ML19344E976
| ML19344E976 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 08/05/1980 |
| From: | Moody D Maine Yankee |
| To: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| IEB-79-21, WMY-80-32, NUDOCS 8009120207 | |
| Download: ML19344E976 (2) | |
Text
M l
- ~
=
T MAME " N"HARHEE niMGF05'EnCCMP.202 o TURNPIKE ROAD (RT. 9)
$ gC.
ENGINEERING OFFICE WESTBORO, MASSACHUSETTS 01581 617-368-9011 J
MiY-80-32 B.4.1.1 August 5, 1980 United States.!uclear Regulatory Commission Office of Inspection and Enforcement Region I 631 Park Avenue King of Prussia, Pennsylvania 19406 Attention:
Mr. Boyce H. Grier, Director
References:
(a) License No. DPR-36 (Docket No. 50-309)
(b) USNRC Letter to MYAPC dated August'13, 1979, Re:
IE Bulletin 79-21 (c) MYAPC Letter to YSNRC dated September 14, 1979 Re:
Response to IE Bulletin No. 79-21
Dear Sir:
Subject:
Additional Response to IE Bulletin No. 79-21 Reference (c) provided a response to Items 1, 2 and 3 of Reference (b).
Response to Item 4 of Reference (b) was deferred pending a review of a potential situation which could cause additional errors in indicated level systems which went beyond the scope addressed in IE Bulletin No. 79-21.
This letter provides the response to Item 4 of Reference (b) and additionally describes a condition which could increase the magnitude of error of indicated level systems during accident / post accident situations.
IE Bulletin No. 79-21 addressed the concern of erroneous level indications which could result during an accident / post accident situation as a reuslt of increased temperatures of the reference leg of various level indicators. The increase in tcmperature of the reference leg causes a decrease in reference leg de..sity and, therefore, changes the calibration correction factor for the level system.
However, the calibration shift of a level transmitter due to density changes are not limited to the reference leg alone. A density change of the variable leg will also cause the same type of error to be introduced into the indicated system level.
l 8009120ZOE G
U.S. Nuclear Rsgulatory Commission August 4, 1980 Attention:
Mr. Boyce H. Grier, Director Page 2 Typical level indicating systems used during normal operating conditions are calibrated' assuming specified conditions of temperature (density) for both the reference leg and the variable. During normal operations, minor changes in either temperature have negligible effects on the indicated level as compared to actual level.
During or after an accident, however, there may be signifcant differences in the conditions of both the reference leg and the variable leg.
For example:
Following a small break LOCA, it could be hypothised that the pressurizer may have emptied and then, following safety injection, refilled with significantly colder reactor coolant system and safety injection system water.
At the same time, the containment ambient temperature could be significantly increased due to the results of the LOCA. The conditions at this time result in an indicated level error due to the elevated temperature of the instrument reference leg, and additionally, an error is also introduced due to the change in the variable leg temperature.
In this case, the two errers impressed on the level transmitter are additive leading to a total indicated level error greater than if only the effects on the reference leg trere considered.
Since identification of these problems, Maine Yankee has developed a series of correction curves for the steam generator and pressurizer level instruments which allow the operators to make corrections to the indicated level which take into account temperature (density) changes for both the reference and variable legs.
Incorporation of these curves into applicable emergency procedures and the training of operators in their application and use is. presently underway. This effort is expected to be completed by September 1, 1980.
We trust this information is satisfactory.
Should any further information be required, please feel free to contact us.
Very'truly yours, MAINE YANKEE ATOMIC POWER COMPANY D u/
D. E Moody Manager of Operations EWJ/sec
.- -.