ML20042G871

Ro:On 900412,groundwater Level Reading Taken from Dewatering Well 8 Exceeded 109 Ft Mean Sea Level Design Basis.Caused by Incorrect Level Sensor Probe Setting.Probe Adjusted Using New Setpoint Data to Cycle Dewatering Well at 108.4 Ft

ML20042G871
Person / Time
Site:	Grand Gulf
Issue date:	05/08/1990
From:	Cottle W SYSTEM ENERGY RESOURCES, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
AECM-90-0083, AECM-90-83, NUDOCS 9005160208
Download: ML20042G871 (2)

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f .U.S.' ' Nuclear- Regulatory Connission 'g Mail-Station P1-13e

,WashingtonE D.C. .~20555;  ;

Attentionse Document Control Desk i' q

'1 Gentlemen: ' N

SUBJECT:

. Grand-Gulf Nuclear Station

' Unit 1-DocketINo. 50-416:

License No.'NPF-29: 4

.High. Groundwater Elevation : '

AECM-90/0083-On April 12,E1990, a groundwater l level reading takenlfrom-dewatering; we'll-8 ' indicated 109.4 feet Mean . Sea ;I.evel1(MSL): which exceeded the 109.0 feet MSL design basis ( ' The' level-. increase was; apparently1 due' to an' incorrect ll level' sensor probe' setting'.. The probe has been properly-adjusted:using new- J

-setpoint data to cycle the dewatering well pump on at'108.4 feet MSL:and off'

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at 106.5 MSL.  :

A previous occurrence of:high groundwater level: elevation reported by O letter. dated April 16, 1990/(AECM 90/0062) required' temporary replacement ofi d I

a level sensor cable.- The temporary cable was replacedJon April-.20,L 1990-with an original equipment-type cable and the.well was restored 1to normal;

]j service. The. occurrence of high= groundwater elevation 11s. reported as- j

l. requested by your letter dated August'19, 1985 (MAEC 85/0284). l.

l 'An engineering study was performed'.in'1985 to-determine thel sensitivity of Grand Gulf Nuclear Station (GGNS)' Unit'l buildings to'a. maximum i

groundwater elevation of 114.5 feet MSL. The study. concluded that the 'l i

i- structural integrity of the Unit 1 buildings would not be: impaired. :This:

information was previously submitted by letter dated February 14, 1985-(AECM-85/0035). . - - -

7 i j Yours truly,-

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U.S. Nuclear Regulatory Commission _

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