United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 84-58: Inadvertent Defeat of Safety Function Caused by Human Error Involving Wrong Unit, Wrong Train, or Wrong System

                                                            SSINS No.: 6835 
                                                            IN 84-58       

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

                                July 25, 1984

Information Notice No. 84-58:   INADVERTENT DEFEAT OF SAFETY FUNCTION 
                                   CAUSED BY HUMAN ERROR INVOLVING WRONG 
                                   UNIT, WRONG TRAIN, OR WRONG SYSTEM 

Addressees: 

All nuclear 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 inadvertent defeat of safety functions 
caused by human errors involving the wrong unit, wrong train, or wrong 
system. It is expected that recipients will review 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: 

A large number of reports have been made to the NRC that describe events in 
which safety functions were inadvertently defeated as a result of actions 
performed on the wrong unit of a multi-unit plant, the wrong train of 
systems with redundant trains, or a wrong system. In many cases, the loss of 
safety function was not recognized for a long period of time, resulting in 
significant degradation of the levels of safety. An example of each type of 
event, caused by human error involving the wrong unit, wrong train or wrong 
system, is described below. A sample listing from among at least 50 reports 
of other similar events that have occurred is contained in Table 1. 

On October 2, 1983, an operator was dispatched to lock closed a manual valve
on the discharge side of each of the redundant containment spray pumps for 
Turkey Point Unit 3. The activity was required by the procedure for 
proceeding from hot to cold shutdown in preparation for a refueling outage. 
The operator, instead of closing the Unit 3 valves, locked closed the valves
for Unit 4 which was operating at power. Subsequent to this activity, there 
was a change in operators. The replacement operator later went to the Unit 3 
containment spray pump discharge valves and closed them as he found them to 
be open. He was 



8407230079 
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unaware that the Unit 4 valves were closed. It was over a day later before 
the licensee's technical staff discovered the Unit 4 valves to be locked 
closed during a monthly periodic test of the containment spray system. 

Hatch Unit 2 was operating at 100% power on August,17, 1982, with the "B" 
loop of the residual heat removal service water system (RHRSWS) out of 
service for maintenance. While removing "B" loop from service, the personnel
tasked with closing the "B" loop strainer inlet valve inadvertently closed 
the "A" loop strainer inlet. This resulted in the total loss of RHRSWS and, 
thus, the residual heat removal (RHR) system including the postaccident heat
removal capability. 

On February 7, 1984, the FitzPatrick plant was operating at full power when 
the high-pressure coolant injection (HPCI) system was intentionally tagged 
out of service to permit general maintenance and modification of the 
overspeed trip. Tagging out the HPCI system included closing of the motor 
operated steam supply valves, and racking out the breakers for the valves 
and oil pumps for the turbine. Before removing HPCI from service, other 
safety systems were demonstrated operable as required by the Technical 
Specifications. As a part of the maintenance, technicians were assigned to 
calibrate the HPCI turbine speed indication which involved disconnecting the
speed feedback circuit and thus disabling the HPCI system regardless of any 
other actions. After completing the calibration on what they thought to be 
the HPCI turbine speed instrumentation, the technicians reported that the 
as-found tolerance was over 40% higher than the procedure limit. When the 
responsible supervisor initiated an investigation of the as-found tolerance,
it was discovered that the technicians had calibrated the reactor core 
isolation cooling (RCIC) speed instrumentation instead of the HPCI 
instrumentation. This activity had resulted in loss of RCIC with HPCI 
unavailable. 

Discussion: 

A review of the inadvertent defeat of safety function events including those
cited above and summarized in Table 1, indicates that many events were 
highly significant from the standpoint of safety and others would have been 
significant if they had occurred under different circumstances. The review 
also indicates that misidentification of equipment by personnel was the 
primary cause of most events. Other events were caused by inadequate 
planning, defective procedures, or defective labeling of equipment. Although
not the primary cause, design error or failure to perform adequate 
verification of activities was a contributing factor in some events. 

In the Turkey Point event, the operator had access to the wrong unit because
the access keys were the same for the two units. Also, the valves had 
identical identification tags for both units. The operator did not carry the
tag out sheet with him and thus did not sign it for completion of the 
activity. Later, the replacement operator closed the correct valves. The 
closed valves on the operating unit were not discovered for over 28 hours 
because no verification of the activities was performed. Following the 
event, the procedural and administrative deficiencies were corrected. A 
walkdown of the accessible portions of all safety-related flow paths was 
performed to verify that all valves were in correct positions, the locks for 
the two units were color coded, and different keys were made for the locks 
of the two units. 
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                                                             IN 84-58     
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                                                             Page 3 of 3  

The Hatch Unit 2 event was attributed to personnel error and lack of 
adequate independent verification. As a part of corrective actions, new 
identification tags were made and locks were changed so that the, keys for 
valves in one loop will not open the valves in the other loop. In addition, 
the personnel responsible were counseled and reprimanded. 

The FitzPatrick loss of RCIC event with HPCI out of service was caused by 
personnel error. Following the event, the licensee instituted an awareness 
program for the technicians in addition to improving the identification of 
HPCI and RCIC equipment. 

Adequate procedures, planning, labeling, awareness and training of 
personnel, and an independent verification program are needed to prevent the 
occurrences of such events. The frequency and number of such events being 
reported to the NRC indicates a need for further industry action in these 
areas. Additional guidance on independent verification programs is provided 
in Information Notice No. 84-51, "Independent Verification." 

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 

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

Attachment
1.   Sample List of Recent Inadvertent
       Defeat of Safety Function Events
2.   List of Recently Issued IE Information Notices
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                                                             Page 1 of 1  


                Table 1: Sample List of Inadvertent Defeat 
                         of Safety Function Events

Plant/Date                      Event Summary

D.C. Cook                       An auxiliary equipment operator was 
03/14/81                        instructed to deenergize breakers for five 
                                motor operated valves of the Unit 2 safety 
                                injection system. He instead deenergized the
                                breakers of five Unit 1 valves. 

Calvert Cliffs                  Electricians began work on Unit 2 control 
04/17/82                        element assemblies (CEAs) instead of the 
                                assigned Unit 1 CEAs. 

Point Beach                     An operator was instructed to perform part 
04/22/82                        of a procedure to drain the reactor coolant 
                                of Unit 2 which was shutdown. Instead, he 
                                performed the procedure steps on operating 
                                Unit 1. 

North Anna 2                    Both trains of the quench spray subsystem 
05/28/82                        and the recirculation spray system were made
                                inoperable because jumpers were installed in
                                the train "A" instead of the train "B" solid
                                state protection output cabinet. 

St. Lucie 1                     During full power operation, the primary and
06/29/83                        back up heat tracing for the boron injection
                                flow paths were isolated for 24 hours. The 
                                condition existed because the entire 
                                chemical and volume control system heat 
                                tracing was isolated rather than only that 
                                required for the "A" boric acid piping. 

Turkey Point 3                  With the unit at 100% power and auxiliary 
04/19/83                        feed water pump "A" out of service, all 
                                steam supply valves for "B" and "C" pumps 
                                were found to have been closed for five 
                                days. The operators had misidentified the 
                                valves and independent verification was not 
                                performed. 

D.C. Cook 2                     During containment spray system testing, 
06/03/83                        operators closed a wrong valve which 
                                rendered the train not under test 
                                inoperable. 

Kewaunee                        Both trains of shield building ventilation 
03/13/84                        were taken out of service for one hour when 
                                maintenance personnel began work on the "A" 
                                train instead of the "B" train. 
Page Last Reviewed/Updated Tuesday, November 12, 2013