ML20129K073

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Proposed Tech Spec 3.6.1.6,allowing one-time Exemption to Requirements of SR 4.6.1.6.1.e.1
ML20129K073
Person / Time
Site: Byron, Braidwood  Constellation icon.png
Issue date: 11/04/1996
From:
COMMONWEALTH EDISON CO.
To:
Shared Package
ML20129J804 List:
References
NUDOCS 9611080105
Download: ML20129K073 (11)
v • d • e


Text

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a E  ; E! !! E gj g gl FIGURE 3 TENDON ARRANGEMENT IN CONTAINMENT OPENING AREA .

1 1' ATTACHMENT B-1 PROPOSED CHANGES TO APPENDIX A, TECHNICAL SPECIFICATIONS, OF FACILITY OPERATING LICENSE NPF-37 and NPF-66 BYRON NUCLEAR POWER STATION Affected Pane 3/4 6-8 kmla.byrbwd.lar:greasef. doc:

CONTAINMENT SYSTEMS i

' ' 1 CONTAINMENT VESSEL STRUCTURAL INTEGRITY LIMITING CONDITION FOR OPERATION

3. 6.1. 6 The structural integrity of the containment vessel shall be maintained at a level consistent with the acceptance criteria in Specifications 4.6.1.6.1,Y 4.6.1.6.2, and 4.6.1.6.3. l APPLICABILITY: MODES 1, 2, 3, and 4 ACTION:

a.

With more than one tendon with an observed lift-off force between the predicted 1,ower limit and 90% of the predicted lower limit or with one tendon below 90% of the predicted lower limit, restore the tendon (s) to the required level of integrity within 15 days and perform an engineering evaluation of the containment and provide a i Special Report to the Commission within 30 days in accordance with Specification 6.9.2 or be in at least HOT STANOBY within the next l i

6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. l 1

b. With any abnormal degradation of the structural integrity other than ACTION a. at a level below the_acngptance criteria _,of Specifications 4.6.1.6.1, 4.6.1.6.2, and 4.6.1.6.3, restore the containment vessel to l 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 />.and perform an engi-neering evaluation of the containment and provide a Special Report to the Commission within 15 days in accordance with Specification 6.9.2 or be in at least HOT STAND 8Y within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. l SURVEILLANCE REQUIREMENTS 4.6.1.6.1 Containment Vessel Tendons. The containment vessel tendons' struc-tural integrity shall be demonstrated at the end of 1, 3, and 5 years following I the initial containment vessel structural integrity test and at 5 year intervals thereafter. The tendons' structural integrity shall be demonstrated by:
a. Determining that a random but representative sample of at least 19 tendons (5 dome, 6 vertical, and 8 hoop) each have an observed lift-off force within predicted limits for each. For each subsequent 1

inspection one tendon from each group may be kept unchanged to develop I a history and to correlate the observed data. If the observed lift-off force of any one tendon in the original sample population lies between the predicted lower limit and 90% of the predicted lower limit, two tendons, one on each side of this tendon should be checked for their lift-off forces. If both of these adjacent tendons are found to be within their predicted limits, all three tendons should be restored to the required level of integrity. This single deficiency may be considered unique and acceptable. Unless there is abnormal degradation of the containment vessel during the first three inspec-tions, the sample population for subsequent inspections shall include

\ at least 10 tendons (3 dome 3 vertical, and 4 hoop);

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1 j ATTACHMENT B-2 PROPOSED CHANGES i TO APPENDIX A, TECHNICAL SPECIFICATIONS, OF FACILITY OPERATING LICENSE NPF-72 and NPF-77 4

i BRAIDWOOD NUCLEAR POWER STATION i

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$ CONTAINMENT SYSTENS 1

CONTAINMENT VESSEL STRUCTURAL INTEGRITY  !

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LINITING CONDITION FOR OPERATION i i i

3. 6.1. 6 The structural integrity of the containment vessel shall be maintained j

j atalevelconsistentwiththeacceptancecriteriainSpecifications4.6.1.6.1.p 4.6.1.6.2, and 4.6.1.6.3.

APPL 7CA8ILITY: MODES 1, 2, 3, and 4.

