ML20203J832
| ML20203J832 | |
| Person / Time | |
|---|---|
| Issue date: | 02/25/1998 |
| From: | Marsh L NRC (Affiliation Not Assigned) |
| To: | Lochbaum D UNION OF CONCERNED SCIENTISTS |
| References | |
| NUDOCS 9803040319 | |
| Download: ML20203J832 (3) | |
Text
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i-February 25, 1998 L-p; o Mr. David A. Lochbaum
- Union of Concerned Scientists 1616 P Street NW, Suite 310 Washington, D.C. 20036
Dear Mr. Lochbaum:
On September 10,1997, the Nuclear Regulatory Commission (NRC) staff met with you and Mr. Paul Gunter of the Nuclear Information Resource Service to discuss fire barrier penetration seals at nuclear power plants. In the enclosure to a letter of November 21,1997, Mr. John i
Stolz provided a list of follow-up items that resulted from our meeting with you and Mr. Gunter.
Items five and six from this list were questions based on an NRC Office of Investigations (01) interview of Mr. Hitoshi Takahashi, a Dow Corning Corporation employee. The interview discussed several aspects of silicone foam fire barrier penetration seat material.
The staff reviewed these two issues and spoke to Mr. Takahashi, and Ms. Lynn Krause, also of Dow Corning, on January 23,1998, via teleconference. A summary of this teleconference is i
enclosed. Based on its review, including the information obtained from Mr. Takahashi, the staff has closed items five and six, and no further action is planned. I have provided this information to Mr. Gunter under separate cover. If you have any questions regarding this information, l
please contact Steven West (301415-1220) or Chris Bajwa (301-415-1237).
Sincerely, Ledyard B. Marsh, Chief Plant Systems Branch Division of Systems Safety and Analysis Office of Nuclear Reactor Regulation
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Enclosure:
As stated DISTRIBUTION
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Mr. David A. Lochbaum Union of Concerned Scientists 1616 P Street NW, Suite 310 Washington, D.C. 20036
Dear Mr. Lochbaum:
On September 10,1 7, the Nuclear Regulatory Commission (NRC) staff met wit. you and Mr.
Paul Gunter of the Nu ear Information Resource Service to discuss fire barrier netration seals at nuclear power nts. In the enclosure to a letter of November 21,199, Mr. John Stolz provided a list of fol w-up items that resulted from our meeting with yo/and Mr. Gunter, items five and six from this t were questions based on ari NRC Office of vestigations (01) interview of Mr. Hitoshi Taka shi, a Dow Corning Corporation employe The interview discussed several aspects of si cone foam fire barrier penetration seal aterial.
I The staff reviewed these two issu and spoke to Mr. Takahashi, a Ms. Lynn Krause, also of Dow Corning, an January 23,1998, la teleconference. A surnm of this teleconference is enclosed. Based on its review, inclu g the information obtsin d from Mr. Takahashi, the staff
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has closed items five and six, and no f her action is planned. I have provided this information to Mr. Gunter unJer separate cover, if y u have any quest ns regarding this information, please contact Steven West (301-415-12 or Chris Baj a (301-415-1237).
S' cerely, L dyard B. Marsh, Chief PI t Systems Branch Divi 'on of Systems Safety and Analysis Offic of Nuclear Reactor Regulation
Enclosure:
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WASHINGTON, D.C. 20666-0001
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February 25, 1998 Mr. David A. Lochbaum Union of Concemed Scientists, 1616 P Street NW, Suite 310 Washington, D.C. 20036
Dear Mr. Lochbaum:
On September 10,1997, the Nuclear Regulatory Commission (NRC) staff met with you and Mr. Paul Gunter of the Nuclear Information Resource Service to discuss fire barrier penetration seals at nuclear power plants. In the enclosure to a letter of November 21,1997, Mr. John Stolz provided a list of follow-up items that resulted from our meeting with you and Mr. Gunter.
Items five and six from this list were questions based on an NRC Office of Investigations (01) interview of Mr. Hitoshi Takahashi, a Dow Corning Corporation employet The interview discussea several aspects of silicone foam fire barrier penetration seat material.
The staff reviewed these two issues and spoke to Mr. Takahashi, and Ms. Lynn Krause, also of Dow Corning, on January 23,1998, via teleconference. A summary of this teleconference is enclosed. Based on its review, including the information obtained from Mr. Takahashi, the staff i
has closed items five and six, and no further action is planned. I have provided this information to Mr. Gunter under separate cover. If you have any questions regarding this information, please contact Steven West (301-415-1220) or Chris Bajwa (301-415-1237).
Sincerely, W
Ledyard B. Marsh, Chief Plant Systems Branch Div5 ion of Systems Safety nd Analysis Office of Nuclear Reactor Regulation-
Enclosure:
As stated
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UNITED STATES ENCLOSURE g
j NUCLEAR REGULATORY COMMISSION o
f WASHINGTON. D.C. 2055H001 February 4, 1998 MEMORANDUM FOR:
Ledyard B. Marsh, Chief Plant Systems Branch Office of Nuclear Reactor Regulation FROM:
Steven West, Chief Fire Protection Engineeri ection Office of Nuclear Reactor Regulation
SUBJECT:
PHONE CONVERSATION WITH REPRESENTATIVES OF DOW CORNING REGARDING FIRE BARRIER PENETRATION SEALS On September 19,1997, the NRC staff met with representatives of the Union for Concemed Scientists (UCS) and the Nuclear Information and Resource Service (NIRS) to discuss the of silicone-based materials in fire barrier penetration seals. The staff agreed to follow-up on two issuen that UCS and NIRS raised during the meeting. Both issues were based on a 1994 transcript of an NRC Office of Investigations (01) interview with Mr. Hitoshi Takahashi of Dow Coming, incorporated. On January 23,1998, Chris Bajwa and I discussed the issues with Lynn Krauss and Hitoshi Takahashi of Dow Coming Corporation.
