ML19329C265
| ML19329C265 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 08/04/1976 |
| From: | Roe L TOLEDO EDISON CO. |
| To: | |
| References | |
| HO-1295-F3, NUDOCS 8002120979 | |
| Download: ML19329C265 (2) | |
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DAVIS-BESSE NUCLEAR POWER STATION UNIT NO. 1 REPORT ON SURVEILLANCE SPECIMEN CAPSULE HOLDER TUBE Description of the Problem The design of the reactor vessel surveillance specimen holder tubes as originally installed on the Davis-Besse Station, Unit No. 1 reactor vessel internals is described in B&W Topical Report BAR-10100A(1). This same design was installed in six (6) operating units.
During the week of Feburary 29, 1976, while attempting to remove a surveillance capsule train from its holder tube at the Three Mile Island, Unit No. 1 reactor vessel, wear to the holder tube was observed.
Subsequent inspection at this unit and of the other five (5) operating units verified that r'.are was flow-induced motion and that mechanical wear was taking place.
Evaluation The surveillance specimen capsule, holder tube and holddown mechanism do not perform a direct safety function.
Extensive wear, however, would alle parts of the assembly train to become loose parts in the annulus between the thermal shield and reactor vessel wall. The smaller of these parts could also contact the lower vessel head and lower reactor vessel internals. Damage to the reactor vessel clad, incore instrument guide tubes and lower reactor vessel internals structures could result if no corrective action were taken. This damage would not represent an imminent threat to public health and safety, but could require extensive repair to assure these structures remain serviceable for the life of the plant.
Corrective Action The originally installed three (3) surveillance specimen holder tubes have been removed from the Davis-Besse Unit No. 1.
Redesigned holder tubes have been installed in these three (3) azimuthal locations and three (3) additional tubes have been installed at new locations.
Extensive qualification testing instrumen-tation has also been installed to obtain data during the hot functional testing scheduled to start in late August, 1976.
The design of the new surveillance specimen holder tube and the proposed qualification testing program were present3d by B&W to members of the NRC staff in a meeting in Bethesda, Maryland on May 26, 1976, which was attended by a representative from Toledo Edison.
The presentations included a description of the operating experience with the original desi;n, the new design, the design analysis performed, including con' sider-acion of flot-induced vibration,,and the qualification test program to be imple-mented te verify the design adequacy. As a result of this meeting, approval was
s given to Toledo Edison to complete the installation of the six (6) surveillance specimen holders. B&W was subsequently requested by the NRC to provide additional strain gage readings during the hot functional test, which has been agreed to.
Topical Reports are in preparation by B&W describing the redesigr and the qualification program. These are scheduled for submittal to the NRC in August.
In addition, a Topical Report will be prepared by B&W documenting the results of the qualification testing and this will be submitted to NRC following completion of the hot functional test and evaluation of the data.
REFERENCE 1.
B&W Topical Report BAW-10100A, " Reactor Vessel Material Surveillance Program -
Conformance to 10 CFR 50, Appendix H, for Oconee Class Plants", February 1975.
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August 3, 1976 I
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