ML19262A269
| ML19262A269 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 09/11/1975 |
| From: | METROPOLITAN EDISON CO. |
| To: | |
| Shared Package | |
| ML19262A265 | List: |
| References | |
| 75-06, 75-6, NUDOCS 7910260601 | |
| Download: ML19262A269 (2) | |
Text
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ENCLOSURE Metropolitan Edison Company Three Mile Island Nuclear Station Unit 1 (IMI-1)
Docket No. 50-289 Operating License No. DPR-50 Non-Routine 30-Day Report 75-06 1.
Description of Deficiency The results of the annual hydrographic survey for TMI-1 (see pages 2-24 and 2-25 of the TMI-l Final Safety Analysis Report for a description of the survey) showed that an excessive amount of sediment had accumulated in the intake channel since it was last dredged.
(This channel was created to provide the station with adequate cooling water for emergency shutdown under conditions of low river flow and failure of York Haven Dam to the south.) It was then determined from analyses performed by Met-Ed's consultants that with the present condition of the channel, not enough cooling water would be available to the station for safe shutdown during a LOCA should the following two eients occur simultaneously:
a.
a decrease of the river flow to less than 7000 cfs, and b.
f ailure of a major portion of the York Haven Dam.
The probability that all three of these events (LOCA, low riter flow, and dam failure) will occur simultaneously is exceptionally low; th ere-fore, the present condition of the Unit 1 intake channels is not con-sidered to represent a serious safety problem.
2.
Corrective Action Sho rt-Te rm Until the intake channels can be dredged, the following actions will be taken in the sequence given:
a.
The Superintendent of the York Haven Hydro Station will be instructed to insure that the Superintendent of TMI-l is notified if and when the York Haven Dam fails, b.
Should the York Haven Dam fail, we will then obtain daily river flow measurements from the Harrisburg gauging station (about ten miles upstream from Three Mile Island).
c.
Should the river flow at the Harrisburg gauging station decrease to less than 7000 cfs, we will then p.t the Unit 1 reactor into cold shutdown.
Also as a short-term action, we will proceed with our efforts to obtain an emergency permit f rom the Army Corps of Engineer and to mobilize the necessary equipment so that dredging can commence at the earliest possible date.
1484 303 4910260 O/
. Long-Term As a long-term corrective action to insure that adequate cooling water will be available, the Unit 1 intake channels.will be dredged according to specifications prepared on the basis of a postulated failure of the York Haven Dam under low-river flow conditions.
So that future situations of the present type can be avoided, the intake channel for Unit 1 will be surveyed twice (instead of once) each year, along with the intake channel for Unit 2, as part of a commitment made in the Unit 2 Final Safety Analysis Report.
In this way, undesirable sediment accumulations can be discovered and dealt with more quickly, 1484 304