Update: Arnie Gundersen, a nuclear expert who conducted an audit of Vermont Yankee for the Legislature and who spoke with the unnamed employee in question, confirmed yesterday that the previous radioactive leak from a steam pipe occurred in 2005.
David O’Brien, commissioner of the Department of Public Service, said on Tuesday that a 2005 leak at the Vermont Yankee nuclear power plant is not related to the current tritium leak under investigation.
O’Brien said that a steam pipe leak identified in a statement last week by an unnamed Vermont Yankee employee is not a source of the tritium contamination now found in groundwater monitoring wells, one of which has registered a reading of the radioactive isotope as high as 2.5 million picocuries per liter.
“I’m relieved to determine this doesn’t date back to 2005,” O’Brien said in an interview.
The commissioner said he was not aware of the incident because he said the state nuclear engineer deemed it too minor to bring to his attention.
On Monday, Nuclear Regulatory Commission officials confirmed that a previous leak had occurred, and they revealed to reporters in a telephone conference call that it happened five years ago – not in 2008, as alleged by the worker.
Yesterday, in a one-page letter, John Dreyfus, director of Nuclear Safety Assurance for Entergy, said the leak from 2005 is unrelated to the tritium contamination under investigation. Dreyfus verified the following assertions made by the employee: that the leak occurred in the Advance Off-Gas drain pit, the pipe was not considered to be “buried,” i.e. in direct contact with soil; and the pipe was temporarily repaired.
Entergy responds to leak allegation in writing, Feb. 23, 2010
Last week a Yankee employee told Arnie Gundersen, a nuclear engineer who serves on the Public Oversight Panel, that the leak was unisolateable and that it came from the radioactive steam system two years ago. The employee said the only way to have repaired the leak would have been to shut down the nuclear power plant in Vernon. The worker told Gundersen that “Furmanite,” a sealant, was used to “plug the hole.” Gundersen submitted a letter to the department on Feb. 16, citing the telephone conversation as a matter of record.
Dreyfus wrote that Entergy temporarily repaired the steam pipe in February 2005 and permanently fixed it in October 2005 in a planned refueling shut down.
“The leak we have yet to find, we can’t easily get to,” O’Brien said.
O’Brien said the old leak the worker referred to was minor, amounting to a small pool of liquid from a steam pipe in a contained area near the Advanced Off-Gas system. He said the leak was contained within an internal structure that is below grade, not underground, and that it is “fully accessible.” The pipe was not, he said, in contact with soil.
The level of radiation released, he said, was not above “measurable levels.”
“It’s not something that would have allowed contamination in the general environment,” O’Brien said.
The recent leak of tritiated water is in a different location also near the Advanced Off-Gas system, O’Brien said, and investigators are excavating an area near the building in an effort to find the source of the contamination. According to reports from Vermont Yankee officials, they have dug 11 feet below grade and close enough to the AOG structure that they have had to shore up the building.
“The leak we have yet to find, we can’t easily get to,” O’Brien said.
O’Brien said the state nuclear engineer at the time, Bill Sherman, didn’t make him aware of the problem at the time it occurred because it was a “common incident” and not the only instance of a minor leak at the plant.
The source of the leak, the commissioner said, was a steam pipe in a drain pit area of the Advanced Off-Gas system. He said a bad socket weld allowed steam to escape and allowed condensation to collect as fluid on the floor.
Uldis Vanags, the current state nuclear engineer for the Department of Public Service, reviewed plant reports from 2005 and described the leak in an e-mail to O’Brien as a small stream of steam spraying from a 1-inch carbon steel pipe.
“This leak that occurred is not the leak that is presently being investigated,” Vanags wrote. “We don’t know where the leak is right now, but if it was in the AOG pit area it would be readily visible. The present leak may be in the AOG pipe tunnel which carries many pipes with different functions but includes where the pipe leak of concerns comes from, i.e. the AOG pipe tunnel.”
Vanags said there was no “direct pathway for the steam or condensate to enter the ground outside the building.” Airborne radioactive releases would have been captured by the Advanced Off-Gas ventilation system and carried to the stack for release, according to an e-mail from Sherman.
The leak, Vanags wrote, was not reportable to the department or the Nuclear Regulatory Commission under the memorandum of understanding with Entergy.
What follows is an e-mail string from the Department of Public Service.
From: Vanags, Uldis
Sent: Tuesday, February 23, 2010 11:03 AM
To: O’Brien, David
Subject: 2005 AOG pipe leak
Dave: I investigated the facts behind the allegation concerning the AOG steam leak in 2005. The materials provided to me in this investigation are the Condition Report CR-VTY-2005-00484 discovery date of 02/10/2005. Also I reviewed the Temporary Modification work package to repair the leak (M 2005-002). I also discussed this matter with VY engineers and their Health Physicist.
This was a leak on a 1 inch carbon steal pipe in what is called the drain pit area. The leaking pipe is from a steam line trap that collects condensate (liquid) from a steam pipe in the AOG pipe chase. There is no ground connection here. The leak is the result of a bad socket weld and has a small stream of steam spraying out. This leak that occurred is not the leak that is presently being investigated. We don’t know where the leak is right now, but if it was in the AOG pit area it would be readily visible. The present leak may be in the AOG pipe tunnel which carries many pipes with different functions but includes where the pipe leak of concerns comes from, (i.e. the AOG pipe tunnel).
There is no direct pathway for the steam or condensate to enter the ground outside the building. Vapor from the steam in the air goes through the HVAC system up the stack because the building is kept at negative pressure. Any water on the concrete floor would flow to a sump (if there was enough) or just evaporate and go up the stack also. During repair, a HEPA filter was placed in the room to assure any contaminates are routed to the proper engineered pathways.
This leak was not reportable to NRC and not reportable to DPS under our MOU.
A temporary sealant was used to make the repair (as is typical in the industry), prior to the permanent repair.
Uldis
Uldis Vanags
State Nuclear Engineer
Vermont Department of Public Service
112 State Street
Montpelier, VT 05620-2601
802-828-1784 (office)
email – uldis.vanags@state.vt.us
From: William Sherman
To: Hofmann, Sarah ; Vanags, Uldis
Sent: Tue Feb 23 11:24:04 2010
Subject: RE: 2005 tritium incident
Dear Sarah,
The article reference confuses two occurrences. One is a steam leak that would have resulted in airborne releases. The second is a liquid release that would result in Tritium in groundwater.
In the article, NRC confirms the 2005 event as a steam leak.
I recall that at least twice, and perhaps as many as four times, during my 18 year tenure, VY reported steam leaks with the possibility of accompanying airborne radioactive release from the Advanced Offgas System. These airborne releases would have been captured by the AOG ventilation system and carried to the stack for release. This release path is monitored (although not for Tritium). In my opinion, any small amounts of airborne tritium would have been undetectable and well below any limits. Bill Irwin could confirm. Also, these steam leaks would have resulted in small amounts of leakage through doors or other paths. This would have been too small to measure.
I do not have access to daily records, but I seem to recall one such report in the 2005 timeframe. Sorry I can’t be more definitive.
These reports were not a cause for alarm since any releases were well within limits. VY reported correctly to the NRC. We would have been aware of the report to NRC.
I would stress again that this 2005 release does not appear to be related to the current groundwater question that I think is a new phenomenon.
We have given testimony in numbers of places that these new phenomena occur, and once revealed, are handled pretty well by Entergy.
Hope this is helpful.
Bill
