ML19317F831
| ML19317F831 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 05/13/1975 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19317F832 | List: |
| References | |
| NUDOCS 8002210580 | |
| Download: ML19317F831 (2) | |
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SACRAMENTO MUNICIPAL UTILITY DISTPICT C 6201 S Street. Box 15830. Sacramento. California 95813 -(916) 452 3211
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May 13, 1975 Director Division of Reactor Licensing U.S. Nuclear Regulatory Commis,sior.
Washington, D.C.
20545 Re: Operating License DPR-54 Docket No. 50-312 Rancho Seco Nuclear Generating Station Unit No. One Abnormal Occurrence No. 75-9
Dear Sir:
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As defined by Proposed Amendment to the Technical Specifications for the Rancho Seco Nucicar Power Station, Section 6.9.L and Regulatory Cuide 1.16, Rev. 3, Section C.2.b.(2), we are reporting the following s
Abnormal Occurrence as A0 75-9.
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Technical Specifications Section 3.2.3 require.i.at least the equivalent of 10,000 gallons of 7,100 ppm boron in the concentrated boric acid storage tank. This quantity of boric acid in storage is sufficient to borate the reactor coolant system to a 1% subcritical margin in cold shutdown at the worst time in core life with the highest t worth control rod stuck out.
To meet this requirement, the equivalent of 7,500 gallons of 7,100 ppm boron is actually needed. An additional 2,500 gallons were added to the Technical Specifications for conserva-tism.
J On April 14, 1975, chemical cleanup of the once through steam.
generators was being conducted prior to power operation. A steam generator' excessive blowdown caused a reactor trip on high pressure.
To satisfy the shutdown margin requirement, borated water was Odded to the reactor coolant system from the concentrated boric acid storage
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tank according to established procedure. During the injection the CBAST. level was reduced to 9,500 gallons of 7,015 ppm boron.
The
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reactor was returned to critical on April 15, 1975, ar.J a routine monitor of the CBAST instrumentation revealed that the tank volume,
was not refilled to normal after the initial boron injection into the reactor coolant system. A 2,000 gallon batch of 11,500 ppm boron
.was put-into the CBAST-within approximately one hour after discovery.
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80 02 210 SPO wpY SENT REGION AN ELEC'RIC SYSTEM S E R VIN G MORE T H A N ' 6 0 0. 0 0 0 tN THE-HEAR' 0F C A Lif 0 R N l A t
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Director Division of Reactor Licensing
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May 13, 1975 To prevent reoccurrence of this event, thu " Process Standards
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Procedure" will be revised to require a minimum volume of 20,000 gallons of 7,100 ppm boron. The extra volume will provide the necessary bora-l tion to meet the shutdown requirbments and have sufficient capacity to meet the Technical Specification limits for return to critical.
This abnormal occurrence will also be covered in the operator retraining i
i that will be performed for A0 75-7.
There was no transient associated with this Abnormal Occurrence.
Respectfully,
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[d.dJ. Mattimoe Assistant General Manager
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and Chief Engineer i
Enclosure cc:
R. H. Engelken, Region V 1
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