ML19347C775
| ML19347C775 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 08/11/1975 |
| From: | CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | |
| References | |
| UE-4-75, NUDOCS 8102170065 | |
| Download: ML19347C775 (1) | |
Text
f.
k, UNUSUAL EVENT REPORT Big Rock Point Plant 1.
Report No: UE h-75, Docket 50-155 2a.
Report Date: August 11, 1975 2b.
Occurrence Date. July 25, 1975 3.
Facility: Big Rock Point Plant 4.
Identification of Occurrence: Control Rod Drive E h Withdrav Failure 5
Conditions Prior to Occurrence: Plant at power operation and daily rod drive exercise being conducted.
6.'
Description of Occurrence: Routine rod drive exercising at 0100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> on July 25, 1975 revealed that E-h drive would not withdraw properly. The drive was at its fully withdrawn Position 23 at the start of the test.
After repeated efforts to move the drive in a withdrawal direction proved unsuccessful, it was valved out at Position 19 preventing normal insertion while still permitting normal cooling and scram capability. Drive E h insert capability was demonstrated and the failure was verified via the routine rod exercise testing as being limited to E-h and not indicative
('
of a general drive system problem.
7 Designation of Apparent Cause of Occurrence: Unknown, although previous aymptoms of this type are indicative of a small foreign object being lodged between the drive index tube and the internal vessel drive housing.
8.
Analysis of Occurrence: The insertion from Positions 23 to 19 slightly changed the core peaking; however, the current MAPLHGR limits were not exceeded based on subsequent analysis. Since all other drives are fully operable and the shutdown margin criteria has not been compromised, we feel that no undue hazard exists for this deficiency.
9 Corrective Action: The drive will be tested at a convenient outage to determine the failure mechanism. The drive selector valve inlet and outlet valves have been closed and caution-tagged.
10.
Failure Data: Not applicable at this time due to uncertainties of failure mechanism.
(
f/0A/7666r-