ML19259D353
| ML19259D353 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 09/17/1979 |
| From: | Counsil W CONNECTICUT YANKEE ATOMIC POWER CO. |
| To: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| NUDOCS 7910180189 | |
| Download: ML19259D353 (13) | |
Text
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Y:k-s CONNECTICUT YANKEE AT O M I C POWER COMPANY BERLIN. CONNECTICUT P
O. BOX 270 H ARTFO RD. CONN ECTICUT 06101 Tats >=ons 203-666-6911 September 17, 1979 Docket No. 50-213 Mr. Boyce H. Grier, Director Region I Of fice of Inspection and Enforcement U. S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA 19406
Reference:
(1)
B. H. Grier letter to W. G. Counsil dated August 13, 1979, transmitting I&E Bulletin No. 79-21.
Gentlemen:
Haddt m Neck Plant Temperature Ef f ects on Level Transmitters, I&E Bulletin No. 79-21 Reference (1) requested Connecticut Yankee Atomic Power Company (CYAPCO) to review the liquid level measuring systems within containment, in particular, to:
(1) Determine if signals from these systems are used to initiate safety actions or provide post-accident monitoring information and, if so, provide a description of such systems.
(2)
Evaluate the effect of post-accident ambient temperatures on the indicated water level as measured by those systems identified in Item (1).
(3) Review all safety and control setpoints derived from level signals to verify that the setpoints will initiate the action required by the plant safety analysis throughout the range of ambient temperatures, including accident conditions, encountered by the instrumentation.
(4) Review and revise emergency procedures, if necessary, to ensure that operators are instructed on the potential for and magnitude of erroneous level signals.
In addition, the NRC Staff requested that this information be submitted within 30 days from the date of Reference (1).
CYAPCO hereby provides the responses to Items (1) through (4) of I&E Bulletin No. 79-21 as Attachment (1). CYAPC0 has reviewed the level measurement error, resulting from reference leg heat up, with respect to the Haddam Neck Plant FDSA and determined that no safety actuation signal setpoint changes are necessary since the actual level measurement at the maximum gc:t 1165 180 g 1910180 9
. containment temperature is bounded by current safety analyses.
In addition, no credit is taken for the low steam generator level / flow mismatch trip in the Haddam Neck Plant FDSA during transients where high containment temperatures exist which could cause level measr.rement errors.
CYAPCO trusts this information is responsive to your requests and satisfactorily dispositions the Reference (1) concerns.
Very truly yours, CONNECTICUT YANKEE ATOMIC POWER COMPAh7 M. G.$ ounsil Vice President Atta ctnent W
By:
W. F. Fee Vice President 1165 181
DOCKET No. 50-213 ATTACifMENT (1)
HADDAM NECK PLANT I&E BULLETIN No. 79-21 TDiPERATURE EFFECTS ON LEVEL TRANSMITTERS bO SEPTEMBER, 1979
Itee (1)
Review the liquid level measuring systems within containment to determine if the signals are used to initiate safety actions or are used to provide post-accident monitoring information.
Provide a description of systems that are so employed ; a description of the type of reference leg shall be included, i.e., open column or sealed reference leg.
Response
Each steam generator has a narrow range and a wide range level measuring system.
The narrow range system utilizes a differential pressure (D/P) transmitter to produce a signal proportional to the level in the steam generator. This signal is recorded on the main control board and is also input into the Reactor Protection System (RPS) logic.
A reactor trip is initiated upon low steam generator water level coincident with a feedwater-steam flow mismatch (feedwater flow 20% less than steam flow).
This system also provides post-accident monitoring information. The narrow range trans-mitters are calibrated with consideration given to normal temperature. The reference leg of the system is of the open-column type.
The wide range level measuring system also ut.11zes a D/P transmitter and is utilized for post-accident monitoring information. The signal is recorded on the main control board. The wide range level measuring system is calibrated for cold conditions and utilizes a reference leg of the opea-column type.
The Pressurizer has four (4) level measuring systems which utilize D/P trans-mitters to derive the level signals. The signals are recorded on the main control board and are also input to the RPS logic (two out of three). A reactor trip is initiated upon high pressurizer level only. These level measuring systems are also utilized for post-accident monitoring information. These four level measuring systems are calibrated with consideration given to normal temperature and are designed with a reference leg of the open-column type.
The pressurizer also has one level measuring system calibrated to cold conditions.
The signal is derived by a D/P transmitter and recorded on the main control board.
This system provides post-accident monitorinc information in the event the four level measuring systems calibrated with respect to temperature are inoperative. This system utilizes an open-column reference leg.