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.- ACTION:

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a. ,

i With more than one tendon with an observed lift-off force between '

'. the predicted lower limit and 905 of the predicted lower limit or i

with one tendon below 90% of the predicted lower limit, restore the tendon (s) to the. required level of integrity within 15 days and l perfom an engineering evaluation of the containment and provide a l i I Special Report to the Commission within 30 days in accordance with Specification 6.9.2 or be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

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b. With any abnomal degradation of the structural integrity other than ACTION a. at a level below the acceptance criteria of Specifications 4.6.1.6.1, 4.6.1.6.2, and 4.6.1.6.3, restore the containment vessel to 1

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 /> and perform an engi-

! neering evaluation of the containment and provide a Special Report to ,

the Commission within 15 days in accordance with Specification 6.9.2 i

f or be in at least NOT STAN08Y within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

\ SURVEILLANCE REQUIRENENTS

. 4.6.1.6.1 Containment Vessel Tendons. The containment vessel tendons' struc-tural integrity shall be demonstrated at the end of 1, 3, and 5 years following the initial containment vessel structural integrity test and at 5 year intervals
thereafter. The tendons' structural integrity shall be demonstrated by

!' a. Determining that a random but representative sample of at least 19 i tendons (5 done, 6 vertical, and 8 hoop) each have an observed lift-j ,, off force within predicted Ifmits for each. For each subsequent j

inspection one tendon from each group may be kept unchanged to develop i

a history and to correlate the observed data. If the observed Ifft-4 off force of any one tendon in the original sample population lies i

between the predicted lower limit and 90% of the predicted lower limit, two tendons, one on each side of this tendon should be checked l' for their Ifft-off forces. If both of these adjacent tendons are

' found to be within their predicted 11mits, all three tendons should ,

l be restored to the required level of integrity. This single deficiency may be considered unique and acceptable. Unless there is abnormal 1

degradation of the containment vessel during the first three inspec-i i

tions, the sample population for subsequent inspections shall include s at least 10 tendons (3 dome, 3 vertical, and 4 hoop);

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i ATTACHMENT C EVALUATION OF SIGNIFICANT HAZARDS CONSIDERATIONS FOR PROPOSED CHANGES TO APPENDIX A, TECHNICAL SPECIFICATIONS, OF FACILITY OPERATING LICENSES NPF-37, NPF-66, NPF-72 AND NPF-77 Commonwealth Edison Company (Comed) has evaluated this proposed amendment and has determined that it involves no significant hazards considerations. According to Title 10, Code of Federal Regulations, Section 50, Subsection 92, Paragraph c (10 CFR 50.92 (c)), a proposed amendment to an operating license involves no significant hazards

considerations if operation of the facility in accordance with the proposed amendment would not
1. Involve a significa at increase in the probability or consequences of an accident previously evaluated; or
2. Create the possibili:y of a new or different kind of accident from any accident previously evaluated, or
3. Involve a significant reduction in margin of safety.

A. INTRODUCTION Commonwealth Edison Company (Comed) proposes to amend Technical Specification (TS) 3.6.1.6, " Containment Vessel Structural Integrity," for Byron Nuclear Power Station, Units 1 and 2 (Byron) and Braidwood Nuclear Power Station, Units 1 and 2 (Braidwood) to allow a one-time exemption to the Technical Specification Surveillance Requirement (TSSR) 4.6.1.6.1.e.1) to allow greater than 5% of the tendon sheathing filler grease to be removed for a period of time in support of steam generator replacement on Unit 1 of each station. LomEd wishes to remove the sheathing filler grease in the tendon sheathing in up to thirty-fie tendons in advance of the steam generator replacement outages (SGROs).

The old steam generators will be removed through a contamment opening that will be created for the replacement outage. A system of prestressing tendons runs both horizontally and vertically through the containment wall. Each tendon is enclosed in tendon sheathing which has been filled with grease to prevent tendon corrosion. 'Ihe outside air temperatures during the scheduled SGROs are expected to result in increased removal forces that could result in damage to the tendons or sheathing system due to reduced grease temperature. To overcome the effect ofincreased grease viscosity on removal forces, a majority of the sheathing filler grease will be removed prior to the k nla:byrbwd.lar:greasef. doc:

SGROs. Grease removal will take place during the warm weather months to ensure that the maximum volume of grease is removed.

B. NO SIGNIFICANT HAZARDS ANALYSIS

1. The proposed change does not involve a significant increase in the probability or consequences of an accident previously evaluated.

The prestressing tendons are passive components that form part of the contamment structure. As passive components, there are no tendon failure modes that could act as accident initiators or precursors. Consequently, the proposed change to

- remove a portion of the tendon sheathmg filler grease will not increase the probability of an accident previously evaluated.

The tendons, in their passive role, function to limit the consequences of accidents  ;

previously evaluated, and their continued integrity is important to the ability of the i containment to mitigate design basis accidents. Structural degradation of the containment is a predictable process that can be monitored by a comprehensive contamment tendon monitoring program as required by Technical Specification Surveillance Requirement 4.6,1.6. The monitoring program is based on proposed Revision 3 of Regulatory Guide 1.35, " Inservice Surveillance of Ungrouted Tendons in Prestressed Concrete Contamment Structures," April 1979.

