United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 84-38: Problems with Design, Maintenance, and Operation of Offsite Power Systems

                                                            INS No. 6835 
                                                            IN 84-38 

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF INSPECTION AND ENFORCEMENT
                            WASHINGTON, DC 20555 

                                May 17, 1984

Information Notice No. 84-38:   PROBLEMS WITH DESIGN, MAINTENANCE, AND 
                                   OPERATION OF OFFSITE POWER SYSTEMS 

Addressees: 

All power reactor facilities holding an operating license (OL) or 
construction permit (CP). 

Purpose: 

This information notice is provided as a notification of potentially 
significant problems pertaining to the design, maintenance, and operation of 
offsite power systems. It is expected that recipients will review their 
facilities and consider actions, if appropriate, to preclude similar 
problems occurring at their facilities. However, suggestions contained in 
this information notice do not constitute NRC requirements and, therefore, 
no specific action or written response is required. 

Description of Circumstances: 

Turkey Point Nuclear Units 3 and 4 recently experienced a series of events 
that included reactor trips, unscheduled shutdowns, and loss of offsite 
power to Unit 3. These events occurred as a direct result of problems with 
the design, maintenance, and operation of the offsite power systems. 

The first event occurred on February 12, 1984, when an improperly calibrated
relay for the startup transformer of oil fired Units 1 and 2 sensed a 
current differential and isolated the portion of the switchyard bus feeding 
the single Unit 3 startup transformer and a new 3C auxiliary transformer for 
that unit. The Unit 3 reactor tripped on loss of an electrically driven main 
feedwater pump powered from the 3C auxiliary transformer and bus. With the 
start-up transformer also lost, emergency diesel generators were required to 
provide power to the vital buses and the unit was stabilized on natural 
circulation. Later that day, while attempting to restore offsite power to 
Unit 3 from the Unit 4 new 4C auxiliary transformer, a switching error 
resulted in reactor trip of Unit 4. There were no written procedures for 
realignment of offsite power systems following the loss of offsite power to 
one of the units (Unit 3 in this case). 

Another event occurred on February 16, 1984, when the Unit 4 reactor tripped
and Unit 3 experienced loss of offsite power. This event was initiated by a 
relay in the recently installed offsite power cross-tie feeder switchgear 
that included buses 3C and 4C. This relay was mounted on a metal-clad 
switch-gear door that was improperly installed, which caused it to bind. The 
vibrations 


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                                                            IN 84-38 
                                                            May 17, 1984 
                                                            Page 2 of 2 

from forcing the door open or closed actuated the relay. This resulted in a 
Unit 4 trip from loss of power to the 4C bus which supplied one electrically
driven main feedwater pump. Seconds later, jarring of a similarly mounted 
relay caused isolation of the switchyard quadrant feeding Unit 3 and result-
ant loss of power to the 3C bus, loss of one electrically driven main feed-
water pump, reactor trip, and loss of power to the Unit 3 startup transform-
er. 

Following these events, the licensee informed the NRC that the new 3C and 4C
auxiliary transformers and associated equipment were added with the 
objective of enhancing the availability of offsite power,systems. The design 
changes for these additions were classified as non-safety-related but were 
covered in the quality assurance program. However, they were not reviewed 
with respect to the requirements of 10 CFR 50.59 by the plant nuclear safety 
committee. 

As a followup to these events, the licensee instituted short- and long-term 
corrective action programs to review the overall design of offsite power 
systems and to strengthen the procedures and administrative controls. As a 
part of the short-term program, functional testing of 4-kV breakers for non-
safety-related buses was performed; this test revealed loose bolts, 
misaligned and dirty contacts, worn parts, and the mechanical failure of one 
breaker to trip. The short-term corrective actions program was completed 
before unit startup. 

A partial listing of other similar loss-of-offsite-power events is provided 
in Attachment 1 to this notice. 

The general concern is that design, maintenance, and operational problems in
electrical equipment considered to be non-safety related can greatly degrade
access to offsite power sources. This is not consistent with the General De-
sign Criteria objectives. The concern is particularly valid where station 
service loads are arranged, as at Turkey Point Units 3 and 4, such that a 
single electrical fault can cause a transient resulting in a plant trip and 
also defeat immediate access to offsite power sources. The concern is also 
particularly valid for facilities with multiunit plants or a common switch-
yard for nuclear and non-nuclear units. 

If you have any questions regarding this matter, please contact the Regional
Administrator of the appropriate NRC regional office or this office. 



                                   Edward L. Jordan, Director 
                                   Division of Emergency Preparedness 
                                      and Engineering Response 
                                   Office of Inspection and Enforcement 

Attachments: 
1.   Partial List of Recent Loss of Offsite Power Events 
2.   List of Recently Issued IE Information Notices 

Technical Contact:  R. Singh, IE 
                    (301) 492-8068

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                                                            Attachment 1 
                                                            IN 84-38 
                                                            May 17, 1984 

           PARTIAL LIST OF RECENT LOSS-OF-OFFSITE-POWER EVENTS 

Plant/Date                    Event Summary 

1.   LaSalle 1,               Partial loss of offsite power caused by a 
     10/26/83                 procedural error and personnel oversight when 
                              securing a Unit 2 transformer. 

2.   Summer 1,                Internal fault at Parr Steam Plant (a 
     9/11/83                  non-nuclear unit) caused loss of offsite 
                              power. 

3.   Brunswick 1,             Personnel error caused loss of offsite power 
     4/26/83                  when a 230 kV bus was inadvertently tripped. 

4.   Quad Cities 2,           Preferred power was being taken out of service
     6/22/82                  for maintenance, and a personnel error caused 
                              a reactor trip resulting in complete loss of 
                              offsite power. Twenty-two minutes into the 
                              event, one of the emergency diesel generators 
                              tripped as a result of underexcitation. 

5.   Prairie Island 1,        During an attempted start of a cooling tower 
     7/8/81                   pump, an improperly set undervoltage 
                              protection relay caused a partial loss of 
                              offsite power. 

6.   Salem 1 and 2,           Partial loss of offsite power to both units 
     5/21/81                  resulting from a design deficiency in the, gas
                              turbine Unit 3. 

7.   Monticello,              A bus fault was caused by operator error. A 
     4/27/81                  design error caused the undervoltage relays to
                              trip all offsite power sources instead of    
                              isolating only the faulted bus. 

8.   LaCrosse,                Loss of offsite power caused by an operator 
     2/1/81                   opening a wrong breaker. 

9.   Beaver Valley 1,         Loss of 138 kV bus resulted in partial loss of
     2/1/81                   offsite power. During the event, the auto load
                              sequencer of one of the emergency diesel 
                              generators failed as a result of improper 
                              wiring  (design error) and a disconnected 
                              timer relay. 

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