ML18057A829

Application for Amend to License DPR-20,changing Tech Specs Section 4.5.2a(2) & 4.5.2b(3)

ML18057A829
Person / Time
Site:	Palisades
Issue date:	03/25/1991
From:	Hoffman D CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:
Shared Package
ML18057A828	List: ML18057A827 ML18057A829 ML18057A830
References
NUDOCS 9104010393
Download: ML18057A829 (6)

Text

CONSUMERS POWER COMPANY Docket 50-255 Request for Change to the Technical Specifications License DPR-20 For the reasons hereinafter set forth, it is requested that the Technical Specifications contained in the Provisional Operating License DPR-20, Docket 50-255, issued to Consumers Power Company on October 16, 1972, for the Palisades Plant be changed as described in Section I below:

I. Changes A. Change section 4.5.2a(2) to include the following:

a. A full airlock test of either the personnel airlock or the emergency escape airldck is not required following door openings to remove strongbacks or to perform a seal contact check.

b. A seal contact check shall be performed on the emergency escape airlock doors in lieu of a reduced pressure between the seals test following door openings for strongback removal. Further testing of the emergency escape ~irlock is not required following verification of an acceptable seal contact check.

B. Add section 4.5.2b(3) as follows:

(3) An acceptable seal contact check consists of a grease bead pattern running continuously around the length of the seals.

II Discussion The above Technical Specifications change is requested to accurately describe the testing requirements and acceptance criteria currently practiced with respect to personnel airlock and emergency escape lock integrity testing.

BACKGROUND 10 CFR 50, Appendix J requires, in part, that. air-locks are to be tested as follows:

a. Airlocks shall be tested at six month intervals at an internal pressure not less than containment design pressure.

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b. Airlocks opened during periods when containment integrity is required by the Plant's Technical Specifications shall be tested within three days after being opened. For air lock doors opened more frequently than once every three days, the air lock shall be tested at least once every three days during the period of frequent openings. For air lock doors having testable seals, testing the seals fulfills the three day test requirements. In the event that the testing cannot be performed at containment design pressure, the test pressure shall be as stated in the Plant's Technical Specifications. Air lock door seal testing shall not be substituted for the six month test of the entire air lock at containment design pressure.

c. The acceptance criteria for the air lock testing shall be stated in the Technical Specifications.

Personnel Airlock The personnel airlock connects the containment building with the 611' elevation of the auxiliary building. The airlock consists of a steel cylinder with doors at each end interlocked so that only one door can be open at any time. The airlock is designed to withstand all containment design conditions with either or both doors closed and locked. The doors open toward the interior of containment.

Double gaskets or seals are provided to seal each door. This permits periodic pressurizing of the space between the seals for testing the seal integrity. The seal material currently in use is an ethylene-propylene-diamine monomer (EPDM), which is the material that has been selected because of its resistance to radiation. Various grades are available that are indicative of the rebound (spongeness) characteristics of the material. The airlock barrel may be pressurized to test its leak tightness without pressurizing the containment building. For this test, strongbacks are attached to the inner door to protect the locking bars from the resulting internal test pressure.

Emergency Escape Airlock The emergency escape airlock connects the containment building with the roof of the auxiliary building at the 625' elevation. Its features are similar to the personnel airlock. Palisades' emergency escape airlock is configured to allow testing between the seals, however, the strongbacks must be installed for the between the seals test. The emergency escape airlock vendor has reviewed the deiign and determined the emergency escape airlock at Palisades would not be leak-tight for between the seals testing without the use of strongbacks. The emergency escape airlock was not originally designed for testing between the seals without test clamps (strongbacks) in place. To verify this, the TS surveillance test was temporarily revised to perform a reduced pressure between the seals test on the emergency escape airlock without strongback installation. On May 2

10, 1989, this test was performed on the emergency escape airlock after the seals had been "fluffed" and a satisfactory seal contact check had been performed. 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. These results verified that the emergency escape airlock design would not accommodate reduced pressure between the seals testing without strongbacks. A subsequent test, consisting of a full pressure between the seals test with the strongbacks installed, was satisfactorily performed to verify emergency escape airlock integrity in accordance with plant TS.

