/2007
Notification Time: 04:42 [ET]
Event Date: 05/24/2007
Event Time: 02:11 [CDT]
Emergency Class: NON EMERGENCY
10 CFR Section:
50.72(b)(2)(iv)(B) - RPS ACTUATION - CRITICAL
50.72(b)(3)(iv)(A) - VALID SPECIF SYS ACTUATION

Unit SCRAM Code RX CRIT Initial PWR Initial RX Mode Current PWR Current RX Mode
1 M/R Y 3 Startup 0 Hot Shutdown

Event Text

MANUAL REACTOR SCRAM DUE TO ELECTRO-HYDRAULIC CONTROL (EHC) SYSTEM LEAK

"On 05/24/2007 at 0211 CDT Browns Ferry Unit 1 initiated a Manual reactor SCRAM due to an Electro-Hydraulic Control (EHC) System pressure lowering and reservoir level lowering due to an EHC system leak. The leak was from #6 Main Turbine Combined Intermediate Valve (CIV). All Systems responded as required to the manual SCRAM signal. No Emergency Core Cooling System (ECCS) initiations occurred as a result of the manual SCRAM signal. Reactor water level was maintained in the normal band during the SCRAM. There were no Primary Containment Isolation signals received during the SCRAM. The EHC leak was stopped due to reservoir level depletion and EHC pumps being secured. There were no indications of main steam relief valves (MSRVs) opening. Reactor pressure is being controlled using Main Steam Line Drains. Reactor Level is being maintained in band using Control Rod Drive pumps. Repair of the EHC leak is in progress."

The Scram was characterized as uncomplicated. All rods fully inserted. The only significant equipment out of service at the time was RCIC. When the leak was initially discovered, it was about 60 drops per minute. When repairs were attempted, the piping separated and approximately 600 gallons of EHC fluid was discharged out the break onto the turbine building floor. Cleanup of the EHC fluid is in progress and environmental monitoring is in place to assure no offsite release of the spill.

The licensee notified the NRC Resident Inspector.

SCRAM means "The sudden shutting down of a nuclear reactor, usually by rapid insertion of control rods, either automatically or manually by the reactor operator. May also be called a reactor trip. It is actually an acronym for 'safety control rod axe man,' the worker assigned to insert the emergency rod on the first reactor (the Chicago Pile) in the U.S." (source).

A local news report says two workers were sprayed with the EHC fluid, which is "slightly corrosive but not radioactive," and were taken to a local hospital as a precaution. They were released yesterday afternoon.

According to the article, TVA officials said it was "not a safety problem." A nuclear safety expert with the Union of Concerned Scientists said "It's not until you pressurize the system that you'll find the leaks."

Maybe so. But as we reported here earlier, in April of 2004 the NRC served TVA with notice of a Severity Level III violation at Browns Ferry involving improper welds in the reactor "torus" (a suppression chamber surrounding the reactor as part of its containment system).

In their notice of violation, the NRC says:

Based on the information developed during the inspection, and the information presented at the conference, the NRC has determined that a violation of NRC requirements occurred. The violation is cited in the enclosed Notice of Violation (Notice), and the circumstances surrounding it are described in detail in the subject inspection report. The violation involves four examples of a failure to adhere to the requirements of 10 CFR 50, Appendix B, Criterion V. All four examples were associated with the BF1 Long-Term Torus Integrity Program, and involved: failure to evaluate or incorporate numerous deficient welds into Deficiency Fix Requests sketches; failure to perform numerous repairs on the correct welds; omission of numerous welds requiring repair from Work Orders, and failure of Quality Control (QC) to independently verify the correct location of numerous weld repairs. At the conference, TVA acknowledged the errors, discussed its root cause and extent of condition reviews, and corrective actions.

Given that TVA's Browns Ferry restart has been under intense NRC scrutiny because of past problems there, "It's not until you pressurize the system that you'll find the leaks" (similar to what we used to call the "smoke test" in computers and electronics - plug it in and see if it smokes) may not be the best safety and quality control methodology.

Labels: nuclear power