ML20247K789

Safety Evaluation Supporting Amends 23 & 4 to Licenses NPF-68 & NPF-81,respectively

ML20247K789
Person / Time
Site:	Vogtle
Issue date:	09/12/1989
From:	Office of Nuclear Reactor Regulation
To:
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ML20247K704	List: ML20247K698 ML20247K789
References
NUDOCS 8909220019
Download: ML20247K789 (5)

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UNITED STATES y-g NUCLEAR REGULATORY COMMISSION 7;

y WASHINGTON, D. C. 20555

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ~

q RELATED TO AMENDMENT NO. 23 TO FACILITY OPERATING LICENSE NPF-68 AND AMENDMENT NO. 4 TO FACILITY OPERATING LICENSE NPF-81 GEORGIA POWER-COMPANY, ET AL.

I DOCKET NOS. 50-424 AND 50-425 V0GTLE ELECTRIC GENERATING PLANT, UNITS 1 AND 2

1.0 INTRODUCTION

By letter dated May 9,1989, Georgia Power Company, et al., requested a change to the Technical Specifications (TS) for Vogtle Electric Generating Plant (VEGP),

i Units 1 and 2.

The proposed change revises the action and surveillance requirements j

of. TS 3/4.6.1.6, " Containment Structural Integrity" and its bases.

Additional information was submitted by letters dated July 28 and August 14, 1989.

These submittals enlarged the pool of containment tendons subject to lift-off surveillance. testing, added action requirements, and changed the format of the TS to be more like the NRC standard TS. These changes did not substantially affect the amendment request as noticed or the staff's initial determination; j

therefore, the request for amendments was not renoticed.

l 2.0 EVALUATION The Vogtle Plant, Units 1 and E containments are of prestressed concrete. The i

TS include a number of surveillance requirements to ensure that the structural i

integrity of the containments will be maintained in accordance with the safety j

analysis requirements for the life of the plant.

The structural integrity of the prestressed concrete containment relies mainly on the prestressing tendon system which consists of ungrouted tendons, anchorages, i

bearing plates and grejse for corrosion protection of the system.

In order 1

to ascertain the continual integrity of the tendons in the containment, a I

l representative sample of tendons is examined at predetermined intervals. Su rveil-lance requirements include verification of tendon lift-off forces and stresses, tensile strength tests of tendon wire samples, examination of the grease samples 1

for its chemical composition and measurement of grease taken out and refilled, and visual inspection of tendon anchorages and exposed interior and exterior j

containment surfaces for any abnormality.

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The original TS has three limiting conditions for operation (LCOs) for tw two j

units. LC0(a) requires the plant to be in bot standby if the lift-off forces of Unit 1 are below the predicted limit and cannot be restored to the required yf

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a level of integrity within 15 days for Unit 1 and within 90 days of completion of Unit 1 evaluation for Unit 2.

LC0(b) requires the plant to be in hot standby if deficiencies are found in the properties of the tendon and grease and cannot be restored within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for Unit 1 and within 90 days of completion of Unit I evaluation for Unit 2.

LC0(c) requires all other parameters if found to be deficient, be restored to the required level of integrity within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or the plant be in hot standby.

The licensee requested a number of changes to the TS. The most significant of these requested changes and their bases as given by the licensee are as follows:

1. Revise " Restore the containment to the required level of integrity within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />" to " Restore or verify the containment structural integrity within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />" in LCOs (b) and (c).

Basis:

LCOs (b) and (c) refer to issting and visual inspection of components such as grease, anchor heads, shims, bearing plates and concrete. When a certain condition such as discoloration of grease or presence of minor corrosion on a shim or bearing plate exists, it may not be possible to restore the component to its original state within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

Yet, such conditions do not have an imediate impact on the containment structural capability.

In most of these instances, the imediate containment capability can be verified without immediate restoration to the original condition.

If such verification is provided, unnece.csary shutdown can be avoided.

2. Revise the detensioning requirement from all sample tendons to one tendon of each type.

Basis: Complete detensioning of a sample tendon is not necessary to determine if a tendon is defective and that dismantling and retensioning causes potential damage to the tendon and therefore should be minimized.

This finding was reflected in the proposed revision 3 to Regulatory Guide 1.35 which requires complete detensioning of only one tendon from each type.

Therefore, the requirement to detension all tendons has been revised to require that only one tendon of each type be detensioned.

3. Modify retensioning requirements to ensure no overstressing of strands and to reconcile the difference in measuring points for tensioning load and elongation between TS stipulation and actual installation.

Basis: TS requirements for retensioning can cause conflict between the specified lift-off force and the desire not to tension the tendon at greater than 70% guaranteed ultimate tensile strength (GUTS).

