ML17318A443
| ML17318A443 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 11/05/1979 |
| From: | Hunter R INDIANA MICHIGAN POWER CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| IEB-79-21, NUDOCS 7911230040 | |
| Download: ML17318A443 (14) | |
Text
INDIANAl MICHIGAN POWER" COMPANY P. O. BOX iB B0 wl.I N G G R E EN STAT ION NEW YORK, N. Y. 10004 November 5,1979 AEP:NRC:00271 Donald C.
Cook Nuclear Plant Unit Nos.
1 and 2
Docket Nos. 50-315 and. 50-316 License Nos.
Response
to IE Bulletin No. 79-21 Mr. James G. Keppler, Regional Director U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region III Glen Ellyn, Illinois 60137
Dear Mr. Keppler:
The attachment to this letter contains the information requested in IE Bulletin No. 79-21 concerning the effects of containment temperature on safety-related level monitoring systems.
The item numbers utilized in our response correspond to those used in the Bulletin.
As the information contained herein is being submitted in response to a written request for information by the NRC staff, IMPCo interprets 10 CFR 170 as requiring that no fee accompany this submittal.
Very tr ly yours, RSH:em nter Vice President'C:
R. C. Cal 1 en G. Charnoff R. S. Hunter R.
W. Jurgensen D. V. Shaller - Bridgman
L
ATTACHMENT TO AEP:NRC:00271
RESPONSE
TO IE BULLETIN NO. 79-21 "TEMPERATURE EFFECTS ON LEVEL MEASUREMENTS"
- 1 A
Res onse to Item No.
1 The liquid level monitoring systems inside containment used to initiate safety functions or to provide post-accident monitoring information are the Steam Generator Narrow-Range Water Level (SG Level) and Pressurizer Level (PZR Level) systems.
The SG level reference leg is a conventional condensing pot open
~
column system cogtained entirely within the lower volume of the con-tainment.
The PZR level high side reference leg is a sealed bellows type filled with distilled water and is contained partially in the lower volume and partially in the upper volume of the containment.
The PZR level low side reference leg is a conventional open column system entirely contained, in the lower volume of the containment.
Res onse to Item 'No.
2 The effects of post-accident temperatures on the indicated versus actual water levels have been evaluated.
These effects are shown in the attached tables.
,The biases shown in"these tables account for the heatup of the level system reference legs and the resulting change in reference leg fluid density at various system pressures.
The effect of boiling or flashing in the reference leg has been evaluated by'Westinghouse.
on a generic basis for ice condenser plants,.
such as the Cook Plant, which have spray capability in the lower.
containment volume.
The results of the Westinghouse evaluation show that reference leg boiling will not occur.
Res onse to Item No.
3 Two safety actuation functions are derived'from the'SG narrow-range level monitoring system.
The "SG Level Low-Low" setpoints were modified from 11K to 15/ and from 17K to 215 of narrow-range iastrument span for Unit Nos.
1 and 2, respectively.
These setpoint modifications were completed during unit outages in J&e, 1979.
The level bias associated with reference leg heatup is of insufficient magnitude to have any adverse effects during periods of high SG water level operation.
The 4X increase in the "SG Level Low-Low" setpoints are based on an evaluation performed by Westinghouse.
The Westinghouse evaluation shows that the peak containment temperature prior to Containment pressure reaching the "Containment Pressure-High" setpoint is approximately 200 F.
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As stated by Westinghouse in their 10 CFR 21 report, the only design basis event for which "SG Level Low-Low" is the initiating signal is the Feedwater Line Rupture.
It should be pointed out that several other trip setpoints might be reached prior to "SG Level Low-Low",
such as: "Pressurizer Pressure-High" (not assumed operable in the safety analysis for "calculational convenience"),
"Containment Pressure-High",= and Differential Pressure in Two Steam Lines-High". It should also be noted that the peak containment temperature of 328oF shown on Table No.
