ML17263A496
| ML17263A496 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 12/02/1993 |
| From: | Ruland W, Scholl L NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | |
| Shared Package | |
| ML17263A494 | List: |
| References | |
| 50-244-93-21, NUDOCS 9312170013 | |
| Download: ML17263A496 (11) | |
See also: IR 05000244/1993021
Text
0
U.S. NUCLEAR REGULATORY COMMISSION
REGION I
REPORT/DOCKET NOS.
50-244/93-21
LICENSE NO.
LICENSEE:
FACILITY:
Rochester
Gas and Electric (RG&E) Corporation
89 East Avenue
Rochester,
New York 14649
Robert E. Ginna Nuclear Power Plant
INSPECTION AT:
Corporate Office
INSPECTION DATES:
October 4-13, 1993
INSPECTOR:
Larry Scho, Reactor Engineer
Electrical Section, EB, DRS
rr x.rap
Date
APPROVEDBY'm
H. Ruland
Chief
ectrical Sectio, EB, DRS
r>- >- +>
Date
9312170013
931210
ADOCK 05000244
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g NRC
distribution system functional inspections (EDSFIs) at various facilities.
One unresolved
item, regarding the lack of a comprehensive coordination analysis for circuit breakers,
was
also reviewed.
~Reset:
The issues inspected were found to have been adequately reviewed and addressed
by RG&E with the exception of the emergency electrical bus logic testing.
The surveillance
testing was deficient in that load shedding of the emergency buses was not performed as
required by the plant technical specifications.
This deficiency was of particular concern
since problems with the testing of emergency diesel generators
have been the subject of
recent NRC Information Notices and as such afforded RG&E the opportunity to discover the
surveillance test deficiencies.
N
The inspector found that RG&E performed a comprehensive coordination analyses for 480V
and 4160V circuit breakers and the associated
unresolved item was closed.
DETAILS
1.0
BACKGROUND
In 1991, the NRC performed a safety system functional inspection on the electrical
distribution system at R. E. Ginna Nuclear Power Station.
Since 1989 the NRC has
performed more than 50 electrical distribution system functional inspections (EDSFIs) at
licensed reactor facilities throughout the country.
Information regarding significant
deficiencies identified during these inspections has been provided to all reactor plant licensees
through the issuance of NRC Information Notices.
The inspector reviewed several of these
deficiencies for applicability to the Ginna plant and to determine ifRG&E had taken the
appropriate actions in response
to the information.
One previously unresolved item involving
the lack of a comprehensive circuit breaker coordination analysis for circuit breakers was
also reviewed.
2.0
INSPECTION DETAILS
The inspector held discussions with various members of the licensee's staff and reviewed
drawings, calculations and procedures
associated
with the areas inspected.
The issues that
were reviewed are discussed in the following NRC Information Notices:
~
91-13
Inadequate Testing of Emergency Diesel Generators
(EDGs)
~
91-29 and
Supplement
1
Deficiencies Identified During Electrical Distribution
System Functional Inspections
~
91-51
~
92-40
Inadequate Fuse Control Program
Inadequate Testing of Emergency Bus Undervoltage Logic
Circuitry
~
92-53
Potential Failure of Emergency Diesel Generators Due To
Excessive Rate of Loading
2.1
Molded Case Circuit Breaker Testing (IN 91-29)
The NRC has identified deficiencies in licensee programs to test circuit breakers.
These
deficiencies included inadequate procedures,
inadequate test acceptance
criteria, inadequate
test equipment and inadequate control of testing.
Ginna Station Procedure M-1005, "Electrical Preventive Maintenance of Buses, Motor
Control Centers, Transformers and Breakers," specifies the test frequency of electrical
components.
The inspector reviewed this procedure and confirmed that molded case circuit
breakers were included within the scope of the preventive maintenance program.
The
procedure specifies that testing or replacement of circuit breakers willbe performed on a
sampling basis and specifies the frequency of testing for the various breakers.
The safety-
related breakers are tested at least once every 60 months and the frequency of may be
adjusted based on test results in accordance with the Reliability Centered Maintenance
program.
The detailed testing instructions are specified in Procedure MP-056.01, "AC
Motor Control Center Maintenance and Subcomponent Replacement."
The inspector concluded that RG&E has adequately defined the maintenance
and testing
requirements for molded case circuit breakers and has developed the necessary
test
procedure.
2.2
Interrupting Capacity and Coordination of Fault Protection Devices gN 91-29)
NRC inspections have identified conditions in which the interrupting capacities of fault
protection devices were not adequate for the application and other cases in which a lack of
coordination could have resulted in a branch circuit fault causing the trip of a feeder circuit
breaker or fuse.