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. ltem (2)
On those systems described in Item (1) above, evaluate the ef fect of post-accident ambient temperatures on the indicated water level to determine any change in indicated level relative to actual water level. This evaluation must include other sources of error including the effects of varying fluid pressure and flashing of reference leg to steam on the water level measurements.
The results of this evaluation should be presented in a tabular form similar to TabJes 1 and 2 of Attachment 1.
Response
Analyses have shown that the maximum containment temperature for the worst case accident is 260 F and carrections to level measurements from both the steam generator and pressurizer for temperatures up to and including 260 F are included ir. Tables 1 - 6.
Corrections to measurements f ron the cold calibrated wide range level instruments (due to reference leg heatup) for both the steam generator and pressurizer are not required on the basis that these systems do not initiate any safety actions.
Item (3)
Review all safety and control setpoints derived from level signals to verify that the setpoints will initiate the action required by the plant safety analyses throughout the range of ambient temperatures encountered by the instrumentation, including accident temperatures.
Provide a listing of these setpoints.
Response
CYAPCO has reviewed all safety and control setpoints derived from level measuring devices and determined that no revisions are necessary based on the following.
A low steam generator water level measured by the narrow range level instru-mentation coincident with feedwater/ steam flow mismatch initiates a reactor trip.
Analysis has shown that for a high energy line break, a reactor trip is actuated by high containment pressure. The containment temperature is calculatec _o be less than 200 F at the time the high containment pressure trip is initiated.
The normal operating water level is 30% (25.50 inches above the lower tap) and the low level setpoint is 10% (8.5 inches above the lower tap). At a containment temperature of 200 F, the level measurement error, including 1 3trument error, is 6% of span (5.10 inches), and the low level setpoint would become 4% (3.40 inches above the lower tap).
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. Analyses of the loss-of-feedwater flow outside containment, addressed in Section 10.3.6 of the Haddam Neck Plant FDSA, were performed with the low level trip setpoint at both 10 inches and 40 inches below ncrmal.
(Normal water level in this analysis was 50%.) These limits correspond to a band from 2.5 - 32.5 inches above the lower tap.
Ihe dif ference in the results of the analyses was negligible.
Since the actual setpoint value of 3.40 inches, at the limiting containment temperature, is within analyzed limits, CYAPCO has determined that no low steam generator water level setpoint changes are necessary.
The pressurizer is equipped with three (3) temperature compensated level measuring systems which will trip the reactor, with two out of three logic, at a high level setpoint of 86%. Upon initiation of the high containment pressure trip with a containment temperature of 200 F, the level measuring system in the pressurizer will indicate a water level 3 - 7% too high, depending on instrument error. The reactor trip will then be initiated at a high level setpoint of 79 - 83% above normal water level which is more conservative.
Item (4)
Review and revise, as necessary, emerger.cy procedures to include specific information obtained from the review and evaluation of Items (1 ), (2),
and (3) to ensure that the operators are instructed on the potential for and magnitude of erroneous level signals. All tables, curves, or correction factcrs t hat would be applied to post-accident monitors should be readily available to the operator.
If revisions to procedures are required, provide a completion date for the revisions and a completion date for operator trait.1. g on the revisions.
Response
CYAPCO will review and revise, as necessary, all Emergency Operating Procedures by October 1, 1979, to take into account measurement errors resulting from reference leg heat up, ' _ocess variable changes and instrument error. The information presented in Tables 1 - 6 will be used to revise post-accident monitoring level limits to envelop the most conservative conditions.
All oper;; ors will complete training on the revisions by the same date.
In addition, a caution statement will be included in the Emergency Operating Procedures, informing the operator to make use of several plant indicated variables (due to the poselbility of erroneous level indications caused by neasurement errors) to verify the levels in the steam generators and 65
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. pressurizer. The operators are also cautioned to not rely upon steam generator and pressurizer water level indications in any depressurized system following a high energy line rupture inside containment since there exists the possibility of reference leg boiling.
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TABLE 1 Correction to indicated steam generator narrow range water level for Reference Leg Heatup effects due to post-accident containment temperature (before reactor trip).
Maximum Containment Temperature Correction to S/G Level Reached Before Reactor Trip, F
% of Span 120 0
180 3
200 4
220 5
240 6
260 7
Basis:
Assumed Level Calibration Pressure = 690 psia.
Assumed Reference Leg Calibration Temperature = 120 F.
Inst rument Error Adds +2% to Correction Correc-ion will be applied so as to 'ower the indicated level.
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TABLE 2 Corrections to allowable indicated steam generator narrow range water level for Reference leg Heatup and Pressure changes following a high-energy line break, to assure that true level is between the level taps.