1 corresponds to an instantaneous double-ended rupture of a main steam pipe.
'he peak containment temperature follou~ing a Feedwater Line Rupture would be somewhat less than 328oF.
Furthermore, in an Ice Condenser containment, temperature peaks are of short duraction due to the large heat removal capability of approximately two and one-half million pounds of ice.
The "Pressurizer Level High-High" function is part of the Reactor Protection System logic.
- However, no credit was taken for this actuation function in the. safety analyses and no setpoint revisions are necessary.
An acceptable range of indicated Pressure Level has been established to accommodate the level bias discussed herein..
Adherence to these limits will assure that the pressurizer heaters remain covered and that the pressurizer does not go water solid.
Res onse to Item No.
4 The operators have been informed of the potential for non-conservative bias in indicated water level due to increased containment temperature.
The existing procedures governing maintenance of SG level following an accident are adequate and have not been revised.
The procedures.
governing maintenance of PZR level have been revised to incorporate the limits discussed above..
No further procedural revisions'are planned.
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0 TABLE 1 Correction to indicated water level for Reference Leg Heatup effects due to post-accident containment temperatures.
Containment Temperatures QF
~f Pressurizer Units 1 8.2 Steam-Generator Unit 2 Unit 1
Correction to Level X S an 120 213 280 328
- 0.45
- 4.3
- 8.1
-10.68
-. 0.45
- 4.4
- 8.65
-11.65 0.45 4.5
- 8.75
-11.77 Basis:
Calibration Pressure sia Cal ibrati on Temperature
~Rf.
R F
Height of Ref.
Leg X Level S an Pressurizer Steam Generator Unit 1 Unit 2 2250 758 830 90 106 106 1'.0058
.Notes:
Maximum Limitin Condition for 0 eration Containment Temperature g
P Containment Temperature at which Reactor Trip is -Initiated R
Highest Containment Temperature for Oouble-Ended Steam Line Break f
A 0
P 4f y t
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TABLE 2 Corrections to allowable indicated pressurizer water level for Reference Leg Heatup and Pressure changes following a high-energy line break.
Indicated Pressurizer Pressure Psia Minimum Allowed Indicated Level
%of San
'aximum Allowed Indicated Level' X of S an 10 Min. to 10 Da s After
~10 0a s
500 1000 1750 2500 5.'4 5.'4, C
3.6 0.0 3.9 3.9 2.0 0.0.",
- 4.0
-. 4.0
-, 4.0
- 4.0 Basis:
Calibration Pressure Calibration Temperature 1
Height of Ref". Leg Maximum Temperature
F 2250 psia gooF 1.0058 X. 'Level Span 10 min. to 10 days 168 After 10 days 116 Notes:
Safety'alve Actuation Pressure To Maintain Level Above Heaters
-To Prevent Actual Water Level Causing Water-Solid Conditions
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TABLE 3 Correction to allowable indicated steam generator water level for Reference Leg Heatup and Pressure changes following a high-energy line break.
Indicated Steam Generator Pressure Psia Minimum Allowed Indicated Level
~
%of San Maximum Allowed Indicated Level' X of S an
- 10 Min.'o After
~1D ih
~10 Da s Unit 1/Unit 2 Unit 1/Unit 2 15 100 500 1100 2.5/2.5 4.0/4.0 2.5/4.0 0.0/0.0 0.5/0. 5 2.0/2.0 0.5/2.0 0.0/0.0
- 4.0
- 4.0
- 4.0
- 4.0 Basis:
Calibration Pressure
- psia Calibration Temperature.
F Height of Ref.
Leg x Level Span Unit 1 758
. 106 Unit 2 830 106
'aximum Temperature oF 10 Min.to) 168 10 Days
)
After 10 Days,
. -116 168 116 Notes:
5 Safety Valve Actuation Pressure To Maintain Water Level Above Tube Sheet d
To Prevent Actual Water Level Causing Water-Solid Con&tions
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