ML20082B343
| ML20082B343 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 11/15/1983 |
| From: | Schroeder C COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.E.4.2, TASK-TM 7620N, IEB-80-06, IEB-80-6, NUDOCS 8311210144 | |
| Download: ML20082B343 (5) | |
Text
v[h Commonwealth Edison C
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/ one First N;tional Ptsza. Chic go, lihnois v ' Addrzss R; ply to: Post Office Box 767
\\N Chicago. Illinois 60690 November 15, 1983 Mr. Harold R. Denton, Director Of fice of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
LaSalle County Station Units 1 and 2 Valve Repositioning Upon Reset of Containment Isolation (IE Bulletin 80-06)
NRC Docket Nos. 50-373/374 Reference (a):
Commission Request for Additional Information t
Dear Mr. Denton:
Reference request asked for specific justification for modifying the logic on certain valves that could be repositioned upon reset of the containment isolation logic.
Region III Staff had suggested that these valves should have been included within the coverage of Item 11.E.4.2 of NUREG-0737.
The response to the Commission's request is provided in the Attachment.
The operations of the valves were reviewed in both the containment isolation dependability review as documented in the FSAR Section L.29 and in the IE Bulletin 80-06 review of ESF system jeopardy following reset of an ESF actuation signal as documented in the response to FSAR question Q31.285.
The conclusion is that these valves do not need modifications to their control circuits to assure containment isolation.
To the best of my knowledge and belief the statements contained herein and in the Attachment are true and correct.
In some respects these statements are not based on my personal knowledge but upon information furnished by other Commonwealth Edison employees.
Such information has been reviewed in accordance J
with Company practice and I believe it to be reliable.
If there are any further questions on this matter, please contact this of fice.
Very truly yours, bYo$oo b
/
~
C. W. Schroeder cc:
NRC Resident Inspector - LSCS k
Attachment 7620N l
1
\\
L
e ATTACHMENT There are two issues of concern regarding the reset of actuation signals and their effect on certain valves recently pointed out by Nuclear Regulatory Commission (NRC) inspectors at LaSalle County Station.
The first of these is the issue of containment isolation dependability.
This issue was brought to light with the issuance of NUREG-0578, Section 2.1.4, and later modified by NUREG-0737, Item II.E.4.2.
These NUREG's required that the following criteria be considered in the circuit controls for containment isolation valves:
A.
There should be diversity in the parameters sensed for the initiation of containment isolation.
B.
Systems with containment isolation valves should be classified as essential or nonessential, and the isolation designs modified accordingly.
C.
All nonessential systems shall have automatic isolation by the containment isolation signal.
D.
The design circuit for the automatic containment isolation valves shall be such that resetting the isolation signal will not result in the automatic reopening of the containment isolation valves, and that reopening of the containment isolation valve shall require deliberate operator action.
E.
The containment setpoint pressure which initiates containment isolation for the essential penetrations should be reduced to the minimum, compatible with normal operating conditions.
F.
Containment purge valves should conform to branch technical position CSB 6-4.
G.
Containment vent and purge isolation valves must close on a high radiation signal.
These are the initial seven criteria from NUREG 0737, for which the FSAR Appendix L response was made.
As a result of the issuance of these requirements, the LaSalle County Station containment isolation design was reviewed to determine whether any circuit modifications were necessary to comply.
with these requirements.
In this review, each containment.
penetration, and the function of each pipeline through lt, was reviewed to determine whether the line served.an essential function, and if not, whether there were properly applied containment isolation signals.
_ _ _ :_ L_ _ ____ - _- _ _
b
. The second issue to be considered is the safety significance of the reset of an ESF actuation signal.
An ESF actuation signal is that signal which initiates the performance of an ESF system such as the startup of the high pressure core supply system, the initiation of standby gas treatment, or the actuation of the control room Heating Ventilating and Air Conditioning (HVAC) emergency filter train.
This issue came about through the issuance of IE Bulletin 80-06 in which design deficiencies were discovered during a review of safety injection systems at the North Anna Nuclear Power Station - Unit 1.
When this issue was brought to light on LaSalle County Station licensing, an additional review was performed of all the ESF systems at LaSalle County Station to determine if any ESF systems were being jeopardized through the automatic reset of an ESF actuation signal.
This review resulted in a modification of several ESF system circuits, including valves and/or dampers in the control room HVAC system, the auxiliary electrical equipment room HVAC system, the containment monitoring system, the standby gas treatment system, the reactor building ventilation system, reactor fluid sample lines, and drywell sump isolation lines.
Recently, Edison was requested by Region III inspectors to investigate the reasons why the following valves were determined to not require any circuit modifications as a result of IE Bulletin 80-06:
E21-F333 E12-F099A E22-F354 E12-F099B E51-F354 E51-F008 E51-F355 E51-F063 s
At LaSalle County Station, there are certain signals whose function is solely to isolate the containment and other signals whose function is solely to actuate ESF systems such as core cooling injection, standby gas treatment, or control room HVAC initiation.
