05000336/LER-1996-041-02, :on 961217,invalid Local Lrt of Fuel Transfer Tube Flange Discovered Due to Blockage of Test Port W/ Silicon Rubber Sealant Compound & Lack of Procedural Guidance.Developed Procedure

:on 961217,invalid Local Lrt of Fuel Transfer Tube Flange Discovered Due to Blockage of Test Port W/ Silicon Rubber Sealant Compound & Lack of Procedural Guidance.Developed Procedure

ML20133M246
Person / Time
Site:	Millstone
Issue date:	01/15/1997
From:	Laudenat R NORTHEAST NUCLEAR ENERGY CO.
To:
Shared Package
ML20133M237	List: 05000336/LER-1996-041, Forwards LER 96-041-00,documenting Event at Plant on 961217.Commitments Made Re Event Listed 05000336/LER-1996-041-02, :on 961217,invalid Local Lrt of Fuel Transfer Tube Flange Discovered Due to Blockage of Test Port W/ Silicon Rubber Sealant Compound & Lack of Procedural Guidance.Developed Procedure
References
LER-96-041-02, LER-96-41-2, NUDOCS 9701220314
Download: ML20133M246 (3)

LER-1996-041, on 961217,invalid Local Lrt of Fuel Transfer Tube Flange Discovered Due to Blockage of Test Port W/ Silicon Rubber Sealant Compound & Lack of Procedural Guidance.Developed Procedure

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(ii) 10 CFR 50.73(a)(2)(iv), System Actuation 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
3361996041R02 - NRC Website

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NRC FORM 366 U.s. NUCLEAR REGULATORY COMMisslON APPROVED BY OMB NO. 3150-0104 j

EXP1RES 04/30/98 LICENSEE EVENT REPORT (LER)

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MANAGEMENT ANo BUDGET WASHINGTON. DC 20503 FCEILITY NAME (1)

DOCKET NUMBER (2)

PAGE (3) q Millstone Nuclear Power Station Unit 2 05000336 1OF3

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TITLE 14) i invalid Local Leak Rate Test of Fuel Transfer Tube Flange due to Blockage of Test Port with Silicon Rubber i

Sealant Compound j

EVENT DATE (5)

LER NUMBER (6)

REPORT DATE (7)

OTHER FACILITIES INVOLVED (8)

SEQ AL RE MONTH DAY YEAR WAR MONTH DAY YEAR U E U

I 12 17 96 96

-- 041 --

00 01 15 97 l'

OPERATING THis REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR 5: (Check one or more) (11) 5 j

MODE (9) 20.2201(b) 20.2203(a)(2)(v)

X 50.73(a)(2)(i)

So.73(a)(2)(viii)

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POWER 20.2203(a)(1) 20.2203(a)(3)(i) 50.73(a)(2)(ii)

So.73(a)(2)(x)

I LEVEL (1o) 20.2203(a)(2)(i) 20.2203(a)(3)(ii) 50.73(aH2)(iii) 73.71 20.2203(a)(2)(ii) 20.2203(a)(4) 50.73(a)(2)(iv)

OTHER l

j 20.2203(a)(2)(iid So.36(c)(1)

So.73(a)(2)(v)

SpecygpA r t elow 20.2203(a)(2)(iv)

So.36(c)(2)

So.73(a)(2)(vii) i LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER tinclude Area Code)

R. T. Laudenat, MP2 Nuclear Licensing Manager (860) 444-5248 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

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CAUSE

SYSTEM COMPONENT MANUFACTURER

CAUSE

SYSTEM COMPONENT MANUFACTURER O NPRD O PRD i

1 SUPPLEMENTAL REPORT EXPECTED (14)

EXPECTED MONN DAY YEAR YEs Submission X NO DATE (15)

(If yes, complete EXPECTED sVBMisslON DATE).

ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16) 3 On December 17,1996 at 0400 during the removal of the blind flange from the fuel transfer tube, it was discovered

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j that the local leak rate test (LLRT) port for the blind flange seal was plugged. Thus, the LLRT performed following i

j the last assembly of the blind flange as required by Technical Specification Surveillance Requirement 4.6.1.1.d was not valid. The fuel transfer tube blind flange is a primary containment isolation device and is required to be leak tested by Technical Specification Surveillance Requirement 4.6.1.1.d after each closure. The blind flange was last installed on June 4,1995 by a work order during the last refueling outage. During this installation, a silicon rubber sealant compound was used to hold the blind flange O-rings in place during assembly. Excess sealant was squeezed into the test port located between the O-rings when the blind flange was torqued into place. This problem was not identified until the blind flange was subsequently removed on December 17,1996 to support the current outage.

The cause of this event was the lack of procedural guidance detailing an acceptable method for holding the O-ring in place during installation and detailing any Cautions in the use of sealants near the test pressurization port.

As a result of this event, a procedure will be developed to control the assembly / disassembly of the fuel transfer tube blind flange.

