ML20217G497
| ML20217G497 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 09/30/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20217G493 | List: |
| References | |
| NUDOCS 9710100232 | |
| Download: ML20217G497 (7) | |
Text
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NUCLEAR RE2ULATORY COMMISSIEN WASHINGTON, D.C. acte 6-00M
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.177TO FACILITY OPE lMTING LICENSE NO,_QPR-20 CONSUMERS ENERGY COMPANY PALISADES PLANT DOCKET NO. 50-255 1.0 LNTRODUCTION By letters dated January 10,1996, and February 20,1997, Consumers Power Company (now known as Consumers Energy Company) proposed a Technical Specification (TS) change ragarding Type B (local leakage rate) testing of the containment emergency escape airlock at l
the Palisades Plant. Specifically, the licensee proposed revisions to TS 4.5.2 to perform a l
seal contact check on the emergency escape airlock door seals in lieu of the between the l
seals leakage rate test currently required by the TS. The changes were requested due to practical limitations in the emergency escape airlock door hardware that prevent meaningful door seal pressure testing.
The February 20,1997, letter provided cla,ifying information within the scope of the original application and did not change the NRC staff's initial proposed no significant hazards considerations determination.
2.0 BACKGROUND
The licensee has provided the following background information.
2.1 Descriotion of Emeraency Escape Airiock The emergency escape airlock was designed and installed prior to the August 1971 issuance of Appendix J (the proposed rule was published in August 1971; the final rule was published in February 1973). The airlock consists of a steel cylinder with circular doors at each end interlocked so that only one door can be open at any time. The airiock is designed to withstand all containment conditions with either door or both doors closed. The doors open towards the interior of containment and the door directly in contact with the containment atmosphere is designated as the inner door.
- Double gaskets or seals are provided to seal each door. The seal material currently in use is an ethylene-propylene-diamine-monomer (EPDM), which has been selected because of its combined properties of resistance to radiation, sealing capability, and resistance to high temperatures. The airlock barrel may be pressurized to test its leak tightness without pressurizing the containment building. The escape lock doors each have two latching pins centered at the top and bottom of the &or (corresponding to 12 o' clock and 6 o' clock positions).
9710100232 970930 PDR ADOCK 05000255 P
o The emergency escape airlock door latching pins serve only to position the door against the stationary bulkhead. The door's design relies on the increase in containment pressure duiing a postulated event to provide sufficient closing force to produce an effective seal. The two latching pins by themselves do not provide an adequate circumferential closing force to allor j
meaningful door seal pressure testing.
4 2.2 Descriotion of Present Surveillance Test i
During c design-basis accident, the pressure applied to the doors forces them against the seals. During airlock pressure testing, a strongback (structural bracing) is necessary to I.
- simulate this pressure on the inner door and to protect the inner door locking pins from the forcer generated by the intemal test pressure in the barrel. The use of a door strongback to complete between-the-seals testing or full airlock pressure testing (inner door only) is required and was part of the original design of the doors. This design does not permit F
unrestrained between-the-seals testing.
J Past TS surveillance testing for both the personnel airlock and the emergency escape airlock.
has shown that testing at contcinment design pressure with strongbacks in place causes the seals to take a set that reflects the shape of the seal grooves. With strongbacks installed or j
test pressure applied, the male portion of the door seal (the seal bead) will be pressed
- approximately three-eighths of an inch into the seal. Thb seal will remain in this compressed condition for a 12-to-24-hour period while the test is being performed, causing the seal to take a set in the seal groove of the airlock bulkhead. After completion of the full pressure e
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test, the doors must be opened to remove the stiongback and to verify seal contact with the door seal bead in order to ensure that the seals rebound to their pre-test condition. Seal l
adjustment (" fluffing') may be required after testing 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
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on the doors further into the seal groove than obtained with normal door closure forces.
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Past test performances have shown tct once the strongbacks are removed, the seals may j
not completely rebound to their pre-test position. After full pressure testing of the airlock, a seal contact chec'< is performed as part of the surveillance test. If the seal contact check j
reveals gaps, seal adjustment is performed to ensure that the seal material rebounds to its pre-test condition. The licensee considers seal adjustment a normal part of restoration from j
testing and it is controlled by procedure.
