ML20035F941
| ML20035F941 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 04/20/1993 |
| From: | Fenech R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9304230103 | |
| Download: ML20035F941 (4) | |
Text
.
4 9
1 Tennessee Vafley Authanty, Post Offee Box 20m Sxtdy-Daisy, Tennessee 37379 20">0 -
Robert A. Fenech Vice President Soaucyah Nuclear Plant April 20, 1993 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Gentlemen:
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 REPLY TO NOTICE OF VIOLATION (NOV) 50-327, 328/93-05-03 Enclosed is TVA's 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 1 upper containment personnel airlock outer housing. The cause of the leakage was improper installation of a blind flange on the outer housing of the airlock.
The condition associated with this violation was previously reported in accordance with 10 CFR 50.73 by Licensee Event Report 50-327/93004 dated March 23, 1993. There are no new commitments associated with this response.
{
If you have any questions concerning this submittal, please telephone M. A. Cooper at (615) 843-8924.
Sincerely, i
j$h4A Robert A. Fenech Enclosure cc: See page 2 230058 1'
9304230103 930420 l
PDR ADOCK 05000327 I
I G
PDR D
i
i s
\\
r U.S. Nuclear Regulatory Commission Page 2 i
April 20, 1993 l
l cc (Enclosure):
L Mr. D. E. LaBarge, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739 I
NRC Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road i
Soddy-Daisy, Tennessee 37379-3624 I
Regional Administrator U.S. Nuclear Regulatory Commission l
Region II 101 Marietta Street, NW, Suite 2900 l
Atlanta, Georgia 30323-2711 1
l l
1
)
l i'
t ENCLOSURE j
RESPONSE TO NRC INSPECTION REPORT
{
NOS. 50-327/93-05 AND 50-328/93-05 PAUL E. FREDRICKSON'S LETTER TO MARK 0. MEDFORD DATED MARCH 22, 1993 I
Violation 50-327. 328/93-05-03 l
i "A.
Technical Specification 3.6.1.1 requires, in part, that primary containment integrity be maintained in MODES 1, 2, 3, and 4.
i 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 L, (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 Pa (12 psig). This requirement is. applicable in MODES 1, 2, 3, j
and 4 (prior to increasing reactor coolant system temperature above 200 degrees F).
i Additionally, Technical Specification 3.6.1.3.b requires, in part, t
that each containment air lock shall be operable with an overall air i
lock leakage rate of less than or equal to 0.05 L, (11.25 scfh) at P, (12 psig) in MODES 1,2,3, and 4.
Contrary to the above, on February 22, 1993 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 j
the periods of time when the inner containment airlock door was opened. The inner air lock door was determined to have been opened i
eight times for personnel access-to/from containment coincident with i
the leakage at the blind flange from February 16, 1993 through the identification of the problem on February 22, 1993.
1 l
Due to the as-found total containment bypass leakage being l
approximately 59.7 scfh, 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 l
to/from containment coincident with the leakage at the blank flange l
from 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)."
l-1 i
I
. _. ~,
c
~,,, -.,,.
e t
_2-Reason for th;_ Violation 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 installation process. This overlapping of 0-rings created an artificial 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 quentify the leakage. A contributing cause to this condition was that the industry-accepted methodology of testing blind flanges failed to detect the mispositioned I
0-ring since this testing does not pressurize both sides of the flange.
The industry-accepted methsd of testing this type of flange is to pressurize from the front side to ensure that there is no leakage between the 0-rings. However, by also pressurizing from the back side of the flange, testing would assure detection of an artificial seal.
Corrective Steps That Have Been Taken_and_the_Reaults Achieved 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 attention to detail in component installation.
Corrective S_teps_Ihat Will be Taken to Av_nid_Eurther Violations The surveillance instruction that tests the containment personnel airlocks will be revised to include testing of the back side of the subject blind flange.
Blind flanges with similar applications will be evaluated to determine whether alternate testing methods are appropriate.
Date_When Full _ Compliance will be Achiev_ed TVA is in full compliance.
-