ML17174A805
| ML17174A805 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Quad Cities, LaSalle  |
| Issue date: | 07/19/1991 |
| From: | Miller H NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Reed C COMMONWEALTH EDISON CO. |
| Shared Package | |
| ML17174A806 | List: |
| References | |
| GL-89-10, NUDOCS 9107240137 | |
| Download: ML17174A805 (3) | |
See also: IR 05000237/1991011
Text
Docket No. 50-237
Docket No. 50-249
JUL l 9 1991
Commonwealth Edison Company
ATTN:
Mr. Cordell Reed
Senior Vice President
Licensing Department-Suite 300
Opus West III
1400 Opus Place
Downers Grove, IL
60515
Dear Mr. Reed: *
SUBJECT:
DETERMINATION IF BRANCH TECHNICAL POSITION (BTP)
SPLB* (ASB) 3-1 IS APPLICABLE FOR SIZING MOTOR-OPE~TED
VALVES FOR GENERIC LETTER 89~10
During a recent inspection of the program implemented by
Commonwealth Edison Company's (CECo) Dresden Station to address
Generic Letter (GL) 89-10, "Safety Related Motor-operated Valve
(MOV) Testing and Surveillance," Region III *inspectors identi.fied
a concern with respect to the worst-case differential pressure
(dp) for which a MOV is to operate against (Open Item
50-237/91011-01; 50-249/91010-01).
In GL 89-10, the NRC staff requested licensees to review and
document the design basis for the operation of each MOV within
the scope o( the generic letter program .. The .purpose of the
design basis review is to determine the worst case dp and pther
conditions for both normal operations and abnormal conditions
where MOVs are required to operate.
Following the determination
- of the maximum (or worst case) dp, a review is conducted to
select and set the MOV switches and to ensure that the MOV is
capable of operating under worst-case conditions.
Since GL 89-10 requests licensees to review the design basis to
determine the worst case dp and then size MOVs to ensure their
operability, this process should be completed for MOVs used to
isolate a high energy line break (HELB).
These MOVs normally
consist of valves in High Pressure Coolant Injection (HPCI),
Reactor Core Isolation Cooling (RCIC), Isolation.condenser steam
supply lines, and Reactor Water Cleanup (RWCU) lines, whose
function is to isolate during a pipe break.
Performing a design basis review for HELB MOVs as requested by GL 89-10 would lead a licensee to determine the pressure at which a
pipe break would occur and to subsequently size the MOV to ensure
9107240137 910719
ADOCK 05000237
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Commonwealth Edison Company
2
JUL 1.9 '191
its capability to operate against the assumed pressure.
The
pressure for which a HELB is assumed to occur then becomes
critical for ensuring an MOV is sized properly.* If a lower
pressure is assumed than the point at which a pipe break actually
occurred, an MOV may not have been adequately sized for closure.
During the inspection at Dresden Station, Region III inspectors
noted that CECo used BTP SPLB (ASB) 3-1 to obtain guidance for
determining the pressure that could be assumed for calculating
the worst case dp that would be seen by an MOV during a high
energy line break.
The NRC staff has reviewed CECo's reliance on BTP SPLB (ASB) 3-1
in assuming nominal reactor pressure for design-basis reviews of
BTP ASB 3~1 was intended to
address the protection of plant equipment from the dynamic
effects of pipe breaks and harsh environments resulting from pipe
breaks.
This BTP was not.written for developing MOV design
bases, and the assumptions used for the development of this BTP
are not applicable for GL 89-10.* Through GL 89-10, the NRC staff
is requesting licensees to verify tnat .MOVs within the scope of
the generic letter are capable of performing their intended
functions under worst case dp and other conditions.
Assuming
nominal reactor pressure will not demonstrate that the MOVs in
question are capable of isolating a break initiated at maximum
reactor pressure.
Qualifying MOVs to operate under nominal
rather than maximum dp and flow conditions will limit the
scenarios for which the MOVs are required to operate to only
certain events and reduces the options available to plant
operators during abnormal plant conditions.
Therefore, NRC does not consider the use of nominal reactor
pressure* in design-basis reviews for HELB MOVs to be consistent
with the CECo commitments regarding GL 89-10.
CECo should assume
maximum reactor pressure in its determination of the worst case
dp for an MOV in a pipe directly connected with the reactor
vessei.
With the maximum reactor pressure (i.e., lowe~t relief
valve setpoint pressure) as a starting point, the dp across the
valve should be calculated by considering factors such as losses
in the piping.
Commonwealth Edison Company
3
Should you have any questions concerning this letter, please*
contact Mr. Marc Huber of my staff at FTS 388-5789.
Sincerely,
ORt.GINAL SIGNED BY HUBERT J. MILLER
H. J. Miller, Director
Division of Reactor Safety
cc:
D. Galle, Vice President,
BWR Operations
T. Kovach, Nuc.lear Licensing
Mariager
E. D. Eenigenburg, station
Manager
DCD/DCB (RIDS)
OC/LFDCB
J. Zwolinski, NRR
B. Siegel, NRR
~. *
T. Scarbrough, NRR
v.6
Resident Inspectors-Dresden,
LaSalle, Quad Cities
Richard Hubbard
J. w. Mccaffrey, Chief
Public Utilities Division
Robert Newmann, Office o.f Public
Counsel, State of Illinois
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