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LER 95-002-00:on 950307,degraded Sealing Capability of Inner Door of Personnel Air Lock Discovered.Caused by Personnel Error.Need to Establish Teamwork & Anticipate Plan for Contingencies Discussed
	ML18064A685
Person / Time
Site:	Palisades
Issue date:	04/06/1995
From:	Gire P; CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	;
Shared Package
ML18064A684	List: ML18064A683; ML18064A685;
References
	LER-95-002-01, LER-95-2-1, NUDOCS 9504120175
	Download: ML18064A685 (6)
	v • d • e

NRC Form 388 18-831 FACILITY NAME 111 LICENSEE EVENT REPORT (LERI

U.S. NUCLEAR REGULATORY COMMISSION APPROVEO OMB NO. 3160-0104 EXPIRES: 8/31 /86 DOCKET NUMBER 121 PAGE 131 Palisades Plant 0 5 0 0 0 2 5 5 OF 6 TmE 141 Degraded Sealing Capability of Inner Door of Personnel Air Lock EVENT DATE 161 REPORT DATE 181 OTHER FACILITIES INVOLVED 181 REVISION FACILITY NAMES MONTH DAY YEAR YEAR NUMBER MONTH DAY YEAR N/A 0 6 0 0 0 0 3 0 7 9 5 9 5 0 0 2 0 4 0 6 9 5 N/A 0 6 0 0 0 THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 Cffl I: (Ch<<Jt .,,,. or,,,,,,. of tn. foMowin(IJ 1111 OPERATING MODEllll N 20.4021bl 20.406Ccl 60.731oll211ivl 73.711bl 20.4061oll1161 60.38Ccll11 60.731oll21M 73.71(cl 20.406Wl1 lliil 60.38(cll21 60. 7 3(oll2Hviil OTHER (Specify in - K l 20.4061oll1 Hiiil X 60.73Coll21PI 60.73(oll21CviiillAI bolow - in Text, 20.4061ol111fivl 60.73(ol(21Ciil 60.73(oll2Hviiill81 NRC Form 388AI 20.406CoJC1 IM 60.731oll21Ciiil 60.731oll21bd LICENSEE CONTACT FOR THIS LER 1121 NAME TELEPHONE NUMBER AREA CODE 1

Paul J Gire 6 6 7 6 4 - 8 MANUFAC* REPORTABLE MANUFAC* REPORTABLE CAUSE SYSTEM COMPONENT TUR ER TO NPRDS CAUSE SYSTEM' COMPONENT TUR ER TO NPRDS SUPPLEMENTAL REPORT EXPECTEO (141 MONTH DAY YEAR EXPECTED SUBMISSION YES llf'YH. ,_,,,.,.EXPECTED SUBMISSION Q<ITEJ DATE 1161 ABSTRACT Uimlt to 1400 _ ... l.o., -imar./y fiftwn ain(Jlo--* typewritten lino#I 1161 On March 7, 1995, while the plant was operating at 100% power, a pressure test was in progress on the personnel air lock door seals. The inner door seals were being tested and the required test pressure of 15 psig quickly dropped during the initial stabilization period of the test.

The operator performing the test was instructed by the Control Room Supervisor to enter the personnel air lock to gain access to the inner door and verify it was closed tightly. Based on the calculated results of the inner door seals leak rate, the temporary opening of the outer door for this two minute entry into the air lock violated containment integrity requirements.

The cause of this event was an error in judgement by the Control Room Supervisor that resulted from ineffective teamwork and not maintaining a questioning attitude which led to the inappropriate action taken.

Corrective actions include: Discussions with Operations shift personnel on the need to establish teamwork and to anticipate and plan for contingencies; and an evaluation of the post-test airlock door seal maintenance activities to determine why the personnel air lock inner door seals did not successfully pass the pressure leak test.

9504120175 950406 PDR ADOCK 05000255 S PDR

NRC Form 388A U.S. NUCLEAR REGULATORY COMMISSION (11-831 APPROVED OMB NO. 3160-0104 EXPIRES: 8/31186 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION FACILITY NAME 111 DOCKET NUMBER 121 LER NUMBER (31 PAGE 141 SEQUENTIAL REVISION YEAR NUMBER NUMBER Palisades Plant 0600026696-002 Q 2 OF Q .6 Event Description On March 7, 1995, while the plant was operating at 100% power, a pressure test was in progress on the personnel air lock [NH;ALJ door seals. The Technical Specification Surveillance Procedure (TSSP) DW0-13, "LLRT - Local Leak Rate Test for Inner and Outer Personnel Air Lock Door Seals ", was required to be completed within 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months after the air lock doors were opened.