Perry Silicone Foam Pine Pluo The first issue involved a 1986 event at the Perry nuclear p! ant where a hydrogen ignition i
occurred due to the accumulation of hydrogen gas from an installed silicone foam seal. The staff could find no record of the ev3nt in tir NRC archives. Because the event happened during pant construction, the licensee did not report it. Mr. Takahashi investigated the event, and was able to discuss it with the staff. According to Mr. Takahaahl, the seal was installed in a unique configuration which he had never witnessed before. The silk one foam was used to seal one end of a large pipe (6 feet in diameter) going ' ' rough the reactor containment wall.
Specific. ally, one side of the pipe was welded t nut w?h a steel plate, while the other side was sealed with the foar., on the irWde of containment. Mr. Takahashi stated that he thought that the silicone foam plug was.,istalled to prevent people from entering the pipe. A sketch of the configuration, which Mr. Takahashi faxed to us during our conversation wt1 him, is attached.
The silicone foam used to seal the pipe was poured a!! at once. Silicone oam has two components which ato mixed in a 1:1 ratio. The chemical reaction that occurs when the components are mixed releases hydrogen which causes the foam to ' snap" or expand in volume. In this case, the hydrogen that was released from the back side of the seal
. cumulated in the dead space between the foam seal and steel end plate which was used to close the pipe on the outside of the containment wall.
A day and a half after the silicone foam plug was installed, either cutting and welding or grinding was done on or near the plugged pipe. Upon investigation, it was believed that the cutting and
Contact:
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welding or grinding operation created an ignition source that ignited the hydrogen gas that had accumulated in the dead space between ths, seal and the steel end plate. -The force of the ignition broke apart the silicone foam seal. Pieces of the foam struck a worker who fell from a 15-foot scaffold. He was injured, but not seriously. According to Mr.- Takahashi, there was no r
damage to any equipment and no harm to additional personnel.-
Mr. Takahashi informed us that he prepared some notes at the time of his investigation, but
- given the time since the event, he did not know what had become of them. His recollection was 1
that he calculated that the hydrogen concentration wi'hin the enclosed pipe was about 4 percent. He stated that sihcone foam is pervious to hyologen and had the ignition not occurred, the accumulated hydrogen would have dissipated within about five days. Mr. Takahashi could j
. not recall anythin0 of this nature happening previous to or following the Perry event. The staff also has no record of any such events, outside of the'exampin at Perry, Mr. Takahashi noted that Dow Coming data sheets and product brochures for silicone foam products discuss the prwuction of hydrogen gas and installation precautions. In the Dow Coming pubhostion "Information About Dow Coming 3-6548 Silicone Foam," the section titled
' Safe Handling Information' states, in part; immediately upon mixing the A and B components of Dow Coming 3-6548 silicone RTV foam, a chemical reaction takes place that results in the (,eneration of hydrogen gas.
l Appropriate caution should be exercised Keep away from sparks arH open flame.
When using Dow Coming 3-6548 siliwne RTV foam to seal large penetration openings, i
care should be exercised to avoid gas entrapment. Adequate ventilation should be i.
provided to prevent build up of hydrogen gas... Adequate ventilation must be provided.
to ixeveat build up of hydrogen at explosive levels.
We have reviewed these materials and conclude that the information provided by Dow Coming is sufficsont to ensure that hydrogen is not a credible hazard during foam penetration seal
=insta :ation.
Fire Testina
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The second issue from the UCS/NIRS meeting concemed a statement that Mr. Takahashi made during the 01 interview regarding qualification tests of fire barrier penetration seals. He stated that 100 fire tests could be conducted on a particular configuration and if just one test
' was successful, then the seal configuration would tm qualified. During this teleconference he clarified that remark. Mr. Takahashi stated the h!a statement was an exaggeratlor:, and that it b
is not the practice in industry.- He stated that sincdy speaking, the fire test standards do not prevent a seal vendor from retesting a configuration until it passes, no matter how many tests -
r they run. (Note, this is true for all fire resistive construction and is not limited to fire barrier penetration seals.)- He stated that a configuration could be tested five or six times before it t
passed a fire test. His opinions were that there are variables (e.g., ambient temperature, humidity, furnace control, etc.)in a fire endurance test and not all of them can be controlled to ensure that the results of multiple fire endurance tests would be exactly alike. Mr. Takahashi i
also stated that it has been his experience that when multiple tests are performed, modifications
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L.B. Marsh 3-are made to the penetration sealinstallation between fire tests. Therefore, there are some differences from test to test. He also agreed that the margin in a particular seal design would compensate for ;he variables present dur;ng testing.
Mr. Takahashi stated that he has been involved in penetration seal test programs conducted at Undeiwriters Laooratories, Southwest Research Institute, Portland Cement Association, and a number of other labJratories that he coulei not recall. He stated that he knew of no forgery of test results for fire barrier penetration seals, and that in his observations of fire tests, he had not seen anything that would lead him to doubt the test results that were obtained. Finally, he stated that he was not aware of any penetration seals installed in nuclear power plants with questionable fire endurance test qualifications, in our opinion, the information provided by Mr. Takahashi provided an adequate basis for closing these two issues. Therefore, we do not plan to pursue these issues further. We will provide this information to UCS and NIP.S.
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