Browns Ferry Nuclear Power Plant Turbine Trip and SCRAM leave station on offsite power

Power ReactorEvent Number: 47299
Facility: BROWNS FERRY
Region: 2 State: AL
Unit: [ ] [ ] [3]
RX Type: [1] GE-4,[2] GE-4,[3] GE-4
NRC Notified By: RAY SWAFFORD
HQ OPS Officer: VINCE KLCO
Notification Date: 09/28/2011
Notification Time: 08:26 [ET]
Event Date: 09/28/2011
Event Time: 04:14 [CDT]
Last Update Date: 09/28/2011
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
Person (Organization):
REBECCA NEASE (R2DO)
UnitSCRAM CodeRX CRITInitial PWRInitial RX ModeCurrent PWRCurrent RX Mode
3A/RY100Power Operation0Hot Shutdown

Event Text

AUTOMATIC REACTOR SCRAM DUE TO A TURBINE TRIP”At 0414 [CDT] on 9/28/2011, the Unit 3 reactor automatically scrammed due to actuation of the Reactor Protection System [RPS] from a turbine trip. Preliminary indications show the turbine tripped on a generator trip with generator neutral overvoltage (359GN) relay actuation. Cause of relay actuation is under investigation. Seven Safely Relief Valves (SRVs) cycled due to the reactor pressure transient with reactor pressure automatically controlled by the Main Turbine Bypass Valves. All systems responded as expected to the turbine trip. No Emergency Core Cooling System (ECCS) or Reactor CoreIsolation Cooling (RCIC) reactor water level initiation set points were reached. Primary containment isolation and initiation signals for groups 2, 3, 6 & 8 were received as expected. Reactor water level is being automatically controlled by the feedwater system.”This event is reportable within 4 hours per 10 CFR 50.72(b)(2)(iv)(B) ‘any event or condition that results in actuation of the RPS when the reactor is critical except when the actuation results from and is part of a pre-planned sequence during testing or reactor operation.’ It is also reportable within 8 hours per 10 CFR 50.72(b)(3)(iv)(A) and requires an LER within 60 days per 10 CFR 50.73(a)(2)(iv)(A).”The NRC Resident Inspector has been notified.”All control rods fully inserted. The plant is being supplied from offsite power and is in a normal shutdown configuration. The MSIVs are open with decay heat being removed via steam to the main condenser using the bypass valves. There was no impact on Units 1 or 2.

The Browns Ferry Nuclear Plant is located on the Tennessee River near Decatur and Athens, Alabama, on the north side (right bank) of Wheeler Lake. The nuclear power plant is named after a ferry that operated at the site until the middle of the 20th century.

The site has three General Electric boiling water reactor (BWR) nuclear generating units and is owned entirely by the Tennessee Valley Authority. Browns Ferry was TVA’s first nuclear power plant; its approval occurred on June 17, 1966 and construction began in September 1966.

In 2006, the Nuclear Regulatory Commission (NRC) renewed the licenses for all three reactors, extending them for an additional twenty years.

The Nuclear Regulatory Commission’s estimate of the risk each year of an earthquake intense enough to cause core damage to the reactor at Browns Ferry was: Reactor 1: 1 in 270,270; Reactors 2 and 3: 1 in 185,185, according to an NRC study published in August 2010.

The Nuclear Regulatory Commission in early May gave the Tennessee Valley Authority a “red” or “high safety significance” rating in connection with last fall’s failure of a cooling-water injection valve at Browns Ferry on the Tennessee River near Athens, Ala.

The NRC said the valve may have been inoperable for more than 18 months at TVA’s oldest nuclear plant. The valve is part of a system that would be used for core cooling during certain accident scenarios, and its inoperable state could have led to core damage had a series of unlikely events occurred. The valve has been replaced.

“Red” is the worst level given by the NRC before a plant is shut down, something the agency has never done.

Last spring, TVA appealed the red rating, saying the problem was a mechanical flaw in the valve. NRC denied the appeal in June, but continued an independent review of TVA’s contention that other utilities might have the same testing and mechanical problems.

In August, NRC reiterated its denial and said TVA had opportunities to find and fix the problem well before the valve failed.

“TVA’s failure [in its method of testing] contributed to the performance deficiency,” states the NRC letter, signed by NRC Regional Administrator Victor M. McCree.

At 5:01 PM on April 27, 2011, all three reactors scrammed due to loss of external power caused by a tornado in the vicinity of the plant. Control rod insertion and cooling procedures operated as designed with no physical damage or release of radiation. Diesel backup generators provided power after a brief period of outage.

An NRC Unusual Event, the lowest level of emergency, was declared due to loss of power exceeding 15 minutes.

Additionally, a small oil leak was found on one generator. Due to widespread transmission grid damage from the storms and because of the shutdown of Browns Ferry, significant blackouts occurred throughout the Southeastern United States.

Source: www.nrc.gov, via Enformable
About author
Enformable is focused on providing critical information about energy related topics for readers around the world.The functional goal of the project is to provide a user-friendly public resource, complete with database of supporting research materials and data.Facebook Twitter
Read More About , , , , , , , ,
Submit your comment

Please enter your name

Your name is required

Please enter a valid email address

An email address is required

Please enter your message

*

Enformable © 2014 All Rights Reserved

More in Featured, Nuclear News
Monju
Japan freezes fast breeder plans at Monju

Monju, Japan’s prototype fast breeder reactor, has had its research budget slashed. This might not come as a big surprise, given the anti-nuke sentiment in Japan and the tattered state of its nuclear...

Close