The asal contact check consists of applying a thin layer of grease on the seal face and then closing and reopening the airlock door. This will result in a pattem in the grease that is representative of the door seal bead mating with the seal. If the grease pattem does not show adequate contact, the seals are adjusted in the area of the gap. This is done by lifting the seals slightly out of their groove so that the seal expands to its pre-test position.
Following adjustment, a final seal contact check is performed to verify the integrity of the sealing surface. The practice of verifying acceptable seal contact following performance of the airiock leak test and the acceptance criteria for this verification have been incorporated into the maintenance program.- This practice has proven to be effective through successful results during Integrated Leakage Rate Tests (ILRTs) and 6-month full airlock pressure tests.
Similarly, positive results from post-test seal adjustments have also been obtained with the
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- personnel airlock door, although an unrestrained between-the-seals test can be done and therefore is perforrned on those doors as a final test.
2.3 Descriotion of Proposed Technical Specification ChaQggs The licensee W.roposed to revise TS 4.5.2 to allow performance of a seal contact check in lieu of an unrestrained between the seals test for the emergency escape airlock doors. The licensee also proposed changes to clarify the pressure requirements for the personnel airiock doors between the seals test.
The following TS 4.5.2 test requirements, acceptance criteria, and corrective action requirements for local leak detection tests would be revised by the licensee's proposal:
l a.
Ital (1)
Local leak rate tests shall be performed at a pressu e of not less than 55 psig.
(2)
Local leak rate tests for checking air lock door seals within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> of each door opening shall be performed at a pressure of not less than 10 psig.
- b.
Acceptance Criteria (2)
The leakage for an air lock door seal test shall not exceed 0.023 L,.
c.
Corrective Action (3)
If air lock door seal leakage is greater than 0.023 L., repairs shall be initiated immediately to restore the door to less than specification 4.5.2.b(2)...
The licensee has proposed to revise these requirements'to read as follows:
a.
Ig11 (1)
Local leak rate tests, other than Personnel Airlock doors between the seals tests, shall be performed at h 55 psig.
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4 (2) local leak rate tests for checking air lock door seals within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> of
- each door opening shall be performed as follows:
(a)
A between the seals test shall be performed on the Personnel Alriock at k 10 psig.
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(b)
A full pressure test shall be performed on the Emergency Escape Airlock at h 55 psig. A seal contact check shall be performed on the Emergency Escape Alriock following each full pressure test. Emergency Escape Airlock door opening, solely for 'he purpose of strongback removal and performance of the seal contact check, does not necessitate additional pressure testing.
b.
Acceotance Criteria (2)
The leakage for a Personnel air lock door seal test shall not exceed 0.023 L,.
(3)
An acceptable Emergency Escape Airlock door seal contact check consists of a verification of continuous contact between the seals and the sealing surfaces.
c.
Corrective Action (3)
If the Personnel airlock door seal leakage is greater than 0.023 L., or if the Emergency Escape Lock door seal contact check fails to meet its acceptance criterion, repairs shall be initiated immediately to restore the door seal to the acceptance criteda of specification 4.5.2.b(2) or 4.5.2.b(3)....
The proposed changes would revise the TS 4.5.2.a(1) testing requirement to clarify the existing allowance that personnel airlock doors between the seals tests may be performed at reduced pressure. The TS 4.5.2.a(2) test requirements, TS 4.5.2.b acceptance criteriacand TS 4.5.2.c corrective action requirements would be revised to differentiate between the requirements associated with the personnel airlock doore between the seals test and the proposed emergency escape airiock doors seal contact check. The licensee also proposed changes to the related TS Basis section.
5-3.0- EVALUATION The TS changes are necessary due to the original design of the emergency escape airlock.
During special testing in 1992, the licensee showed that the annulus between the door seats could not be successfully tested without the door strongback installed even at pressures as low as 2 psig. This testing, along with information from the vendor, confirms that between-the-seals pressure testing on the emergency escape airlock doors cannot be properly measured or evaluated if the door strongbacks are not installed. Similarly, the inner door does not fully seal with the reverse-direction pressure of a full airlock pressure test unless the strongback is installed.
