ML20205C922
| ML20205C922 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 09/18/1985 |
| From: | Schnell D UNION ELECTRIC CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20205C927 | List: |
| References | |
| ULNRC-1173, NUDOCS 8509230356 | |
| Download: ML20205C922 (8) | |
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UNION ELECTRIC COMPANY 1901 Grotiot Street St. Louis Donald F. Schnen Vice President September 18, 1985 Mr. Harold R. Denton, Director Office of Nuclear Reautor Regulation U. S. Nuclear Regule. tory Commission Washington, D.C.
20555 ULNRC-ll73
Dear Mr. Denton:
DOCKET NUMBER 50-483 CALLAWAY PLANT UNIT 1 REVISION TO TECHNICAL SPECIFICATION 3/4.6.1.6 CONTAINMENT VESSEL STRUCTURAL INTEGRITY Union Electric herewith transmits three (3) original and forty (40) conformed copies of an application for amendment to Facility Operating License No. NPF-30 for Callaway Plant, Unit 1.
This application requests that Section 3/4.6.1.6, Containment Vessel Structural Integrity, of the Callaway Plant Technical Specifications, Appendix A to the Operating License, be revised.
The requested change revises the present Technical Specification regarding surveillance parameters and actions to be taken when a parameter which serves as an indicator of continued acceptable structural integrity falls below a level previously considered acceptable.
The revision provides for prompt attention and necessary corrective action to assure acceptable design margins are maintained for the life of the plant while eliminating the need to shutdown the plant or maintain the plant shutdown when the nonconforming parameter is shown by an engineering evaluation to not degrade the integrity of the plant.
The revision will also change the requirement to verify that the voids in the tendon sheath filler grease are less than 5% of the net duct volume, and to verify no widespread grease leakage during a visual inspectica of the containment exterior.
Enclosed is a check for the C150.00 application fee required by 10 CFR 170.21.
Very truly yours 8509230356 850918
~~
PDR ADOCK 05000483 P
pop Donald F.
Schnell RRG/drs
Enclosures:
1 - Safety Evaluation 2 - Significant Hazard Consideration 3 - Marked Specification Pages 3/4 8 and 3/4 6-9 4 - Initial Fill Void Factors Moiling Address: RO Box 149, St. Louis, MO 63166 h
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STATE OF MISSOURI )
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Donald F. Schnell, of lawful age, being first duly sworn upon oath says that he is Vice President - Nuclear for Union Electric Company; that he has read the foregoing document and knows the content thereof; that he has executed the same for and on the behalf of said company with full power and authority to do so; and that the facts therein stated are true and correct to the best of his knowledge, information and belief.
By Donald F. Schnell Vice President - Nuclear SUBSCRIBED and sworn to before me this /[- ay of
,, 1985 0 l-AM2 SARBARA [FMFF k M 8 NOTATJ FU30C, STATE 07 MIS 3 CUM MY COVxtSS10tl "cXFIRES APRIL 22,1933 ST. LCulS COUNTY.
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Gerald Charnoff, Esq.
Shaw, Pi t tman, Potts & Trowbridge 1800 M.
Street, N.W.
Washington, D.C.
20036 Nicholas: A. J Petrick Executive Director SNUPPS 5 Choke Cherry Road Rockville, Maryland :20850 G. C. Wright
- Division of_. Projects and Resident Programs, Chief, Section lA U.S.
Nuclear Regulatory Commission
. Region III j
799 Roosevelt Road Glen Ellyn, Illinois 60137 Bruce Little Callaway Resident Office 4
U.S.
Nuclear Regulatory Commission l
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Steedman, Missouri 65077 Tom Alexion
- Office of Nuclear Reactor Regulation-4
' U.S. Nuclear Regulatory Commission 1
- Mail.Stop P-316 7920 Norfolk Avenue Bethesda, MD 20014 Ron Kucera, Deputy Director Department of Natural Resources l
P.O.
Box 176 i
Jefferson City, Missouri 65102 t
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Enclozure 1 to ULNRC-1173 Page 1 of 3 SAFETY EVALUATION This amendment requer.ts the rewording of ACTION b. and the addition of ACTIONS c. and d. to S,)ecification 3.6.1.6 and the revision of surveillance Specification 4.6.1.6.1.e.1). The requested change revises the present Technical Specification regarding parameters to be surveilled and actions to be taken when a parameter which serves as an indicator of possible abnormal degradation falls below a level previous-ly considered acceptable. These actions take into account the relative importance of the indicators to actual structural integrity and assign action times accordingly.
