ML19262C683
| ML19262C683 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 01/09/1980 |
| From: | Herbein J METROPOLITAN EDISON CO. |
| To: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| IEB-79-21, NUDOCS 8002150395 | |
| Download: ML19262C683 (6) | |
Text
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Yle-Metropolitan Edison Company Post Office Box 180 gj Middletown, Pennsylvania 17057 117 944-4041 Wnter's Direct Dial Nuncer January 9, 1980 GQL 1573 TLL 013 Mr. B. H. Grier, Director Office of Inspection and Enforcement Region i U. S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, Pa.
19406
Dear Sir:
Three Mile Island Nuclear Station Unit I (TMI-1)
Operating License No. DPR-50 Docket No. 50-289 I & E Bulletin 79-21 Enclosed please find the response to I & E Bulletin 79-21 " Temperature Effects on Level Measurements".
Sincerely, h
J. G. Herbein Vice President Nuclear Operations JGH:LWH: hah Enclosure 000215o.5 9 5 Metropohtan Ecson Comoany is a Member of the General Pubhc Utst:es System
s Enclosure RESPONSE TO IE BULLETIN 79 TEMPERATURE EFFECTS ON LEVEL MEASUREMENTS Action 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 informatien.
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
Pressurizer, Core Flood Tank and Steam Generator Level are the three liquid level measuring systems inside containment. These measuring systems are of the delta pressure, open column, uninsulated reference leg type with the exception of the core flood tank level indication. The core flood tanks that have a dry reference leg are not affected by the containment environment.
None of these systems initiate safety action (RPS or ES).
The Pressurizer and Steam Generator level measurement will be useful for PAM (post accident monitoring).
The pressurizer low-low level condition is interlocked with its heaters so that the heaters de-energize on this condition.
The steam generator level (via ICS) is utilized to control the EFW flow.
Manual control of the EFW flow, independent of the ICS, is also available in the control room.
Action 2.
On those systems described in Item I above, evaluate the effect 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 Tables 1 and 2 of Enclosure 1.
RESPONSE
The effect of the reference leg temperature on the level measurement instru.
mentation systems identified above is listed in Tables 1 and 2.
The errors listed have been maximized to account for varying fluid pressures.
Consideration has been given to boiling in the reference leg and the ejection of water from the reference leg due to the effervescence of soluble gases.
These effects will be discussed for each component employing a water reference leg.
Steam generator level measurements are not significantly affected by the effervescence of soluble gases because there is insufficient soluble gas in the secondary system. For boiling to occur in the steam generator reference leg, the reference leg must experience high temperatures and almost complete depressurization. The repressurization of the steam generator will refill the reference leg and the errors would be no greater than those listed in the tables.
e RESPONSE TO BULLETIN 79-21 The pressurizer level could be affected by tha effervescence of soluble gases.
The ejection of water from a reference leg has been documented in BW-4689 and previous 1v discussed with the NRC. A depressurization from 2000 to 1000 psi will cause an error of approximately 1%.
Larger errors can exist for rapid depressurization to less than 600 psi, but under these conditions, pressurizer level is unimportant.
However, supplementary instructions will be provided to make the operator aware of thc possibility of pressurizer level indication errors following a rapid depressurization to pressures less than 600 psi. For boiling to occur in the reference leg, the system pressure must be below 300 osi and therefore need not be considered as discussed above.
Action 3.
Review all safety and control setpoints derived from level signals to verify that the setooints 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
No reactor protection system actions are initiated by these instruments; therefore, the error induced by the increaJe in the reference leg temperature need only be considered for post-accident monitoring.
During post-accident monitoring, level indication alone is not relied upon but rather system temperature and pressures are used to assure adequate core cooling and to confirm the adequacy of the level indications.
Although not related to RPS actions, the pressurizer level instrumentation is used to deenergize the pressurizer heaters and therefore this action may have to be taken manually in the event of elevated containment temperatures.
The pressurizer and steam generator (OTSG) level setpoints are as follows:
A.
Pressurizer level control setpoints 1.
80 inches -- heater cutoff 2.
Pressurizer level control -- variable, set by operator B.
OTSG level control setpoints 1.
30 inches -- Emergency feedwater control following loss of main feedwater.
2.
50% -- Emergency feedwater control following loss of all 4 RC pumps.
Action 4.
Review and revise, as necessary, emergency procedures to include specific information obtained from the review and evaluation of Items 1, 2 and 3 to ensure that the operatorr are instructed on the potential for and magnitude of erroneous level signals.
All tables, curves, or correction factors that would be applied to post-accident monitors should be readily available to the operator.
If revisions
a RESPONSE TO BULLETIN 79-21 to procedures are required, provide a completion date for the revisions and a completion date for operator training on the revisions.
RESPONSE
We will be revising our emergency procedures to include the information obtained from the evaluation of Items 1, 2 and 3.
The revised procedures will be completed prior to TMI-I startup.
The revisions will be made in conjunction with information obtained from B&W.
Operator training on the revisions to the procedures will also be completed prior to TMI-I restart.
a TABLE 1 Correction to indicated water level for post-accident temperature effects of the steam generator operate level, steam generator full range level, and pressurizer level.
Correction to Reference leg temperature indicated level (%) of (OF) full span 100 2.0 150 3.0 200 5.0 250 7.0 300 9.0 350 12.0 400 15.0 Note: The increase in reference leg temperature causes the measured level to indicate higher than actual level.
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TABLE 2 Correction to indicated water level for post-accident temperature effects on the steam generator start-up level.
Correction to Reference leg temperature indicated level (%)
( F) of full span 100 2.0 150 3.0 200 5.0 250 8.5 300 12.0 350 16.5 400 21.0 Note: The increase in reference leg temperature causes the measured level to indicate higher than actual level.
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