ML20086F473
| ML20086F473 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom, 05000000 |
| Issue date: | 12/23/1975 |
| From: | Cooney M PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | Boyd R US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML19289B554 | List: |
| References | |
| NUDOCS 8312270086 | |
| Download: ML20086F473 (2) | |
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w h %@i;f'f%ghs' December 23, 1975 14 Re:
Docket No. 50-277 Cl G
Mr. Roger S. Boyd Acting Director Division of Reactor Licensing Of fice of Nuclear Reactor Regulations United States Nuclear Regulatory Comission Washington, DC 20555
Dear Mr. Boyd:
Subject:
Unusual Event - Unit 2 Reactor Pressure Vessel Stabili zers Slight Deformation The following information was discussed with Mr. Wait",'B.aunackS
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Region 1, Of fice of Inspection and Enforcement, United States Nuclear Regulatory Comission on November 25, 1975 This information is con-sidered an unusual event and is being reported in accordance with Section 6.7.2.B of the Technical Specifications, Appendix A of DPR-44 for Unit 2 Peach Bottom Atomic Power Station.
The reactor vessel stabilizers are disc spring-type assemblics including spacer blocks installed on a rod which fits through a stabilizer bracket lug attached to the vessel. There are eight stabilizer bracket lugs attached to the reactor vessel at evenly spaced locations around the vessel below the flange. The stabilizers are attached to each bracket lug and were pretensioned during initial installation. The stabili zer ends connect to bumper brackets welded to the top of the reactor shield wall. The stabilizers are designed to provide lateral stability to the upper portion of the reactor vessel while permitting radial and axial vessel expansion, to limit horizontal vibration and to resist seismic and Jet reaction forces.
On November 23, 1975, during an inspection of the upper portions of the drywell with Unit 2 reactor in a cold shutdown condition, two of the eight reactor vessel stabilizers appeared to have been slightly deformed. Following removal of insulation from the stabilizer bracket lugs, a detailed inspection was n.ade and measurements were taken in order to transmit information to the vessel supplier for analysis.
The deformed stabilizer assemblies were located at 135 and I
315 azimuth on the vessel. Some spacer blocks were found to be rotated
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between 300 and 45 from the as-installed position. The stabilizers 1
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