During the EDSFI at the Ginna Station, the inspection team identified a concern that the
margin between some of the Class 1E full load currents and the lower band of the breaker
overcurrent trip set point was very narrow.
This could result in breaker trips when operating
under degraded voltage conditions.
At that time RG&E provided some preliminary
calculations that indicated there was'no cause for concern.
The team was also informed that
a comprehensive
coordination analysis was in progress to document the basis for all of the
set points for the 480V and 4160V breakers.
The inspector reviewed Design Analysis DA-EE-93-107-07, "4160 Volt Overcurrent Relay
Coordination and Circuit Protection Study," and DA-EE-93-104-07, "480 Volt DB Breaker
with Amptector Retrofit Coordination and Circuit Protection Study," that document the
completed breaker coordination analysis.
These documents contain recommended
set point
changes,
intended to optimize the protection of loads and circuit coordination, and the basis
for the new set points.
The calculations and associated
set point changes take into account
operation at degraded voltage conditions.
BG&E plans to implement the set point changes
during the next refueling outage.
Based on these actions unresolved item 50-244/91-80-06 is
closed.
2.3
Emergency Diesel Generator Mechanical Interfaces gN 91-29 Supplement 1)
The NRC found deficiencies involving EDG mechanical systems interfaces such as air start
systems,
fuel oil storage and heating, ventilation and cooling systems.
To verify the adequacy of the EDG air start system RG&E performed test MET-051, "Test
Specification for the Diesel Generator Air Start System."
The inspector reviewed the results
of this test that demonstrated
that the diesel would start at least five times from the nominal
air receiver pressure,
including one start from an air pressure that was below the air receiver
low pressure alarm point.
0
4
At the D. C. Cook site, it was discovered that the ability of the EDG ventilation system and
engine air intake ducting to withstand the differential pressure effects of a tornado may not
have been considered during the initial design of these components.
During the Ginna Station Structural Upgrade Program, in response to the Systematic
Evaluation Program, RG&E performed a calculation (Engineering Work Request 3296) to
determine what vent area would be required for the various structures to minimize the
differential pressure effects of a tornado.
For the diesel generator building the results of the
calculation indicated that the necessary vent area required would be 4.8 square feet.
The
existing vent area is 72 square feet.
Based on this information RG&E concluded that there
was reasonable
assurance
that tornado effects on the emergency diesel generator building
ventilation would be negligible.
2.4
Fuse Control Program (IN 91-51)
Numerous problems associated with the control of fuses in the plant electrical systems have
been identified during NRC inspections and by licensees
as reported in Licensee Event
Reports.
Fuse control deficiencies include:
inadequate root cause evaluation of blown fuses
inadequate verification of design information for installed and replacement
fuses
inadequate identification and labeling of fuses
improper coordination of fuses and circuit breakers
personnel errors
The inspector reviewed Plant Procedure M-106, "Replacement or Inspection of D.C. Fuses,"
and found that it contained detailed directions for the control of DC fuses.
The fuse data
base was developed under EWR 3341 that also performed a coordination study for the DC
fuses.
The use of M-106 and the associated
schematic drawings willensure the replacement
fuse is of the correct voltage, current and interrupting capacity rating.
The preventive
maintenance (PM) analyst is required to review the completed M-106 procedures
to ensure
that adverse trends are detected.
~
'rocedure
A-25.1, "Ginna Station Event Report," requires the duty engineer to evaluate if
the root cause has been determined and ifit has not it is referred to the PM Analyst for
further evaluation.
This procedure should ensure that the root cause of a blown fuse is
investigated.
The inspector concluded that a good dc fuse control program was in place and noted that a
similar-program for the control of ac fuses was being developed.
6
2.5
Emergency Bus Undervoltage Logic Circuitry Testing (IN 92-40)
During the EDSFI inspection at the LaSalle County Nuclear Station, the NRC found that the
surveillance test used for the loss of offsite power test was not testing the capability of the
undervoltage logic circuitry to de-energize the emergency bus.
The loss of offsite power was
simulated by tripping the emergency bus feeder breakers.
One function of the undervoltage
logic circuitry is to open the feeder automatically during an undervoltage condition to ensure
that the emergency diesel generator is not connected to a degraded offsite power source.
Manually tripping the feeder breaker to initiate the test did not permit the testing of this
function.
NRC Information Notice 91-13, "Inadequate Testing of Emergency Diesel Generators,"
discusses
problems associated
with EDG testing, including the failure to perform adequate
diesel generator load tests and emergency bus load shed tests.
The RG&E evaluation of Information Notice 92-40 indicated that Surveillance Procedure
RSSP 2.2, "Diesel Generator Load and Safeguard Sequence Test," performed a test of the
capability of the undervoltage relays to trip the emergency bus feeder breakers.
