United States Nuclear Regulatory Commission - Protecting People and the Environment



CR77016 

                               UNITED STATES 
                       NUCLEAR REGULATORY COMMISSION 
                          WASHINGTON, D. C. 20555 

                             December 9, 1977 

MEMORANDUM FOR:     B. H. Grier, Director, Region I 
                    J. P. O'Reilly, Director, Region II 
                    J. G. Keppler, Director, Region III 
                    E. M. Howard, Director, Region IV 
                    R. H. Engelken, Director, Region V 

FROM:               H. D. Thornburg, Director, Division of Reactor 
                         Operations Inspection, IE 

SUBJECT: IE CIRCULAR 77-16, EMERGENCY DIESEL GENERATOR ELECTRICAL TRIP LOCK-OUT FEATURES 

The subject document is transmitted for issuance on December 13, 1977. The 
Circular should be issued to all holders of Reactor Operating Licenses and 
Construction Permits. Also enclosed is a draft copy of the transmittal 
letter. 

                                   Harold D. Thornburg, Director 
                                   Division of Reactor Operations  
                                     Inspection 
                                   Office of Inspection and  
                                     Enforcement 

Enclosures: 
1. Circular 77-16 
2. Draft Transmittal Letter 

CONTACT:  V. D. Thomas, IE 
          49-28180 
.

Transmittal letter for Circular 77-16, to each holder of an NRC Operating 
License and Construction Permit. 

Addressee: 

The enclosed Circular 77-16, is forwarded to you for information. If there 
are any questions related to your understanding of the suggested actions, 
please contact this office. 


                                   Signature 
                                   (Regional Director) 

Enclosure: 
IE Circular 77-16 
.

                     NUCLEAR REGULATORY COMMISSION 
                   OFFICE OF INSPECTION AND ENFORCEMENT 
                          WASHINGTON, D.C. 20555 

                             December 9, 1977 

                                                         IE Circular 77-16 

EMERGENCY DIESEL GENERATOR ELECTRICAL TRIP LOCK-OUT FEATURES 

Description of Circumstances: 

On June 15, 1977, Duquesne Light Company (Beaver Valley 1) reported that 
during the performance of a test of the diesel-generator (D/G) trip lock-out
features in the emergency mode of operation, the D/G output circuit breaker 
opened when the field voltage trip interlock was tested. This is contrary to
a requirement for this facility that, in the emergency mode, all D/G output 
breaker trips except generator differential and overcurrent be automatically
disabled. The engine overspeed trip, which shuts down the diesel engine (but
does not affect breaker operation) is also expected to be operable during 
the emergency mode of operation. 

An investigation conducted by the licensee disclosed that the unexpected 
opening of the output breaker was due to deenergizing a field voltage 
sensing relay which was supplied by the vendor but had not been disconnected 
during the on-site acceptance testing of the D/G nor disabled by the 
protection circuitry logic. A redundant field voltage relay which was 
supplied by the licensee is correctly by-passed during fast start conditions 
and emergency operation. 

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IE Circular 77-16                                     December 9, 1977 

A design change was initiated by the licensee which removed the field 
voltage trip feature. This was accomplished by disconnecting the set of 
relay contacts to the trip circuitry of the D/G output breaker. Subsequent 
testing of the D/G was performed by the licensee which demonstrated 
satisfactory operation. 

This is an example of an event which resulted from inadequate test procedure
performance. The procedures as performed had not previously identified the 
type of deficiency described in this circular. 

The safety significance of this situation is that the premodified protection
circuitry would have opened the circuit breaker if a loss of field voltage 
occurred while running in the emergency mode of operation. 

The D/G Units for the above facility were supplied by the Electro Motive 
Division (EMD) of General Motors. The model numbers for the D/G Units are: 

     Engine Model No. 20-645-E4 
     Generator Model No. A-20-C2 
     Control Panel Model No. 999-20 

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IE Circular 77-16                                          December 9, 1977 

All holders of operating licenses or construction permits should assure that
the appropriate D/G protection trip circuits are provided with automatic 
by-pass features that prevent them from negating automatic starting or 
tripping of D/Gs during fast start or emergency operations. It is 
recommended that the following be considered in your reviews of this matter: 

1.   Facility procedures should specifically determine whether the 
     protection circuitry that trips the D/G set or the associated output 
     breaker is in accordance with the facility Technical Specifications. 
     
2.   Test procedures for your D/G sets (e.g. acceptance preoperational and 
     surveillance tests) should be reviewed to assure that D/G system 
     performance is demonstrated by these tests to be in accordance with 
     related operational requirements specified in the facility Technical 
     Specifications. 

3.   Strengthening of management controls should be reviewed as necessary to
     assure adherence to D/G test procedures by plant personnel. 

No written response to this circular is required. If you require additional 
information regarding this matter, contact the Director of the appropriate 
NRC Regional Office. 

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