Reconciliation of measuring points for load and elongation will allow better comparison.

4. Revise the end anchorage and adjacent concrete surface inspection requirements such that they may be performed during tendon surveillance rather than Type A testing.

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. Basis:

Internal pressure at ILRT will not affect significantly the condition at end anchorages and adjacent surfaces. Therefore, it does not justify the additional cost to perform the inspection at ILRT rather than at tendon surveillance.

5. Other changes are to reflect the requirements applied to two units, the characteristics unique to the prestressing tendon system used at Vogtle ano the provision of specific acceptance criteria.

The NRC staff reviewed the licensee's requested change to the TS and found the licensee had incorporated some of the features of the NRC staff's Standard Technical Specifications (STS).

However, the origir.al TS had deficiencies which were not corrected by the proposed change.

The deficiencies are:

1. Tendon lift-of f is only performed on Unit 1, and visual inspection is conducted on Unit 2 for the life of the plant.

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2. The LCOs are more stringent on abnormalities of components such as grease, anchor heads, shims, bearing plates and concrete than on those of the lift-off forces.

3. There is no consideration of any action if the average of all measured prestressing forces for each group is found to be less than the minimum required.

4. There is no consideration of any action if the trend of prestress loss is larger than expected and the resulting prestressing forces will be less than the minimum required for the group before the next scheduled surveillance.

It is to be noted that at the time of licensing, the Vogtle TS represented the NRC staff's STS.

Licensees of plants of similar vintage as Vogtle with nearly the seme TS hau been requesting relief from the TS requirements.

In view of this fact, the NRC staff prepared a new STS which incorporates the experiences learned from the surveillance of containment tendons. The new STS alleviate stringent LC0 requirements and correct the deficiencies in the surveillance requirements.

The NRC staff informs licensees requesting changes to TS that they can adopt the new STS with some modifications to fit each unique condition.

The licensee of Vogtle was informed of this choice and followed it.

In Vogtle the VSL Corporation prestressing tendon system has been used.

In this system the tendons consist of strands instead of wires and the anchorage system consists of cones and wedges.

At the time of construction, it was decided that tendon surveillance for Unit I would involve the lift-off and detensioning of tendons and that for Unit 2 would require only visual inspection.

The new 1

STS requires lift-off and visual inspection to be alternated between the two units for consecutive intervals of surveillance.

For Unit 2 tendcns, lift-off can be done but detensioning to take strand samples and retension would be very difficult.

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- To resolve this, the licensee proposed to perform lift-off testing on Unit 2 and detension one tendon on Unit 1 and remove a tendon strand sample for material testing.

The revised TS include the option of demonstrating that containment integrity 'is maintained as opposed to restoring the nonconforming tendons to the required level of integrity when a measured or observed parameter falls outside its acceptance criteria for both the LCOs set out below, and retaining the 72-hour LC0 to be applied, if the average of all measured prestressing forces from the sample group fall outside the acceptance criteria. All other measured or observed parameters identified in the surveillance requirements would fall within a 15-day LCO. This 15-day LC0 would also be applied to a requirement to perform trending analysis of prestressing forces.

If the trending analysis predicts unacceptable values, it will be considered as an indication of abnormal degradation and additional testing will be required to determine the cause and extent of such degradation. The LC0 will be applied to both units if a problem should be identified on one unit.

The revised TS was agreed upon after a number of telephone calls with the licensee.

The licensee's submittal of August 14, 1989 formalized this agreement.

Based upon this discussion and evaluation, the NRC staff has concluded that:

(1) the TS meet the NRC staff's STS requirements for containment vessel structural integrity; and (2) the TS are consistent with and support the conclusions of the original Safety Evaluation.

The proposed changes to the TS are, therefore, acceptable.

3.0 ENVIRONMENTAL CONSIDERATION

These amendments involve changes in surveillance requirements. The staff has determined that the amendments involve 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 exposure.

The NRC staff has made a determination that the amendments involve no significant hazards consideration, and there has been no public comment on such finding. Accordingly, the amendments meet the eli criteria for categorical exclusion set ferth in 10 CFR 51,22(c)(9)gibility Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.

4.0 CONCLUSION

The Commission made a proposed determination that the amendments involve no significant hazards consideration which was published in the Federal Register on June 14, 1989 (54 FR 25374), and consulted with the state of Georgia. No public comments were received, and the state of Georgia did not have any comments.

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9 The staff has concluded, based on the considerations 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, and (2) such activities will be conducted in complicnce with the Commission's regulations, and the issuance of these amendments will not be inimical to the common defense and security or to the health and safety of the public.

Principal Contributors: Jon B. Hopkins, PDil-3/DRP-1/II C. P. Tan, ESGB/ DEST Dated:

September 12, 1989 l

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