The revision to ACTION b. provides for prompt, thorough attention and necessary corrective action to assure acceptable design margins are maintained for the life of the plant while eliminating the need to shutdown the plant when it can be shown by an engineering analysis that the nonconforming parameter does not degrade the structural integrity of the plant.
The present action statement requires that whenever any element of the tendon surveillance acceptance criteria is not satisfied, it be i
considered as evidence of abnormal degradation of the structural integ-rity of the Containment Vessel requiring that the integrity be restored or that the plant be shutdown. The proposed amendment, however, would classify a failure to satisfy an element of the acceptance criteria as evidence of possible abnormal degradation and would permit an evaluation to be performed demonstrating the continued ability of the Containment Vessel Structure to perform its design function. The proposed amendment still provides the action for the plant to shutdown if the engineering evaluation does not demonstrate Containment integrity.
The addition of Action c. provides for timely evaluation and correction of those parameters which in themselves do not indicate abnormal degradation but which may allow future degradation if not corrected. This ACTION also provides a report to the Commission describing the condition and action taken.
i The inclusion of an exemption from the provisions of Specification 3.0.4 by-adding ACTION d. reduces the impact on plant operation consis-tent with the allowable times contained in ACTION a. and ACTION b.
The revision to 4.6.1.6.1.e.1) changes the requirement to verify a specific percent void in the filler grease to verifying no widespread grease leakage during a visual inspection of containment. The tendons at Callaway Plant were initially. greased between April and October, 1981 by Inryco using current industry standard filling procedures. These procedures did not require recording the amount of grease injected into
. each sheath nor -did they require verification of 6 5% voids. At that time, Union Electric was committed to Reg Guide 1.35 Rev 2 which deals only with voids in the trumpet area and not of the entire sheath.
Revision 4 of Westinghouse Standard Technical Specifications, from which Callaway Plant made its original submittal, makes no mention of void
to ULNRC-1173 Page 2 of 3 measurement. The only method to accurately determine voids in the grease which "could be indicative of leakage in the tendon-duct system" is to assume the sheath was completely filled initially. Enclosure 4 shows that even under optimum filling conditions, voids ranging from 12-15% could be expected after the initial filling operation using current filling techniques. Subsequent tests at Callaway have provided validity for these numbers. Even for those tendons that were filled by an alternate technique, there is no direct assurance that the voids are 6 5%. Therefore, the requirement for verification of 6 5% voids is meaningless for Callaway Plant and should be deleted.
The essential criteria for the operability of the sheathing filler material is; A. to prevent corrosion of both the tendon wires and the anchorage components, and b.
to detect leakage into the concrete.
A.
Corrosion prevention is assured by adequately coating the tendon wires and the anchorage components. The molecular structure of the grease is such that it has an affinity for adhering to steel, j
specifically the tendon wires and anchorages. As long as sufficient grease has been introduced into the system to completely coat the wires and anchorages, corrosion protection is assured. Protection is afforded by each tendon wire being individually pre-coated with Amber 1601 prior to installation. The degree of filling the interstitial. spaces, which comprise the net duct volume, is not directly related to the degree of coating which occurs and, consequently, is not of significant importance as an indicator of operability of the sheathing filler material.
The Callaway Plant tendons requiring-net refill volumes of the filler material in excess of the acceptance criteria have not shown any abnormal deterioration or degradation of strength. The lift-off forces for those tendons, as well as the other surveillance tendons, have been found to fall within (or above) the predicted limits.
Examination and testing of the individual wires from tendons V74 and 26AC has revealed that there is no evidence of corrosion and that the wire strength exceeds the minimum required ultimate strength throughout the wires. Examination of the filler material has shown virtually no change in the physical appearance or chemical properties. Test results. indicate that the amount of chlorides, sulfides, nitrates, and moisture fall-far below the maximum allowed limits as specified by the manufacturer. Visual inspection of the different components of the anchorage system revealed proper coverage by the filler material with no signs of corrosion or presence of water.
The material used in the Callaway Plant post-tensioning system, Visconorust 2090P-4, accomplishes its corrosion protection function by a characteristic which gives the filler material an affinity to adhere to steel surfaces, its ability to emulsify any moisture in the system nullifying its rusting ability, and by its resistance to i
moisture, mild acids, and alkalis.
Enclosura 1 to ULNRC-1173 Page 3 of 3 As indicated by the test results referenced above, the function c:
the filler material in protecting the post-tensioning system is being maintained. Test data from other plants with longer operating history have failed to show any correlation between the amount of voids and tendon strength failures. Should this trend develop in later years on older plants, corrective action could be taken at Callaway Plant prior to any tendon degradation.
B.