9701220314 970115 PDR ADOCK 05000336 S

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NRC FORM 366 (4-95) i

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'U.s. NUCLEAR REGULATORY COMMisslON (4?95)

UCENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1)

DOCKET LER NUMBER 16)

PAGE (3)

SEQUENTIAL REVislON YEAR NUMBER NUMBER 2OF3 Millstone Nuclear Power Station Unit 2 05000336 TEXT Uf more space is required, use additional copies of NRC Form 366A) t17)

I 1.

Descriotion of Event On December 17,1996 at 0400 during the removal of the blind flange from the fuel transfer tube [DF), it was discovered that the local leak rate test (LLRT) port for the blind flange seal was plugged. Thus, the LLRT performed following the last assembly of the blind flange as required by Technical Specification Surveillance Requirement 4.6.1.1.d was not valid. At the time of discovery of this event, the unit was in Mode 5 at 0 percent power.

The fuel transfer tube blind flange is a primary containment [NH] isolation device and is required to be leak tested by Technical Specification Surveillance Requirement 4.6.1.1.d after each closure. The blind flange was last installed on June 4,1995 by a work order during the last refueling outage. During this installation, a silicon rubber sealant compound was used to hold the blind flange O-rings (SEAL]in place during assembly. Excess sealant was squeezed into the test port located between the O-rings when the blind flange was torqued into i

place. This problem was not identified until the blind flange was subsequently removed on December 17,1996 I

to support the current outage.

The work order used to ' stall the blind flange during the last refueling outage did not specify the use of any material to hold the O-rings in place even though a glue material was used during mock up tests prior to initial installation in 1989 (see Analysis of Event below). Additionally, the work order did not provide a caution to ensure that the test port would remain clear during installation of the blind flange.

LLRTs were performed on the fuel transfer tube blind flange on June 5,1995 (post assembly) and on August 8, 1996 (prior to disassembly) with acceptable values of 55 standard cubic centimeters per minute (SCCM) and 20 SCCM, respectively. However, since the test port was plugged with the silicon rubber sealant compound, the LLRTs did not provide accurate leakage rates for the blind flange seals. Therefore, the testing requirements of Technical Specification Surveillance Requirement 4.6.1.1.d were not met during the last operating cycle.

This event is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B), any operation or condition prohibited by the plant's Technical Specifications.

II. Cause of Event

The cause of this event was the lack of procedural guidance detailing an acceptable method for holding the O-ring in place during installation and detailing any cautions in the use of sealants near the test pressurization port.

Ill. Analysis of Event The fuel transfer tube extends through the containment wall and allows for fuel movement between the refueling pool inside containment and the spent fuel pool in the auxiliary building. The containment penetration consists of the fuel transfer tube (36-inch diameter stainless steel tube) installed inside a 42-inch sleeve. The fuel transfer I

tube is fitted with a blind flange in the refueling pool and a standard gate valve in the spent fuel pool transfer canal to allow closure of the containment penetration when primary containment integrity is required. The blind i

flange connection includes two concentric O-rings which fit into machined grooves in the mating flange on the j

fuel transfer tube. A test connection is provided between the O-rings to allow leak testing of this containment

' boundary.

j The use of O-rings to replace the original flexible gaskets was established in 1989 as part of a plant modification.

This modification implemented several changes to make the removal and installation of the blind flange easier, j

and, thus, reduced the time spent in the high radiation area at the fuel transfer tube.

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..U.s. NUCLEAR REGULATORY COMMISSION (4 95)

UCENSEE EVENT REPORT (LER) i TEXT CONTINUAT!ON I

FACILITY NAME (1)

DOCKET LER NUMBER 16)

PAGE (3)

SEQUENTIAL Revision YEAR NUMBER NUMBER 3OF3 Millstone Nuclear Power Station Unit 2 05000336 i

96 - 041 -

00 TEXT fit more space is required, use additional copies of NRC Form 366A) (17)

Plugging of the test port with the sealant would have prevented the pressurization of the space between the O-rings and, therefore, testing of the leak tightness of the containment boundary. Although the leak tightness of the O-ring seal was not tested, it is not likely that the leakage rate through this penetration was unacceptable.

j The double O-ring design would require that both O-rings leak to create a pathway out of containment. After the removal of the blind flange, both O-rings were observed intact within their grooves with no damage noted. Also, i

although the sealant prevented the testing of the leak-tightness, the sealant would be expected to enhance the seal between the flange surfaces. Additionally, the integrated leakage rate test which exposes the blind flange and transfer tube extemals to containment design pressure was successfully performed several days after the a

l blind flange was installed and tested. Based on the above, this event is not considered to be safety significant.

IV. Corrective Action

As a result of this event, a procedure will be developed to control the assembly / disassembly of the fuel transfer tube blind flange. This procedure willinclude appropriate precautions to ensure that the LLRT test connection / port will not be blocked during the installation of the blind flange. This procedure will be completed prior to assembly of the fuel transfer tube blind flange during the current outage.

V.

Additional Information

No previous similar events were identified which involved the invalidation of LLRT results or the use of excessive sealants.

Energy industry identification System (Ells) codes are identified in the text as [XX].

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