DW0-13 is the between-the-seals test for the Personnel Air Lock Doors. The doors had been opened to remove test equipment and restore air lock components to pre-test conditions after the completion of the semi-annual full pressure air lock test, S0-4A, " Personnel Airlock Penetration Leak Test."

The personnel air lock inner door seals were being tested* first and the required test pressure of 15 psig quickly dropped during the initial stabilization period of the test. The Auxiliary Operator (AO) performing the test contacted the Control Room Supervisor (CRS) regarding the unexpected pressure drop for the inner door seals. The CRS instructed the AO to enter the personnel air loc to gain-access to the inner door and verify it was closed tightly. _The other two licensed senior reactor operators on the shift were not consulted prior to this decision. The AO entered the personnel air lock through the outer door and leaving the outer door in the open position verified the inner door was closed tightly. The inner door was found in the fully closed position and the AO exited the air lock and closed the outer door. The outer door was open for approxi_m~tely two minutes. Based on the calculated results of the inner door seals leak rate, the temporary opening of the outer door for this two minute entry' into the air lock violated containment integrity requirements. Containment Integrity must be maintained unless the reactor is in a cold shutdown condition.. Containment integrity also requires that at least one door in the personnel air lock is properly closed and sealed. For the two minute period, the outer door was open and the inner door was not properly sealed per the testing acceptance criteria.

During the evaluation of this event it has also been determined that during previous restoration activities from the air lock full pressure test, the outer door had been open for short time periods with the inner door seals degraded. Palisades Technical Specifications do not presently contain allowances for temporary entries into air locks through an operable. air lock door to gain access to an inoperable air lock door for repairs.

The Shift Supervisor (SS) was performing a plant walkdown when he was notified of the air lock testing problem. When the SS arrived at the personnel air lock after the AO had reclosed the outer door, it was realized that containment integrity may have been violated. The SS confirmed the temporary loss of containment integrity when he had the AO perform another DW0-13 local leak rate test to quantify the leak rates for the inner and outer doors. The outer door between-the-seals leak rate was acceptable at 468 cc/min, however the inner door leak rate was estimated at 89,840 cc/min. The SS had the personnel air lock card reader de-energized to restrict any further entries, and the outer door was wired closed.

NRC Form 3811A U.S. NUCLEAR REGULATORY COMMISSION '

(9-1131 APPROVED OMB NO. 31~104 EXPIRES: 8/31 /86 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION FACILITY NAME 111 DOCKET NUMBER 121 LER NUMBER (31 PAGE 141 SEQUENTIAL REVISION YEAR NUMBER NUMBER Palisades Plant 0500025595-002 0 3 OF 0 6 Palisades Technical Specification 4.5.2.b.(2) requires the air lock between.-the-seals leak rates to be maintained below 2.3% of the containment design leakage, (0.023 L.) which equates to 2500 cc/min. If air lock door leakage is greater than 0.023 La then repairs shall be initiated immediately to restore the air lock leakage to less than 0.023 L. within a 7 day period.

Additionally, Palisades Technical Specification 4.5.2.b.(1) requires the total leakage from all penetrations and isolation valves be maintained below 0.60 L*. which equates to 65,200 cc/min.

The total containment leakage at this particular time was the summation of the inner door leakage rate of 89,840 cc/min plus the total measured leakage for all other containment penetrations, 11,428 cc/min, which leads to a total of 101,268 cc/min or 0.93 L*. According to Technical Specifications, if air lock door seal leakage results in one door causing total containment leakage to exc~ed 0.60 L., the door shall be declared inoperable and the remaining operable door shall be immediately locked closed and tested within four hours. A 48 hour5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months action statement is applicable in this case to restore the inoperable door leakage to below 0.60 L*.

The inner air lock door was declared inoperable at 0515 hours0.00596 days 0.143 hours 8.515212e-4 weeks 1.959575e-4 months and the event was recognized as being immediately reportable due to the principal safety barrier (containment) being degraded. A one-hour nonemergency notification was made per 10 CFR 50. 72. (b)( 1 )(ii). The personnel air lock inner door was accessed for repairs by entry through the alternate containment emergency escape air lock. Minor adjustments were made to the inner door seals and an adjustment was made to a door latching bracket to ensure the brackets closing forces were evenly distributed.