In accordance.with the recommendations of proposed revision 3 to Regulatory Guide 1.35, a visual examination of the exterior surfaces of containment was made prior to the start of lift-off testing to detect areas of widespread cracking, spalling, or grease leakage.
This inspection revealed none of these problems. The procedures required to verify 6 5% voids have the potential to create the very problem they were designed to detect. In order to ensure no voids, the tendon sheaths must be abnormally pressurized. This pres-surization may create leaks which would not occur normally. Addi-tionally, complete filling of tendon sheaths have caused gasket failures in the past due to thermal expansion.
Based on the results of the first surveillance, the evaluation of results from other plants, and items A and B above, this amendment to Technical Specification 3.6.1.6 does not affect or endanger the health and safety of the general public and does not involve an unreviewed safety question.
m, ___.
Enclosura 2 to ULNRC-1173 Page 1 of 2 SIGNIFICANT HAZARDS CONSIDERATION This amendment request revises ACTION b. and adds ACTION c. and d.
associated with Technical Specification 3.6.1.6, and revises surveil-lance 4.6.1.6.1.e.1).
The iCTION Statement rewording assures acceptable design margins for the life of the plant while eliminating the need to shutdown the plant or maintain the plant shutdown when nonconforming parameters are shown by an engineering evaluation to not degrade the containment integrity. The revision to the surveillance eliminates the requirement for precise verification of a parameter that cannot be accurately determined and has adequate back up surveillance parameters to assure acceptable design margins are maintained throughout plant life.
The Safety Evaluation included as Enclosure 1 to this letter, provides Union Electric's bases for concluding that the Callaway Plant can be safely operated consistent with the revised action statement.
In evaluating the increase in probability or consequences of any previously analyzed accident, the following areas were considered:
1.
Design Conservatism The Containment Vessel post tensioning system is a passive element designed to provide a minimum level of pre-stress of 1.2 x the design accident pressure at the end of the 40 year design life of the plant. As such, there is a wide margin of safety at the beginning of the plant life which decreases to a minimum value of 1.2 at 40 years.
2.
Surveillance Frequency Periodic tendon surveillances arit required by Reg. Guide 1.35.
The first three surveillances occur ut 1.5, 3.5 and 5.5 years after the structural integrity test, and surveillances are required every five years thereafter. The length of the intervening period of 5 years between successive surveillancer is evidence of recognition of the extreme improbability of the deterioration of the post tensioning system to a level where vessel integrity would be affected in this time period. As such, there i; no basis for the requirement for restoration or shutdown within the time periods given in the Techni-cal Specification.
3.
Industry Experience This sane philosophy of evaluation to assure continued integrity has been approved by the NRC for a plant with a containment similar to the Callaway containment. Since no fundamental difference in the post tensioning systems exist which would affect this philosophy, a precedent has been established to accept this specification.
Enclorura 2 to ULNRC-1173 Page 2 of 2 4.
Surveillance Results During the initial inservice tendon surveillance at the Callaway Plant, it was discovered that net refill volumes of sheathing filler material (grease) exceeded 5 percent of the net duct volume for several tendons. These results for the affected tendons suggest that those tendon sheaths were not totally filled with grease, probably due to the characteristics of the greasing system.
The above incidences, involving net refill grease volumes in excess of the acceptance criteria, have not affected the strength of the tendons. Lift-off forces for the surveilled tendons have been found to lie within (or above) predicted limits indicating that, among other things, wire integrity has not been degraded. Examination and testing of individual wires from the tendons has revealed that there is no evidence of wire corrosion and that wire strength has not been degraded. Examination of the grease itself has revealed that there are no changes in the presence (at the anchorage) or the physical appearance of the grease and the chemical properties have been verified by laboratory analysis. As evidenced by examination of the surveillance tendons, the detected underfill conditions have not affected the ability of the grease to provide minimum coverage for the different parts of the anchorage system.
Additionally, data gathered from other plants with more operating history than Callaway have failed to show any correlation between percent voids and either lift-off force or tensile strength fail-ures.
Based on the above discussions, this change does not involve a significant increase in the probability or consequences of an accident previously evaluated.
The proposed change to the Specifications: will not impact tendon integrity since tendon integrity will be assured by surveillance of remaining parameters and restoration of parameters or assurance by engineering evaluation; vill not affect the methcd and manner of plant operation; and will not affect components and equipment important to safe operation. Thetefore, the proposed amendment does not create the possibility of a new and different accident from any previously evaluated.
The surveillances and actions requested provide assurance that any tendon degradation would be identified and corrected in a timely manner consistent with the indicators, and, therefore, this change does not involve a significant reduction in a margin of safety.
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