ML17207A443
| ML17207A443 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 09/18/1979 |
| From: | Robert E. Uhrig FLORIDA POWER & LIGHT CO. |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| NUDOCS 7910050236 | |
| Download: ML17207A443 (7) | |
Text
P 0 BOX 529100 MIAMI FL 33152 FLORIDA POWER & 1.1GHT COMPANY Sept~ 181979.
'1 CD
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~ r Mr. James P. O'Reilly, Director, Region II Office of Inspection and Enforcement U.
S. Nuclear Regulatory Commission 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303
Dear Mr. O'Reilly:
Re:
RII:JPO 50-335 IE Bulletin 79-21 Florida Power
& Light Company has reviewed the subject Bulletin and a response is attached.
Very truly yours, Robert E. Uhrig Vice President Advanced Systems
& Technology REU/DKJ/ms Attachment cc:
Director, Office of Inspection and Enforcement Harold Reis, Esquire V91005D Z3W:
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CC C
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ATTACHMENT
RESPONSE
TO IEB 79-21
~R I
A review of liquid level measuring systems located within the St..'..Ludie Unit 1
containment has -concluded that only two such systems either initiate safety actions or provide post-accident monitoring information.
These systems measure the levels contained in the press'urizer and the steam generators.'Both systems use 'level transmitters of a differential pressure type utilizing open column reference legs with condensing pots.
The pressurizer has two level transmitters which are used for control and indica'tion purposes only.
Each 'steam generator has six level transmittters.
Two are used for control.and indication purposes and the remaining four initiate safety action (Low steam generator water level trip signal) as well as providing level indication.
~R2
'Post-accident ambient temperatures differing from the design operating val'ue will induce errors in the water levels indicated in the control room.
Increased reference leg temperatures will cause a decreased reference column density which will in turn cause a higher indicated 1'evel than is actually pre'sent in the
~
associated vessel (steam generator or. pressurizer).
A tabular presentation of this temperature effect is provided in Tables 1
5 2 (attached).
The maximum containment temperature calculated for the most severe accident (LOCA) is 259'F.
Level errors can als'o.be induced by,pressure changes within the pressurizer. or steam generators due to the effect on the size of steam bubbles entrained in the saturated
. fluid contained in these vessels.
Evaluation of the dynamic effects of rapid pressurization or depressurization requires complex calculations for ea'ch individual case.
Static effects have been determined for various pressures and are provided
. as Figures 1 and 2.
Flashing of reference leg fluid is' third potential source of error in leyel indication.
Flashing could cause rapid'f1uctuations of large magnitude in the reference leg fluid level resulting in large errors in indicated leyel.
Fop both the p'ressurizer and the steam generators, a rapid and very large depressurization would be required in order for flashing to occur in the reference legs.
Assuming a'eference leg temperature of 260'F (maximum, postulated containment temperature is, 259'F),
fl'ashing would not be expected to occur until pressure reached approximately 35 psia.
A reactor trip'ould be initiated long before this'ressure is reached either by
'the Thermal Margin/Low Pressure trip function (1735 psig minimum pressurizer pressure) or the Lo& Steam. Generator Pressure trip function (485 psig minimum steam generator pressure).
\\
Page 2
.~3*
3 A review of the St. Lucie Unit 1 safety analyses indicates that the low steam generator level trip is required to initiate a safety action only for the excess load transient and the loss of normal feedwater flow cases.
As neither of these cases involve a high energy break within containment, they would have no effect on indicated Tevel.
As stated previously,.pressurizer level is not uti3ized to initiate any safety action.
It is concluded that no setpoint changes are required.
Res onse 4
Emergency procedures are. undergoing review and revision to incorporate the information provided in Responses 1, 2, and 3.
All licensed operators, will be instructed on the potential for level errors as described by the bulletin.
All figures and tables provided as the response to this bulletin will be readily available to the operators in the control room.
Procedure changes will be completed by October 31, 1979, and operator training will be completed by t/ovember 30, 1979.
',TABLE 1
CORRECTIONS TO INDICATED STEAN GENERATOR LEVEL
~
DUE TO REFERENCE LEG HEAT-UP Containment Temperature oF 100 200 250 280 300 Induced Error X of Span 0
+ 4.6
+ 7.8
+ '9.9
+11.4 BASIS:
Level calibration temperature
= 100'F Level calibration pressure
< 900 psia Reference leg effective height
< 1.1 x level span
TABLE 2 CORRECTIONS TO INDICATED PRESSURIZER LEVEL DUE TO REFERENCE LEG HEAT-UP Containment
, Temperature oF 100 200 250 280 300 Induced Error 5 of Span 0
+ 6,8
+11.4
+14.6
+16. 8 BASIS:
Level calibration temperature
= 100'F Level calibration pressure
< 2250 psia Reference leg effective
< 1.1 x level span
IO X IO TO THE CENTIMETER IO X 2$ CM.
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