ML19309A370
| ML19309A370 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 11/22/1974 |
| From: | SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | |
| Shared Package | |
| ML19309A367 | List: |
| References | |
| NUDOCS 8003270823 | |
| Download: ML19309A370 (2) | |
Text
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/~'N UNUSUAL OCCURRENCE REPORT
(
)
.g DOCKET NO. 50-312-74-3 Reporting Date:
November 22, 1974 Occurrence Date:
November 5, 1974 Time: 10:30 a.m.
Rancho Seco Nuclear Facility _:
Generating Station Unit No. 1 Clay Station, California Identification of Occurrence:
Discharge of effluent water containing high dissolved solids.
Condition Prior to Occurrence:
The reactor was at cold shutdown conditions to perform minor maintenance on the turbine throttle valves.
Description of Occurrence:
Plant liquid effluents not within specific limits when The contents of the being released are diverted to one of two retention basins.
retention basins are then held until a sample can be obtained and analyzed for When the contents of the effluent are known, an Effluent Release chemical content.
Data Form is completed describing the conditions.in which the effluent may be released and the form is signed by a specific representative from the Technical and Operating Groups.
On November 4, 1974, at 2240, a sample was obtained from the South Basin that had a conductivity of 6080 umho/cm.
The release limit in Appendix B of the Technical Specifications, Section 2.3A, is 850 mg/L which corres-To reduce the conductivity within the limits ponds to 1200 umho/cm conductivity.a factor of 5 dilution was required on the release for discharge to the environment, Thus, on 0030, November 5, 1974, a vaste release flow of 1000 GPM was form.
This overdilution was conservative and initiated with a 10,500 GPM dilution flow.
The shifts were resulted in a conductivity release well below the specified limit.
changed at_0800 and an inspection that morning of the high dilution rate and a check of the release' form indicated that the dilution could be reduced to 4,000 GPM with The flow changes were performed at approximately a waste discharge of 800 GPM.
time the monitoring instruments were indicating within the discharge 10:15 and at that The operator left the liquid release area and assumed c.her operating i
limits.
"letention A short time later, an alarm sounded in the control room indics-
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duties.
Basin Trouble". The operator returned to th'e release area at 12:15 and noco:cd th' conductivity recorder was above the limit. He increased the dilution 11 an.
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effluent dischargt was 12:30 the conductivity was reduced below 1200 paho/cm.
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terminated at 1305.
8003270d[>M '
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,s Corrective Action Taken or Which Should be Taken:
4 The design of the retention basins is presently being reviewed by SMUD Engineering. Several additions and modifications are contemplated, olie of which would install a recirculating system on each basin.
The recirculation would prevent obtaining poor representative samples, as described in this report under " Analysis of Occurrence".
Designation of Apparent Cause: Design.
Analysis of Occurrence:
Effluents diverted to the retention basins contain various j
chemicals, including aci'ds and basics used for regeneration of demineralizers.
The different chemical solutions tend to stratify in the basins during holdup. With the strata and the necessity of obtaining manual samples while standing on the sloping sides of the basin, a representative sample is difficult to obtain. The sample obtained November 4, 1974 was not representative of the conductivity of the waste solution. Since the discharge with a dilution of 10,500 GPM was below the
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j 1200 pmho/cm discharge limits the conductivity could not have exceeded 3150 pmho/cm during the 4000 GPM discharge between 10:30 and 12:30 when the conductivity recorder j
was off scale: The site Plant Review Committee determined that discharging 3150 paho/cm '
j at 4000 GPM for two hours would not have any detrimental effects on the environment.
1 j
Equipment I.D.:
Not applicable.
I Failure Data:
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Non-representative samples have been obtained previous to this event. However, the dilution was adjusted to compensate for the error during the discharge.
Action Required 'to Prevent a Reoccurrence:
A recirculating system with a sample point should be-added to each basin. This system is presently under design by Generation Engineering.
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