Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
ACCESSION #: 9605070110
ABB
April 15, 1996
LD-96-009
Document Control Desk
U.S. Nuclear Regulatory Commission
Washington, D.C, 20555
Subject: Report of a Deviating Condition in a Reactor Trip Function
Dear Sir:
Combustion Engineering, Inc. (ABB-CE) hereby notifies the Nuclear
Regulatory Commission of a condition or circumstance involving a reactor
protection system trip function which has the potential to contribute to
the exceeding of a safety limit. The deviating condition evaluated
involves nuclear instrumentation decalibration factors, which may not
have been adequately compensated for fully when originally setting the
trip setpoint, and which, therefore, have the potential to adversely
affect the High Logarithmic Power channel trip function. The
uncompensated decalibration factors are Potentially nonconservative in
nature and could, therefore, cause a trip, if needed, to occur at a power
level higher than that accounted for in safety analyses.
Evaluations were performed by ABB-CE to determine if this situation would
in fact result in exceeding any safety limits, Based on the result of
these evaluations ABB-CE has concluded that because of the discretionary
conservatism built into the input parameters for the one affected safety
analysis, that the original High Logarithmic Power trip setpoint remains
acceptable without creating the potential to exceed a safety limit- ABB-
CE has chosen to report this condition because the situation could
conceivably be applicable to other NSSS vendor designs utilizing a
reactor protection system trip for subcritical events based upon absolute
power if nuclear instrumentation decalibration factors are not accounted
for appropriately. The Enclosure provided herewith summarizes the
information available to ABB-CE regarding the subject condition.
ABB Combustion Engineering Nuclear Power
Combustion Engineering. P.O. Box 500 Telephone (860) 688-1911
Inc. 2000 Day Hill Rd. Fax (860) 285-5202
Windsor, CT 06095-0500
Document Control Desk LD-96-009
April 15, 1996 Page 2
[f you have any questions, please feel free to contact me or Mr. Chuck
Molnar of my staff at (203) 285-5205.
Very truly yours,
COMBUSTION ENGINEERING, INC
J. C. Rickard, Director
Operations Licensing
Enclosure: As stated
cc: R. S. Siudek (ABB-CE)
ENCLOSURE
ABB Combustion Engineering Nuclear Operations
Report of a Deviating Condition in a Reactor Trip Function
April 15, 1996
ABB Combustion Engineering Nuclear Operations
Report of a Deviating Condition in a Reactor Trip Function
(i) Name and address of the individuals informing the Commission:
I. C. Rickard, Director
Operations Licensing
Combustion Engineering, Inc.
2000 Day Hill Road
Windsor, CT 06095-0500
(ii) Identification of the facility, the activity, or the basic
component supplied or such facility or such activity within the
United States which fails to comply or contains a defect:
The condition being reported was initially identified at the
Waterford Steam Electric Station Unit No. 3 (WSES-3).
Specifically, the deviating condition involves nuclear
instrumentation decalibration factors, which may not have been
adequately compensated for fully when originally setting the
trip setpoint. These decalibration factors are related to the
reactor High Logarithmic Power channel trip function and are
potentially nonconservative In nature.
(iii) Identification of the firm constructing the facility or
supplying the basic component which fails to comply or contains
a defect:
Combustion Engineering, Inc.
2000 Day Hill Road
Windsor, CT 06095-0500
(iv) Nature of the defect or failure to comply and the safety hazard
which is created or could be created by such defect or failure
to comply.,
Although the High Logarithmic Power trip function is only
credited at low power levels (from