TS Surveillance Testing Past TS surveillance testing for both the personnel airlock and the emergency escape airlock has shown that testing with strongbacks in place, at containment design pressure, causes the seals to take a set that reflects the shape of the seal grooves. After strongback removal, the doors must be opened to verify seal contact with the door sealing bead in order to assure that the seals rebound to their pre-test condition. Seal fluffing is required after testing bec~use 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 surface of the door onto the outer edge of the airlock bulkhead. With strongbacks installed and test pressure applied, the door seal bead will be pressed 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 a roughly machined finish. Therefore, irregularities exist within the seating surface which results in the seal face having peaks and valleys after testing. Past test performances have also shown that once the strongbacks are removed, the seals take a set and will not completely rebound to the pre-test position. At this time a seal contact check is performed as part of the TS surveillance test. If the seal contact check fails, seal fluffing is performed to ensure that the seal material rebounds to its.pre-test condition. Seal fluffing is considered permanent restoration of the seals and is controlled by approved Plant procedures. If large areas of the seal fail the seal contact check, the doors are adjusted to latch tighter against the seals.

NOTE:

The allowance to open an airlock door for post test restoration without further testing was believed to be acceptable, based on an August 13, 1982 conversation between Consumers Power and the NRC Project Manager for Palisades. The participants recognized the need for the outer door to be opened after completion of the full airlock test to remove the strongbacks installed on the 3

inner door and the result was an agreement that this may be done without further testing.

SEAL CONTACT CHECK The seal contact check consists of applying a thin layer of grease on the seal face and then closing and reopening the airlock door. The properties of the grease are such that it will demonstrate a pattern that is representative of the door seal bead mating with the seal. Acceptance criterion for the seal contact check is an acceptable grease bead pattern running continuously around the length of the seals. If this criterion is not met the seals are fluffed in the area of the gap, causing the seals to rebound to their pre-test position. Following fluffing, 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 airlock leak test and the acceptance criterion for this verification have been incorporated in this change request.

Palisades has proven the success of the seal contact check program on the personnel airlock. The personnel airlock design does allow for a reduced pressure between the seals test without strongbacks. This test is conducted in accordance with 10 CFR 50, Appendix J, III.2.(b)(iii).

Following successful seal contact checks, leakage results are typically less than 70 cubic centimeters per minute. Prior to 1986, the personnel airlock doors experienced an average between the seals test leak rate of 255 cubic centimeters per minute.

SUMMARY

Between the seals tests on the personnel airlock following personnel entries that occur between the required full airlock test consistently meet the acceptance criteria. The between the seals tests are successful because the problem with irregularities on the bulkhead seal groove causing the seals to take an irregular set does not occur with normal door opening and closing. Therefore, the seal fluffing is not required.

Based on the success of the between the seals tests on the personnel airlock following seal contact checks, we believe that the analogy can be drawn that the integrity of the emergency escape airlock door seals can be shown by successful performance of the seal contact check, even though a between the seals test cannot be performed because of the emergency escape airlock design. Therefore, we plan to continue to use the present methods of testing the emergency escape airlock. This includes a full pressure airlock test every six months or after door openings followed by strongback removal, seal contact checks and seal fluffing when necessary.

Analysis of No Significant Hazards Consideration The proposed TS changes do not involve a significant increase in the probability or consequences of an accident previously evaluated. This 4

determination is made because the leak test, the between the seals test and the seal contact check provide reasonable assurance that the airlock doors will act as designed to maintain containment integrity. Procedures are established to test seal integrity with the strongbacks in place and seal surface contact area following strongback removal. Acceptance criteria are established for each evolution. Failure of any of these tests would result in corrective action. Subsequent repairs must meet the previously mentioned acceptance criteria resulting in no significant increase in the probability or consequences of an accident previously evaluated.

This change has no effect on engineered safety systems and therefore the consequences of an accidents are not changed.

The proposed TS changes do not create the possibility of a new or different kind of accident from any previously evaluated. The maintenance activities described in this TS change do not require additional or new plant equipment nor do they modify installed plant equipment. As such, no change in the plant configuration results which would create the possibility of a new or different kind of accident.

The proposed TS changes do not involve a significant reduction in the margin of safety. Implementation of the test requirements and the acceptance criteria will assure that containment integrity with respect to the airlocks is maintained, therefore, there will be no reduction in the margin of safety with respect to plant operation.

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III. Conclusion The Palisades Plant Review Committee has reviewed this Technical Specification Change Request and has determined that this change does not involve an unreviewed safety question. Further, the change involves no significant hazards consideration. This change has been reviewed by the Nuclear Safety Services Department. A copy of this Technical Specification Change Request has been sent to the State of Michigan official designated to receive such Amendments to the Operating License.

CONSUMERS POWER COMPANY To the best of my knowledge, information and belief, the contents of this Technical Specification Change Request are truthful and complete.

By ~sf] ~_...___-r--t-.

David P Hoffman, Vic esident Nuclear Operations Sworn and subscribed to before me thiso<~>>f day of ~~ 1990.

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£;_,4 1 111~ £ .$llEl/£¢Notary Public Jackson County, Michigan My commission expires ;o/3 / /93 6