ML20057F922
| ML20057F922 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 10/13/1993 |
| From: | Fenech R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9310190348 | |
| Download: ML20057F922 (5) | |
Text
.. _ _ _ _. __ _
4 b
1 i
Tec,nwe Vd w A# r q F
,rO!' a 0 3 ? LO r d h fh
,4,.,
we 37379.~o7) l i
ftt,ert A. Fenech i
v i u <re ', y a r, t u m V.am October 13, 1993 U.S. Nuclear Regulatory Commission ATTN:
Document Control Desk Washington, D.C.
20555 I
Centlemen:
In the Matter of
)
Docket Nos. 50-327 Tennessee Valley Authority
)
50-328 SEQUOYAH NUCLEAR PLANT (SQN) - NRC INSPECTION REPORT NOS. 50-327, 328/93 REVISED REPLY TO NOTICE OF VIOLATION (NOV) 50-327, 328/93-05-03 Enclosed is TVA's revised response to Paul E. Fredrickson's letter to Mark O. Medford dated March 22, 1993, which transmitted the subject NOV.
The violation is associated with excessive leakage from the Unit I upper containment personnel airlock outer housing. The cause of the leakage improper installation of a blind flange on the outer housing of the was airlock.
L This response is being revised to provide additional information and
~
revised corrective actions associated with the subject NOV.
Those areas revised are noted by revision bars.
e The condition associated with this violation was previously reported in accordance with 10 CFR 50.73 by Licensee Event Report 50-327/93004, Revision 1, dated June 15, 1993.
There are no new commitments associated with this response.
l t
4 l
1900"2 OI
[ [g$f 9310190348 931013
??
DR ADOCK 05000327 l
]
e U.S. Nuclear Regulatory Cournission Page 2 October 13, 1993 If' you have any questions concerning this submittal, please telephone R. II. St.211 at (615) 843-8924.
i Sincerely,
[.f f. 7..<.
A-Robert A. Fenech Enclosure cc (Enclosure):
Mr. D. E. LaBarge, Project Manager
'U.S.
Nuclear Regulatory Conunission i
One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739 j
NRC Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road 4
Soddy-Daisy, Tennessee 37379-3624 Regional Administrator U.S. Nuclear Regulatory Commission Region JI 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323-2711 l
i t
t
}
i
ENCLOSURE RESPONSE TO NRC INSPECTION REPORT j
NOS. 50 127/93-05 AND 50-328/93-05 PAUL E. FREDRICKSON'S LETTER TO MARK 0. MEDFORD DATED MARCH 22, 1993 Viola d on__50232L_32883-01-03 "A.
Technical Specification 3.6.1.1 requires, in part, that primary containment integrity be maintained in MODES 1, 2, 3, and 4.
Technical Specification 3.6.1.2.c requires, in part, that containment leakage rates shall be limited to a combined bypass leakage rate of less than or equal to 0.25 La (56.3 scfh) for all penetrations identified in Table 3.6-1 as secondary containment bypass leakage paths to the auxiliary building when pressurized to P (12 psig). This requirement is applicable in MODES 1, 2, 3, a
and 4 (prior to increasing reactor coolant syster temperature above 200 degrees F).
Additionally, Technical Specification 3.6.1.3.b requires, in part, that each containment air lock shall be operable with an overall air lock leakage rate of less than or equal to 0.05 L (11.25 scfh) at a
P (12 psig) in MODES 1, 2, 3, and 4.
u Cnntrary to the above, on February 22, 1953 the licensee identified that a leak existed on a blind flange (approximately 52.6 scfh) located on the Unit I upper containment outer airlock bulkhead.
This leak resulted in a loss of primary containment integrity during the periods of time when the inner containment airlock door was opened.
The inner air lock door was determined to have been opened eight times for personnel access to/from containment coincident with the leakage at the blind flange from February 16, 1993 through the identification of the problem on February 22, 1993.
Due to the as-found total containment bypass leakage being f
approximately 59.7 scf h, the required containment bypass leakage limit of 56.3 scfh was exceeded during the periods of time when the inner containment airlock door was opened. The inner air lock door was determined to have been opened eight times for personnel access to/from containment coincident with the leakage at the blank flange f rom February 16, 1993 through the identification of the problem on February 22, 1993.
Due to the as-found airlock leakage of approximately 55.6 scfh, the allowable airlock leakage rate was exceeded resulting in inoperability of the airlock for the period of February 16 through February 22, 1993.
"This is a Severity Level IV problem (Supplement 1)."
~.
~
t f
f
- l lhcasonlor_thellolatiDn The cause of this condition was the improper installation of the subject blind flange. The outer 0-ring apparently slipped out of the machined groove and overlapped a portion of the inner 0-ring during the l
installation process. This overlapping of 0-rings created an artificial j
seal that prevented leakage detection during the normal postmaintenance
{
testing process.
The performance of a new test that pressurized the blind flange from the back side was required to quantify the leakage. A contributing cause to this condition was that the industry-accepted methodology of testing blind flanges failed to detect the mispositioned 0-ring since this testing does not pressurize both sides of the flange.
The industry-accepted method of testing this type of flange is to pressurize from the front side to ensure that there is no leakage between the 0-rings.
Co rre c t ive_ S t e rLIhatle vtDeca lakettan d_t he_Re smLt s_Achi eved t
l Corrective actions were immediately taken upon discovery of the condition in order to quantify the leakage and correct the adverse condition.
These actions included testing the blind flange to determine the amount of leakage, correcting the deficiency, and retesting the flange before declaring the airlock operable.
The individuals involved in this event have been counseled with regard to l
attention to detail in component installation.
Co r r e nlivtS t e r alh a t li1 Lb ela ken _lo_Avsi dlurt h e rliol a t. ion s An evaluation of the other 14 double 0-ring blind flanges per unit was performed to determine if a different test method was warranted (i.e.,
I testing from the backside).
It was found to be impractical on six flanges (size, configuration, radiation, accessibility).
The remaining flanges can be visually inspected from the backside and alternately tested if deemed necessary.
The practice of routine testing from the backside was reviewed by an independent consultant as part of an overall Appendix J program assessment and found to be very conservative with respect to Appendix J and containment integrity issues. The corrective action addressing the improper installation of the blind flange adequately addressed the
]
one-time nature of the event and additional test methods are unnecessary. Testing from the backside, utilizing a test plug, is also prone to failure as a result of plug leakage and may unnecessarily contribute to the measured containment leakage rate.
The practice of i
testing between the 0-rings is an industry-acceptable method that tests q
both 0-rings.
The test from the backside only establishes the integrity of a single 0-ring.
2 I
I i
l 1
d o
. Blind flanges with similar applications have been evaluated to determine whether alternate testing methods are appropriate.
Dat u.Wimn _ful LComplian ce_will_be_ Achieved TVA is in full compliance.
t 4
I 1
?
4 i
e i
-