CHATTANOOGA (AP) – The U.S. Nuclear Regulatory Commission has upheld its finding of a serious safety violation that will require increased inspection activities at the Tennessee Valley Authority‘s Browns Ferrynuclear plant in Alabama.
The NRC responded Tuesday to TVA’s appeal of an earlier NRC finding that a stuck valve discovered in October 2010 and then repaired was a rare red level violation.
TVA nuclear spokesman Ray Golden did not return a Wednesday phone message seeking comment.
Federal regulators have said TVA failed to quickly realize that an old valve on one of two residual heat removal systems on the Unit 1 reactor was stuck shut sometime after March 2009.
Employees at the plant discovered the problem when they tried to use the system to shut down the reactor for refueling. The valve may have been inoperable for more than two years.
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 1974, the time of its initial operation, it was the largest nuclear plant in the world. It was the first nuclear plant in the world to generate more than 1 gigawatt of power.
A number of fire safety violations have been issued over the years.
Countless smaller fires have occurred, with some coming close to endangering the reactor core.
“The agency takes full credit for the grace of God,” George Mulley, who authored several critical reports about lax fire enforcement while chief investigator at the NRC’s office of Inspector General, told ProPublica.
One example, in 2003: The plants operators relied on an employee to trip critical pumps during a fire, even though that would require the worker to endure intense heat, heavy smoke and other hazardous conditions.
Another, in April 2010: Failure to protect critical cables from fire damage.
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.
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.
Unit One is a 1,065 MWe BWR built by General Electric. Construction started on Unit One September 12, 1966 and originally came online on December 20, 1973. It is licensed to operate through December 20, 2033.
However, Unit One was shut down for a year after a fire in 1975 damaged the unit.
The March 22, 1975 fire started when a worker using a candle to search for air leaks accidentally set a temporary cable seal on fire.
[quote]A U.S. Nuclear Regulatory Commission bulletin explained the circumstances of the fire.
The fire started in the cable spreading room at a cable penetration through the wall between the cable spreading room and the reactor building for Unit 1.
Site personnel were resealing the penetration after cable installation and were checking the airflow through a temporary seal with a candle flame prior to installing the permanent sealing material. The temporary sealing material was highly combustible, and caught fire.
Efforts were made by the workers to extinguish the fire at its origin, but they apparently did not recognize that the fire, under the influence of the draft through the penetration, was spreading on the reactor building side of the wall.
The extent of the fire in the cable spreading room was limited to a few feet from the penetration; however, the presence of the fire on the other side of the wall from the point of ignition was not recognized until significant damage to cables related to the control of Units 1 and 2 had occurred.[/quote]
This later resulted in the Nuclear Regulatory Commission making significant additions to the standards for fire protection through the publication of 10CFR50.48 and Appendix R. According to the Nuclear Information and Resource Service, the newly-restarted Unit One does not comply with these standards.
Starting in 2002, TVA undertook an effort to restore Unit One to operational status, spending $1.8 billion to do so. The United States Nuclear Regulatory Commission (NRC) approved the restart of Unit 1 on May 15, 2007 and the reactor was brought up to criticality on May 22 for the first time since March 3, 1985.
During initial testing after restart, on May 24, 2007, a leaky hydraulic control pipe in the turbine hall burst, spilling about 600 gallons of non-radioactive fluid, and the newly restarted reactor was temporarily powered down.
Beginning in 2005 Unit 2 was loaded with BLEU (Blended Low Enriched Uranium) recovered by the DOE from weapons programs. This fuel contains quantities of U-236 and other contaminants because it was made from reprocessed fuel from weapons program reactors and therefore has slightly different characteristics when used in a reactor as compared to fresh uranium fuel. By making use of this fuel which would otherwise have been disposed of as waste the TVA is saving millions of dollars in fuel costs and accumulating a database of recycled uranium reactions in LWR use
In a 2005 analysis of significant nuclear safety occurrences in the US, the NRC concluded that the fire at Browns Ferry was the most likely (excluding the actual accident at TMI) “precursor” incident to have led to a nuclear accident in the event of a subsequent failure