The cause for the excessive between-the-seals leakage was a failure to restore the inner door seals from the compression set that occurs during the full pressure air lock test.* The inner door was declared operable at 1515 hours0.0175 days 0.421 hours 0.0025 weeks 5.764575e-4 months that same day based upon a successful between-the-seals leakage test result of 39.9 cc/min. * *

Analysis Of The Event Based on the evaluation of this event, it has been determined that, there were several short duration entries and exits through the outer air lock door that occurred during the time period tha the inner door seals were degraded. The inner and outer door seals have always experienced a compression set caused by the clamping and pressure forces that are exerted on the door seals during the performance of the full air lock pressure test. The compression set does not affect the safety performance of the air lock doors but it does complicate the restoration from full pressure tests. The maintenance procedures that follow the full *air lock pressure test require the restoration of one air lock door at a time to ensure containment integrity is maintained. The outer door is opened and the outer door seals are restored to their normal position. This restoration is only required to allow the door 'seals to pass the subsequent between-the-seals testing. A seal contact check is completed to provide verification that the outer door seals integrity has been restored and the outer door is closed. The door clamps are then removed from the inner door an

NRC Form 388A UHl31

LICENSEE EVENT REPORT (LERI TEXT CONTINUATION U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 3160-0.104 EXPIRES: 8/31 /86 FACILITY NAME 111 DOCKET NUMBER 121 LER NUMBER 131 PAGE 141 SEQUENTIAi. REVISION YEAR NUMBER NUMBER Palisades Plant ojsjolojoj2jsls e js - o jo j2 - I o 14 oF o Is it is opened to reposition its door seals to their original condition. The restoration of the sealing capability is also verified on the inner door by a similar seal contact check. The inner door is closed and at this time the repairmen exit through the outer door.

The opening of the personnel air lock outer door during the periods when exces~ive inner door leakage existed did not significantly degrade containment integrity for the following reasons:

1. The between-the seals test, DW0-13, applies a pressure of 15 p.sig between the two door seals. The leak rate is then calculated by using the pressure drop in the annulus between the two seals over a period of time. This testing cannot distinguish if the leakage is past just one seal or a combination of two seals. The actual maximum leak rate from containment past the two door seals in series would be 50% of the leak rate measured during the between-the-seals test. From this perspective, the measured between-the-seals leakage rate of 89,840 cc/min would equate to a maximum containment leakage rate past both seals of 44,920 cc/min which is 0.41 L*.

2. Additionally, containment pressure during an actual accident would a*ssist the sealing force on the personnel air lock door and would significantly enhance the sealing capability of the inner door seals. The between_.the-seals test pressure is applied in a direction opposite the postulated containment accident pressure and tends to unseat the door. The fail safe design capability of the air lock doors is demonstrated by the leak rate measured during the full air lock pressure test just prior to the door seals testing. Door clamps are installed on the inner door to simulate the closing force of the containment internal pressure. The leak

. rate for the entire air lock at 55 psig was measured at 26 cc/min. This significantly lower leak rate is more indicative of the design basis performance of an inner door with two seals in series and design differential pressure against the door.

3. The personnel air lock outer door was opened for only a short duration, about two minutes, and was under the direct control of an AO. The actions of the Operations personnel were .

consistent with the allowed actions in Standard Technical Specifications (NUREG 1432) which allow temporary entries and exits through the one operable door of an air lock to provide access to the inoperable door for repairs.

The post-test adjustments to the door seals anq contact checks are performed solely to restore the air lock door functionality for satisfactory completion of the between-the-seals test. It is very likely that the door seals will always function to significantly limit containment leakage during an event when a pressure differential forces the doors closed. It is evident from this particular event

NRC Form 388A 19-831

LICENSEE EVENT REPORT (LERI TEXT CONTINUATION U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 31So-0104 EXPIRES: 8/31 /86 FACILITY NAME Cl I DOCKET NUMBER 121 lER NUMBER 131 PAGE 141 SEQUENTIAL REVISION YEAR NUMBER NUMBER Palisades Plant I oI 5 oF o Is that the seal contact check does not necessarily ensure that the restored seals will always pass the between-the-seals test. The between-the-seals test is a more conservative test, with respect to verification of door operability than the full pressure air lock test. Therefore, the doors can perform their design function yet not pass the between-the-seals test. At this time there appears to be no alternate testing method available that would more appropriately test the door seals and not contain excessive conservatism like the between-the-seals test method.