Containment Correction to Minimum Allowed Correction to Maximum Allowed Temperature, F Indicated Level, % of Span Indicated Level, % of Span 120 3
-6 180 6
-6 2'00 7
-6 220 8
-6 240 9
-6 260 10
-6 Basis:
Assumed Level Calibration Pressure = 690 psia.
Assumed Reference Leg Calibration Temperature = 120 F.
50 psia Pressure 931 psia.
2% Instrument Error is included in corrections.
Boiling in the Reference Leg will not occur unless the steam generator pressure drops below saturation pressure for the temperature in the reference leg.
Steam generator pressure would have to decrease to less than 35.4 psia for boiling to occur if the -reference leg is at 260 F.
In determining the Correction to Maximum Allowed Indicated Level, thermal lag is taken into account. The most conservative case at maximum level is when containment temperature increases but the reference lag temperature remains at 120 F.
In determining the Correction to Minimum Allowed Indicated Level, the most conservative case is to assume the reference leg temperature increases immediately.
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TABLE 3 Corrections to allowable indicated steam generator wide range water level for Reference Leg Heatup and Pressure changes following a high-energy line break, to assure that true level is between the level taps.
Containment Correction to Minimum Allowed Correction to Maximum Allowed Temperature, F Indicated Level, % of Span Indicated Level, % of Span 120 6
-26 180 8
-26 2q0 9
-26 2'20 10
-26 240 11
-26 260 11
-26 Basis:
Cold calibration 50 psia Pressure 931 psia.
2% Instrument error is included in corrections.
Boiling in the reference leg is not assumed.
In determining the Correction to Maximum Allowed Indicated Level, thermal lag is taken into account. The most conservative case at maximum level is when contaiament temperature increases but the reference lag temperature remains at 120 F.
In determining the Correction to Minimum Allowed Indicated Level, the most conservative case is to assume the reference leg temperature increases immediately.
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TABLE 4 Correction to indicated pressurizer water level (calibrated with consi-deration given to temperature) for Reference Leg Heatup effects due to post-accident containment temperature (before reactor trip).
Maximum Containment Temperature Correction to Pressurizer Level Reached Before Reactor Trip, F
% of Span 120 0
180 4
200 5
220 6
240 8
260 10 Basis:
Assumed Level Calibration Pressure = 2020 psia.
Assumed Reference Leg Calibration Temperature = 637 F.
1000 psia Pressure 2285 psia.
Instrument error adds +2% to correction.
Correction will be applied so as to lower the indicated level.
I16o
! 51 0
TABLE 5 Corrections to allowable indicated pressurizer water level (calibrated with consideration given to temperature) for Reference Leg Heatup and Pressure changes following a high-energy line break, to assure that true level is between the level taps.
Containment Correction to Minimum Allowed Correction to Maximum Allowed Temperature, F
Indicated Level, % of Span Indicated Level, % of Span 120 6
-9 180 9
-9 2'd0 10
-9 220 12
-9 240 13
-9 260 15
-9 Basis:
Assumed Level Calibration Pressure = 2020 psia.
Assumed Reference Leg Calibration Temperature = 637 F.
2% Instrument error is included in corrections.
Boiling in the Reference Leg will not occur unless the pressurizer pressure drops below saturation pressure for the temperature in the reference leg.
Pressurizer pressure would have to decrease to less than 35.4 psia for boiling to occur if the reference leg is at 260 F.
In determining the Correction to Maximum Allowed Indicated Level, thermal lag is taken into account. The most conservative case at maximum level is when containment temperature increases but the reference leg temperature remains at 120 F.
In determining the Correction to Minimum Allowed Indicated Level, the most conservative case is to assume the reference leg temperature increases immediately.
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TABLE 6 Corrections to allowable indicated pressurizer water level (cold calibrated) for Reference Leg Heatup and Pressure changes following a high energy line break, to assure that true level is between the level taps.
Containment Correction to Minimum Allowed Correction to Maximum Allowed Temperature, F Indicated Level, % of Span Indicated Level, % of Span 120 13
-43 180 15
-43 2Q0 16
-43 2'20 17
-43 240 17
-43 260 18
-43 Basis:
Cold calibration.
1000 psia Pressure 2285 psia.
2% Instrument error considered.
Boiling in the Reference Leg is not assumed.
In determining the Correction to Maximum Allowed Indicated Level, thermal lag is taken into account. The most conservative case at maximum level is when containment temperature increases but the reference leg temperature remains at 120 F.
In determining the Correction to Minimum Allowed Indicated Level, the most conservative case is to assume the reference leg temperature increases immediately.
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