ML18054A822
| ML18054A822 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 06/30/1989 |
| From: | Berry K CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 8907050211 | |
| Download: ML18054A822 (3) | |
Text
consumfdl~s Power POWERINli MICHlliAN"S PROliRESS General Offices: 1945 West Parnell Road, Jackson, Ml 49201 * (517) 788-1636 June 30, 1989 Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 Kenneth W Berry Director Nuclear Licensing DOCKET 50-255 - LICENSE DPR PALISADES PLANT -
CONSUMERS POWER COMPANY POSITION REGARDING EQUIVALENCY OF SEAL CONTACT CHECK TO A BETWEEN THE SEALS TEST -
INSPECTION REPORT 89009 NRC Inspection Report 50-255/89-009 dated April 21, 1989 transmitted one notice of violation for failing to perform a between the seal test of the escape airlock door within three days after door usage in accordance with 10CFR Part 50, Appendix J, III.D.2.(b)(iii).
Consumers Power's written response provided on May 22, 1989 acknowledged that this type of testing had not been completed on the escape lock due to its physical design configuration and committed to provide written documentation which delineates the equivalency of the seal contact check to a reduced pressure between the seals test.
10CFR Part 50, Appendix J requires testing of airlocks to assure continued integrity of the sealing surf ace within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> of any opening of their doors and testing at containment design pressure at intervals not to exceed six months.
This testing may be accomplished by the full Type "B" airlock test or by testing the seals for airlock doors designed to accommodate this testing.
This test shall be performed at containment design pressure unless specified differently with the Plant Technical Specification (TS).
This testing, for the escape airlock, is accomplished by TS Surveillance Test S0-4B, "Escape Airlock Penetration".
To perform the test, strongbacks are installed within the airlock for the inner door.
This test is an eight hour test with a one hour stabilization period prior to taking data.
Palisades' escape lock is configured to allow testing between the seals, however, the door locking pins do not provide uniform closure force thus the strongbacks must be installed for all testing.
The escape lock vendor has reviewed the design and determined the compression seal airlock at Palisades would not be leak-tight for between the seal testing without use of strong-backs at reduced pressures.
The airlock was not originally designed for testing between the seals without tes.t clamps in place.
To verify statements presented by the airlock vendor and Consumers Power engineering personnel's 8907050211 890630 PDR ADOCK 05000255 Q
PDC OC0689-0012-NL02
Nuclear Regulatory Commission
- Palisades Nuclear Plant Equivalency of Seal Contact Check June 30, 1989 analysis of the escape lock's ability to mee.t a between the seals test, S0-4B was temporarily revised to perform a reduced pressure test between the seals without strongback installation.
On May 10, 1989 this test was performed on the escape lock which had fluffed seals and a seal contact check.
During testing, the inner and outer door seals began leaking at 10 psig and 11 psig respectively when initially pressurized.
- Both doors decayed in pressure, approximately one second after pressurizing to 15 psig, with the outer door dropping to one psig and the inner door dropping to six psig.
Since these results verified that the escape airlock design would not accommodate partial pressure between the seals testing without strongbacks, a partial S0-4B was satisfactorily performed to verify escape lock integrity in accordance with Plant TS.
Past TS surveillance testing has shown that testing with strongbacks in place at containment design pressure causes the seals to take a set. After strong-back removal, the door must be opened and the seals "fluffed" to obtain the sealing surface which was present prior to testing.
The seal "fluffing" is required because the force of the strongbacks on the inner door and the force due to the test pressure on the outer door draws the seal bead on the doors further into the seal than obtained with normal door closure.
That is, the applied pressure actually forces the metal sealing surf ace of the door onto 2
the outer edge of the metal seal groove of the airlock bulkhead.
With strong-backs installed and test pressures applied, the seal bead will be approximately three-eights of an inch into the seal.
The seal will remain in this compressed condition for the 12 to 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period that the test is being performed, causing the seal to take a set in the seal groove of the airlock bulkhead.
The bulkhead that the seal sits in has an as-cast finish.
Therefore, irregularities existing within the seating surface result in the seal face having peaks and valleys.
Past test performances have shown that once the strongbacks are removed, the seals have taken a set and will not rebound to the pretest position.
At this time during the performance of the TS surveil-lance test, a seal contact check is performed.
The seal contact check consists of applying a layer of grease on the seal face and then closing and reopening the airlock door.
The prope~ties of the grease will demonstrate a pattern respective of the door seal bead.
Acceptance criteria for the contact check are contained in Maintenance Procedure CLP-M-4, "Airlock Strongback Installation and Personnel Lock Equalizing Valve Leak Check/Adjustment".
This procedure states that, "an acceptable bead pattern will run continuously 9-round the length of the seals and be one-eighth to one-quarter inch wide".
If this criterion is not met the seals are fluffed in the area of the gap allowing the seals to rebound to their pretest position.
Following fluffing, a second seal contact check is performed to verify the integrity of the sealing surface.
Palisades has proven the success of the seal fluffing program on the personnel airlock where this technique is also utilized.
The personnel airlock design does allow a reduced pressure between the seals test without strongbacks.
This test is conducted via TS Surveillance Test DW0-13, "LLRT, Local Leak Rate Test For Inner and Outer Personnel Airlock Door Seals" in accordance with OC0689-0012-NL02
, * ~tfclear Regulatory Commission
- Palisades Nuclear Plant Equivalency of Seal Contact Check June 30, 1989 10CFR Part 50, Appendix J, III.D.2.(b)(iii).
Following seal fluffing, DW0-13 results are typically less than 70 cubic centimeters per minute, compared to the acceptance criterion of 2500 cubic centimeters per minute.
Prior to utilization of the seal fluffing technique in 1986, the personnel airlock doors experienced three failures of the between the seals test following a full pressure test and had an average leak rate on successful tests of 255 cubic centimeters per minutes.
Since the inception of seal fluffing in 1986, the personnel airlock has only failed DW0-13 twice following a full pressure test.
On one of these occasions, the repairmen failed to fluff the seals as required by CLP-M-4 and on the other a paint chip was found on the seal face causing the failure.
Therefore, neither of these failures were attributed to the seal fluffing or contact check program.
3 Between the seals test on the personnel airlock continually pass the subsequent tests following the seal fluffing after full airlock test.
The problem with the low spots does not occur with normal door openings and closings so the seal fluffing is not performed.
The cause of the seal taking a set is con-sidered to be due to maintaining the seals in a compressed state for extended periods of time.
The seal fluffing is considered permanent restoration of the seals, controlled by approved Plant procedures.
Based on the success of the seal fluffing and seal contact check on the personnel airlock as shown by the previously mentioned, between the seals test, Consumers Power Company believes that the analogy can be drawn that integrity of the escape airlock door seals can be shown by successful perform-ance of the seal contact check, even though a between the seals test cannot be performed because of the escape airlock design.
Therefore, Consumers Power plans to continue usage of the present methods of testing the escape airlock.
This includes a full pressure complete airlock test every six months, or after door openings, followed by strongback removal and restoration of door seals by fluffing and seal contact checks.
Acceptance of this position by the NRC will result in Consumers Power Company submitting an exemption request to 10CFR50 Appendix J III.D.2(b).
Kenneth W Berry Director, Nuclear Licensing CC Administrator, Region III, USNRC NRC Resident Inspector - Palisades OC0689-0012-NL02