The
inspector reviewed this procedure along with the emergency diesel generator startup logic as
described in Figure 8.3-5 of the R.E. Ginna Updated Final Safety Analysis Report (UFSAR).
There are four emergency
buses at the Ginna plant, two associated
with the A train (buses
14
and 18) and two associated
with the B train (buses
16 and 17).
The trip logic for the
emergency bus feeder breakers is such that the breakers willtrip as the result of the existence
of one of two following conditions:
1)
Direct trip on an undervoltage condition on the emergency bus, or
2)
An undervoltage condition on the other emergency bus in the same train, coincident
with a safety injection (Sl) signal.
The inspector found that the testing of the B train emergency buses, in accordance with
Procedure RSSP 2.2, initiated a trip of the feeder breaker for emergency bus 17 by inserting
an undervoltage signal in the logic for bus 16 and then initiating a SI signal (condition 2
above).
The trip of the feeder breaker for bus 17 de-energizes
the bus, thereby initiating the
undervoltage logic for bus 17.
The bus 17 undervoltage condition, coincident with the SI
signal then trips the bus 16 feeder breaker (condition 2 above).
This test method does not
test the direct trip of the feeder breakers due to an undervoltage signal (condition
1 above).
The inspector asked the licensee ifother tests existed that would test the undervoltage trips of
the feeder breakers.
RG&E identified Procedure PR-21.1, "Protective Relay Trip Test-
480V Undervoltage for Buses
14 or 16."
The inspector reviewed this procedure and
verified that it performed trip tests of the bus 14 and bus 16 feeder breakers;
however, it was
also found that a similar procedure for buses
17 and 18 did not exist.
n
As a result of this discrepancy,
and after reviewing additional surveillance tests, the inspector
then requested
to review the procedures
that performed the testing of the load shedding
depicted on the UFSAR logic diagram and required by plant technical specification (TS) 4.6.1.e.3.a.
RG&E performed a review of the existing surveillance procedures
and on
October 11, 1993, concluded that procedures
were not in place to perform the load shed
testing for the safeguards
loads on the emergency buses.
The emergency diesel generators
were then declared inoperable until additional testing was performed on October 13, 1993.
The results of this testing verified that the undervoltage trip of the bus 17 and 18 feeder
breakers and the load shedding circuits functioned properly.
The inspector concluded that the plant procedures did not adequately
test the bus
undervoltage logic and the failure to perform the load shed testing is a violation of
TS 4.6.1.e.3.a (50-244/93-21-01).
2.6
Emergency Diesel Generator Rate of Loading gN 92-53)
The NRC found at the Calvert Cliffs Nuclear Power Plant that under certain conditions loads
could be sequenced
onto the emergency bus more rapidly than the design capability of the
RG&E has 'developed an emergency diesel generator dynamic load analysis to assess
the
capabilities of the emergency diesel generators
to start and accelerate
the safety loads during
an accident.
These analyses; DA-EE-92-111-01, "Diesel Generator A Dynamic Loading
Analysis," and DA-EE-112-01, "Diesel Generator B Dynamic Loading Analysis," were
reviewed in their draft form during the EDSFI inspection and since have been finalized.
The
inspector noted that the dynamic load analysis computer model is being used to assess
the
effects of various factors on the EDG operation, including items such a time delay relay set
point drift.
The inspector found the development of this computer model to be a good initiative on the
part of RG&E and noted that the engineering staff continues to employ it as a tool to resolve
operational questions with the EDGs.
3.0
CONCLUSIONS
The inspector concluded that, with the exception of the testing of the emergency bus
undervoltage logic, BG&E was adequately evaluating and implementing corrective actions
based on industry findings related to the electrical distribution system.
Actions necessary
to
resolve issues identified by the EDSFI inspection team have been completed in a timely
manner.
At the conclusion of the inspection on October 8, 1993, the inspector met with licensee
representatives
listed in Attachment 1.
The inspector summarized the scope and results of
the inspection at that time.
Followup discussions
were conducted on October 12 and
13, 1993, with Mr. Wrobel and Mr. Millerto review the results of your additional testing of
the EDG logic circuitry.
The licensee acknowledged
the inspection findings as detailed in this report and had no
additional comments regarding the inspection results.
ATTACHM<22IT1
Persons Contacted
h
r
El
ri
i n
C. Forkell, Electrical Engineering Manager
T. Miller, Lead Electrical Engineer
J. Sargent, Electrical Engineer
L. Sucheski, Structural Engineering Manager
G. Wrobel, Licensing Manager
C. Vitali, Lead Mechanical Engineer
Indicates those who attended the exit meeting on October 8, 1993.