The tendon surveillances conducted at both Byron and Braidwood have consistently shown that structural integrity of the tendon system has been maintamed, including adequate corrosion protection for the tendon wires and end anchorage components, and there has been no esidence of grease leakage from the tendon sheathings. While a number of below-grade hoop tendons have shown signs of water intrusion, the tendons that will have grease removed are above-grade and are not expected to experience water intrusion.

A review of domestic nuclear facility experience found cases where large grease voids existed for periods longer than requested under the proposed change without resultant corrosion in those tendon systems. A case where tendon wires removed from a decommissioned plant were exposed to an environment more severe than expected in a sealed tendon sheath did not show signs of corrosion. These experiences demonstrate the effectiveness of the initial corrosion protection systems applied to the tendons and the effectiveness of partial grease protection in the tendon sheathmg.

Based on the above cases, it can be concluded that the removal of the filler grease (grease voids greater than 5 percent) from the tendon sheathing in up to thirty-five tendons for a limited period will not adversely affect the integrity of the tendons or the capability of the tendon system to fulfill its design basis function.

The removal process will only remove the grease not directly adhering to the tendons. The grease remaming will be adequate to protect the tendons during the relatively short period of partial grease removal. Therefore, no changes in the k:nta:byrbwd:largreasef. doc:

a tendon properties would be expected, and the consequences of design basis accidents previously evaluated will not be affected by the proposed change.

2. The proposed change does not create the possibility of a new or different kind of accident from any accident previously evaluated.

The proposed change only affects the tendon sha='hing filler grease void limits of TSSR 4.6.1.6. No new equipment is being installed and no existmg equipment is being modified. Operation with a grease void in excess of current requirements does not alter system configurations such that any new or different accidents can be initiated. Therefore, no new or different accident initiators or precursors are being introduced, and the proposed change will not create the possibility of a new or different kind of accident from any previously evaluated.

3. The proposed change does not involve a significant reduction in a margin of safety.

The margin of safety applicable to the proposed change is defined by the difference between the. design pressure of the contamment and the point at which the contamment would actually fail. The design pressure of the contamment is 50 psi. As a result of conservatisms inherent in the design techniques and in the material selections made for the Byron and Braidwood contamments, a substantial margin to failure exists in the contamment. 'Ihis margm is discussed in Subsection 3.8.1.8 of the UFSAR. It is noted therein that the ultimate capacity of the concrete shell is 125 psi, correspondmg to the initiation of yicid in the hoop post-tensioning tendons in conjunction with yielding of the reinforcement near the 3

mid-height of the containment wall.  ;

l It is also noted in Subsection 3.8.1.8 that the ultimate capacity of a contamment l electrical penetration is 108 psi. While this value is substantially greater than the I 50 psi required of the design, it is lower than the 125 psi at which failure of the containment wall section would be predicted. Therefore, tendon strength is not the limiting factor in the margin of safety inherent in the contamment.

As previously discussed, no degradation of the tendons is expected to occur as a result of the proposed TS change. Further, the tendon strength is not the limiting factor in the containment ultimate capacity, which is substantially greater than the ,

requirement placed on the contamment design by the plant design basis. l Therefore, the proposed change will not reduce the margin of safety designed into Byron and Braidwood.

Based on the above evaluation, Comed has concluded that the proposed change involves no significant hazards considerations.

k:nts:byrtmd:largreasef. doc:

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ATTACHMENT D l ENVIRONMENTAL ASSESSMENT FOR PROPOSED CHANGES TO APPENDIX A, TECHNICAL SPECIFICATIONS, OF FACILITY OPERATING LICENSES NPF-37, NPF-66, NPF-72 AND NPF-77 l

1 Commonwealth Edison Company (Comed) has evaluated this proposed license amendment request against the criteria for identification oflicensing and regulatory actions requiring environmental assessment in accordance with Title 10, Code of Federal Regulations, Part 51, Section 21 (10 CFR 51.21) Comed has determined that this proposed license amendment request meets the criteria for a categorical exclusion set forth in 10 CFR 51.22(c)(9). This determmation is based upon the following:

1. The proposed licensing action involves the issuance of an amendment to a license for a reactor pursuant to 10 CFR 50 which changes a requirement with respect to installation or use of a facility component located within the restricted area, as defmed in 10 CFR 20, or which changes an inspection or a surveillance requirement. This proposed license amendment request permits Unit 1 operation with tendon sheathing filler grease voids in excess of 5% of the net duct volume for up to 35 tendons for a limited time period;
2. this proposed license amendment request involves no significant hazards considerations as demonstrated in Attachment C;
3. there is no significant change in the types or significant increase in the amounts of any effluent that may be released offsite; and
4. there is no significant increase in individual or cumulative occupational radiation exposure.

Therefore, pursuant to 10 CFR 51.22(b), neither an environmental impact statement nor an environmental assessment is necessary for this proposed license amendment request.

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