None of the valves listed above receive signals which are classified as ESF actuation signals.
Therefore, they were determined to not require circuit modifications per the IE Bulletin.
The following valves are used as paths to allow the equalization of pressure across a testable check valve on the injection lines of ESF Emergency Core Cooling Systems (ECCS):
E21-F333 E51-F354 E22-F354 E51-F355 The normally-closed valves function only when an operator manually initiates them from a control room to equalize the pressure across the check valve before actuating the check valve.
The amcunt
~
. of time that these valves are open is extremely short.
In addition, when this test is performed, the injection valve, immediately upstream of the check valve, must be in a closed position, thereby insuring reactor coolant pressure boundary integrity (these equalization valves are 3/4 of an inch in size and are equipped with limit switches to indicate to the operator the valve position at all times).
Even though the time of use of these valves is very short, and infrequent, the LaSalle County Station design has included the use of a containment isolation signal to prevent these valves from opening in the event of a Loss-Of-Coolant Acr.ident (LOCA), and to close the valve should there be a LOCA present at the time of testing the check valve.
Based on the functional definition described above for these valves, they were not classified under the IE Bulletin 80-06 criteria as receiving an ESF actuation signal.
These valves do not perform ESF system functions.
The next logical question which was addressed for these valves was "should these valves have been included in the list of containment isolation valves which require modification as a result of NUREG-0737?"
The answer to this is, "these valves were considered amongst all of the valves requiring modificat' ion, and judged that modification is not required."
Per NUREG-0737, all systems penetrating the primary containment and/or reactor coolant pressure boundary, were classified as being either essential or nonessential.
In that classification, it was determined that all of the equalizing valves (although not essential themselves) were connected to systems which were classified as essential, and that isolation of the safety injection lines to which these valves were attached would be detrimental to the recovery from a LOCA.
Safety injection can occur following containment isolation and, therefore, any lines which could be required to function to achieve safety injection should not be isolated.
As stated above, these valves do not receive ESF actuation signals.
Further, they are normally closed and are opened infrequently and only for short periods.
When they are open for testing, the injection valve upstream of them is closed.
If a containment isolation is necessary, these valves would remain t
closed.
If they happened to be in the open position when receiving a containment isolation signal, they would close.
Finally, if they had been in the open position and the containment isolation signal were reset, and the core coollng injection valve was still open (due to the requirement for core cooling), there would be flow in the line toward the reactor, and the position of the bypass line valve is immaterial.
When the injection system is no longer required, the injection valve would be closed, thus assuring containment 4
isolation.
Therefore, it is concluded a modification to these valve circuits is not necessary.
L
l 1 Evaluation was also made for E51-F008 and E51-F063.
These valves are used only to isolate the Rector Core Isolation Cooling (RCIC) steam line in the event of excess leakage to the RCIC steam tunnel or equipment cubicle.
These valves do not receive ESF actuation signals and, therefore, were not included in the IE Bulletin 80-06 study.
Similarly, these valves do not receive containment isolation signals but only area leak detection signals.
It was determined that because the RCIC system is depended upon to recover from a LOCA, for long-term inventory control, the RCIC steam supply line is classified as an essential system line, and should not be needlessly isolated in the event of a LOCA.
The function of the RCIC system should not be jeopardized due to a containment isolation event.
Therefore, it was determined that no circuit modification should be made to these valves.
Each valve has a separate reset button which must be pressed to allow these valves to open.
The Station procedure for resetting these valves raquires that the valves be closed prior to resetting the logic.
Examination was also made of the operation of valves E12-F099A and E12-F0998.
The function of these normally-closed valies is to allow the pre-warming of the shutdown cooling line pri)r to taking the reactor vessel to cold shutdown condition.
There valves similarly do not receive ESF actuation signals and, therefore, were not modified per the IE Bulletin.
They were provided with containment isolation signals, however.
Again, the operaticn of these valves is limited to a short time period, and additionally, only when the reactor pressure is below the set pressure which allows the shutdown cooling mode to take place.
If a cuntainment isolation were necessary, these valves would remain closed.
If the valves were open prior to receipt of the isolation signal, the valves would close.
Additionally, in the event of a containment isolation signal reset, the E12-F053A and E12-F0538 valves, which are upstream of the E12-F099A and E12-F0998 valves, and which are containment isolation valves, will not reset to their i
j' open position.
Therefore, it was determined that modifications to these valve circuits were not necessary.
l Finally, as a matter of consistency in the ~ record, Appendix L of the FSAR will be revised to include the outboard feedwater check valves 821-F032A,B which previously were evaluated as l
indicated in the response to NRC question Q31.285.
For these valves, the ESF isolation signal only seats the valve; once seated, l
the ESF signal is no longer needed and movement of the operator upon reset has no effect.
l The above isolation.valven have been reviewed by the.
l on-site safety review group who have independently concluded that l
justification exists for not modifying.the. control circuitry.
l l