ML19317D828
| ML19317D828 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 10/22/1974 |
| From: | DUKE POWER CO. |
| To: | |
| Shared Package | |
| ML19317D827 | List: |
| References | |
| NUDOCS 7912100564 | |
| Download: ML19317D828 (2) | |
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.e Duke Power Company Oconee Unit 1 Report No: A0-269/74-15 Report Date:
October 22, 1974 Occurrence Date:
October 7, 1974 Facility: Oconee Unit 1, Seneca, South Carolina Identification of Occurrence:
Failure to increase Core Flood Tank Pressure Prior to increasing Reactor Coolant System Pressure.
Conditions Prior to Occurrence: Reactor shutdown, react'or coolant temperature 250 F, pressure 400 psi.
Description of Occurrence:
On October 7, 1974 the Oconee Unit 1 Reactor Coolant System pressure was being increased in preparation for a leak test following a maintenance outage.
The Core Flood Tank pressure had been reduced from the normal pressure of 600 : 25 psi to 400 psi on October 6, 1974.
The Reactor Coolant System temperature and pressure were increased from 2500F and 450 psi at 2200 hours0.0255 days <br />0.611 hours <br />0.00364 weeks <br />8.371e-4 months <br /> to 296 F and 920 psi at 2302 hours0.0266 days <br />0.639 hours <br />0.00381 weeks <br />8.75911e-4 months <br />.
Technical Specification 3.3.3 requires that core flood tank pressure be increased to 600 t 25 psi before reactor coolant pressure exceeds 800 psi.
Reduction of Reactor Coolant System pressure cocnenced immediately and was below 800 psi before 2312.
The core flood tanks were pressurized to 600t 25 psi and Reactor Coolant System pressure was again increased to perform the leak test.
Designation of Apparent Cause of Occurrence:
A heatup and pressurization of the Reactor Coolant System of Oconee Unit 1 as specified in " Controlling Procedure for Unit Startup" was being performed.
The Control Operator was instructed to hold system te=perature to less than 3000F while increasing pressure to 2283 psi for a leak test.
The control Operator mistakenly assumed that the Precritical Checkoff for the Operating Procedure, which called for the Reactor Coolant System leak test, could be perforced out of sequence.
The procedural steps which were omitted would have insured that the core flood tanks were at the proper pressure before the unit reactor coolant i
pressure was increased above 800 psi.
Analysis of Occurrence:
The Core Flood System is designed as a passive system to provide borated water to the reactor vessel following intermediate to large Reactor Coolant System piping failures.
The amount of time necessary for the water to flow from the core flood tanks is dependent upon the differential pressure between the core flood tanks and the reactor vessel.
The pressure 600 225 psi specified for the l
core flood tanks is calculated on the basis of providing coolant to the core l
following a loss of coolant accident (LOCA) at full power 2568 FMt.
Since the reactor had been shutdown for at least forty-six hours prior to this incident the decay heat from the core would be less than one half of one percent full 79121006
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power or approximately 12.84 MNt.
Therefore, ths core flood tanks at a prassure of 400 pai along with other core coolant systems availabic during the design basis LOCA would have been more than sufficient to cool the core in the unlikely event that a LOCA had occurred during this time period.
It is concluded that the health and safety of the public was not affected.
l Corrective Action:
4 The pre-critical checkoff for the Operating Procedure OP/1/A/1102/01, " Controlling Procedure for Unit Startup", has been revised to prevent future occurrences of this type.
A note has been added which prohibits completion of steps in the Precritical Checkoff until conditions specified in the startup procedure have been satisfied.
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