Cause Of The Event The cause of this event was an error in judgement when the CRS instructed the AO to open the outer air lock door to verify the inner door was closed tightly. The error in judgement by the CRS resulted from ineffective teamwork and a lapse in maintaining a questioning attitude which led to the inappropriate action taken. The CRS knew that the.previous full pressure air lock~*test had resulted in a minimum leak rate and the gasket contact checks were satisfactory. This led. the CRS to believe that the most likely cause of inner door leakage was due to the inner door not being tightly secured. Gasket integrity was not suspected to be the cause based on the previous satisfactory testing results. Though the leak rate was not initially quantified, the CRS did not recognize that the obtained DW0-13 leak rate could have contributed to the total containment leak rate such that the total leak rate could have exceeded 0.6 L11 . (65,200 cc/min). Therefore the CRS, thinking the personnel air lock inner door had exceeded 0.023 L11 but not considering that it may have exceeded 0.6 L11 , instructed the Auxiliary Operator to enter the personnel air lock to access the inner door and verify it \/\(as closed tightly.

Though a pre-job briefing was not required or conducted for this activity, pretest planning should have facilitated a pre-determined and thoughtful response to this event. The pre-planning effort should have addressed DW0-13, section 5.3.2 requirement that states "If pressure decays rapidly, omit stabilization and take readings at frequent intervals." Also, Technical Specifications, section 4.5.2, which describes actions required if leakage exceeds 2500 cc/min, should have been researched and understood prior to commencing the test. Teamwork was not utilized by the CRS in that other resources such as the Shift Supervisor and Shift Engineer were not notified or consulted. This negated any input these individuals may have had based on their experience and knowledge. The working copy of DW0-13 was with the AOs and was not referred to by the CRS. The CRS did not maintain a questioning attitude to gather the needed .

information to make the appropriate decision.

A contributor to this event was the maintenance restoration activities that failed to adequately prepare the inner door seal for the DW0-13 test. The failure of the personnel air lock inner door seals resulted from the "set" taken by the seals when the strongbacks were installed for S0-4A testing. This seal "set" condition is caused by the installation of the strongbacks. The

NRC Form 388A IS.-831 *

LICENSEE EVENT REPORT (LERI TEXT CONTINUATION U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 3160--0104 EXPIRES: 8/31/86 FACILITY NAME ll I DOCKET NUMBER 121 LER NUMBER 131 PAGE 141 SEQUENTIAL REVISION YEAR NUMBER NUMBER Palisades Plant I o Is oF o Is tightening of the strongbacks drives the seal bead approximately three-eights of an inch into the door seal groove. The seal remains in this compressed condition for the entire period the test is being performed (approximately five hours). When the strongbacks are removed the seals do not quickly and fully rebound to their pretest condition. This condition was documented to the NRC in letters dated September 21, 1987 and November 15, 1990. It is also discussed in the Technical Specification Surveillance Procedure S0-4 Basis Document. In 1985 seal material changes were investigated and no improvements were determined to be. available. In 1986 Palisades began performing seal contact checks and seal adjustments subsequent to air lock testing (strongback removal) in attempt to restore the seals to their pretest condition.

A second contributor to this event is the rigid existing Palisades Technical Specification requirements that allow no flexibility to access an inoperable air lock door through the operable door. Standard Technical Specifications (NUREG 1432) allow periodic short entries through operable air lock doors to complete repairs to an inoperable airlock door. The short duration of the entries, and the design capabilities of airlock doors were recognized during the development

of Standard Technical Specifications (NUREG 1432), and thus they allow the* entries under administrative controls for a one week period.

Corrective Actions The following corrective actions have been taken:

1. Palisades Work Order No. 24510545 performed troubleshooting and adjusted the latching brackets of the personnel air lock inner door. Subsequent DW0-13 testing resulted in acceptable leak rates.

2. The Shift Operations Superintendent issued Daily Orders, on March 8, 1995, and discussed with each shift the need to establish teamwork and provide advance anticipation and planning for contingencies. No further actions required.

The following corrective actions will be taken:

1. Evaluate the airlock door seal preparation activities of Maintenance Procedure CLP-M-4.

2. Continue with the planned actions and commitments to institute Standard Technical Specifications for the Palisades Plant. Our plans and commitments in this area have been communicated to the NRC in separate correspondence.

ML18064A685

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