Since the removal of the inner door strongback after pressure testing requires the outer door to be opened, a between-the-seals test of the outer door would be required by the existing TS surveillance requirement. This test would require the installation of a strongback on the
- outer ooor. Further, full pressure testing or the pressure induced by the strongback may.
cause the seals to take a set.' It is therefore necessary to open both doors (one at a time) after any pressure testing to ensure full seal contact, and there is a potential need to readjust the seals to restore seal contact.
As an altemative to the final between-the-seals pressure test required by the TS for l
verification of door seal functionality, the licensee has proposed a final door seal contact verification. This seal performance verification is completed following the full pressure airiock l
test, after the removal of the inner door strongback, and just prior to final closure of the airlock doors. The requested TS changes would not affect compliance with the present requirement to perform a full pressure emergency escape airlock test at 6-month intervals. It would also not 3ffect the requirement to perform a full piessure emer0ency escepe airlock test within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> of opening either door during periods when containment integrity is required. The seal contact check replaces the pressure test required by the TS for the door opening (s) and/or seal adjustments associated with restoration from the required full pressure tests (i.e., the licensee has proposed to continue the practice oescribed above under Section 2.2, Descriotion of Present Surveillance Test).
- The licensee has performed additional low pressure betwean-the-seals testing on the emergency escape airlock door seals to measure seal leak rates at iow initial pressures and without the door strongbacks installed, to see if such tests would yield useful results. The trial tests were performed at pressures lower than the Palisades TS airiock door seals test pressure requirement of 10 psig. With the annulus between the door seals pressurized to as low as 2 psig without the door strongback installed, the test pressure still dropped off immediately. This indicates that the leak rates for between-the-seals testing on the emergency escape aiock cannot be property evaluated against meaningful acceptance criteria if the door strongbacks are not installed.- Therefore, meaningful between-the-seals testing is not possible with the present design of the escape airlock, without strongbacks installed.
During its review, the staff questioned whether post-test seal adjustment or '" luffing" was necessary because the door seals were too old or wom out to rebound properly to their original shape after leakage rate testing or whether past fluffing had damaged the seals, such that replacement of the seals could result in acceptable between-the-seals testing. The p
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-- licensee's response, dated February 20,1997, stated that the seals are replaced soproximately every 3 years and that the seals have not exceeded their service lives. Also, the licensee stated that fluffing has not damaged the seals, as indicated by continued successful Type B tests on both the emergency escape alriock and on the personnel airlock, on whose seals " fluffing"_ is also performed.
The performance of the door seal contact check has led to the successful completion of subsequent emergency escape airlock full pressure tests since the procedural practice began in 1987. Also, no ILRT in that period has failed because of emergency escape airlock door seal leakage. Based on these results, the airlock doors have been proven to function as designed using current methods of testing and maintenance, including ceal contact checks.
The seal contact check performed on the emergency escape airlock door seals ensures the doors are sealing properly.
Based on the abovc evaluation, the staff concludes that the licensee's proposal, to perform seal contact testing instead of between-the-seals leak rate testing on the emergency escape airlock door seals under the circumstances described above, is acceptable. Therefc e 'he
-staff finds that the proposed TS changes are acceptable.
L During review of the proposed amendment the staff identified two existing typographical j
enors in the TS. These errors were discussed with the licensee and corrected in the revised TS pages. TS 4.5.2.c(1), which reads in part, "...is not completed with 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />...," was corrected to read, "...is not completed within 46 hours5.324074e-4 days <br />0.0128 hours <br />7.60582e-5 weeks <br />1.7503e-5 months <br />...." The last Bases paragraph on page 4-23, which reads in part, "...last surveillance inspection, and investigation shall...," was corrected to read, "...last surveillance inspection, an investigation shall...." These are editorial changes that are acceptable to the staff.
4.0 STATE CONSULTATION
L in accordance with the Commission's regulations, the Michigan State official was notified of
. the proposed issuance of the amendment. The Michigan State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
The amendment changes surveillance requirements. The staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase
- in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration and there has been no public comment on such finding (62 FR 8795). Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
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! 6.0 CONCt.USION The Commission has concluded, based on the consideratione discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such actN?.ies wi!! be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor: J. Puisipher Date:
Septanber 30,1997 4
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