United States Nuclear Regulatory Commission - Protecting People and the Environment

Bulletin 86-03: Potential Failure of Multiple Eccs Pumps Due to Single Failure of Air-operated Valve in Minimum Flow Recirculation Line

                                                       SSINS No.: 6820 
                                                       OMB No.: 3150-0011
                                                       IEB 86-03

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

                               October 8, 1986

IE COMPLIANCE BULLETIN NO. 86-03:  POTENTIAL FAILURE OF MULTIPLE ECCS PUMPS 
                                   DUE TO SINGLE FAILURE OF AIR-OPERATED 
                                   VALVE IN MINIMUM FLOW RECIRCULATION LINE 

Addressees: 

All facilities holding an operating license or a construction permit. 

Purpose: 

The purposes of this bulletin are (1) to inform addressees of single 
failures of minimum flow recirculation lines containing air-operated 
isolation valves which could result in a common-cause failure of all 
emergency core cooling system (ECCS) pumps in a system, (2) to request that 
licensees affected by the problem promptly provide appropriate instructions 
and training to plant operators on how to recognize the problem if it occurs 
and take appropriate mitigating actions, (3) to request that licensees 
notify the NRC concerning the existence of the problem at their facility, 
and (4) to request that licensees inform the NRC of measures taken to 
correct this and/or other significant problems that are identified as a 
result of this bulletin. 

Description of Circumstances: 

There have been four recent cases where a design deficiency has been found 
involving the minimum flow recirculation paths for ECCS pumps. Although 
these four cases all involve safety injection (SI) pumps in 
Westinghouse-designed reactors, similar problems also could exist in other 
systems and at other types of reactors. This design deficiency was first 
discovered at the Point Beach Nuclear Plant and was subsequently described 
in IE Inforation Notice 85-94. A similar problem involving residual heat 
removal (RHR) system loop selection logic was later found in several BWR 
plants. This problem was addressed in IE Compliance Bulletin 86-01. 

On July 24, 1985, Wisconsin Electric Company submitted a report in 
accordance with 10 CFR Part 21 for the Point Beach Nuclear Plant describing 
a design deficiency involving the minimum flow recirculation valves for the 
SI pumps. At Point Beach the discharge lines for each of the SI pumps are 
connected to a common recirculation header to provide a test flow path and a 
recirculation flow path for minimum flow at times when the reactor coolant 
system (RCS) pressure exceeds the SI pump shutoff head. The common 
recirculation header is provided with two air-operated valves in series. 
These valves close to isolate the 

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                                                          IEB 86-03 
                                                          October 8, 1986
                                                          Page 2 of 3


refueling water storage tank (RWST) from the containment sump during the 
recirculation phase of emergency core cooling following a postulated 
loss-of-coolant accident (LOCA). Closure of these valves is intended to 
prevent containment reactor coolant from being pumped outside containment to
the RWST during the recirculation phase. Both of the recirculation header 
isolation valves are designed to fail closed when their control circuits 
lose electrical power or control air pressure. The Part 21 report noted that 
a single failure (open) of the breaker associated with either of the two 
valves would isolate the minimum flow path for both SI pumps, defeat the 
control room remote operation capability of the affected valve, and cause 
the loss of control room valve position indication. 

On February 5, 1986, Carolina Power and Light submitted LER 86-01 describing
essentially the identical design deficiency involving the minimum flow 
recirculation path for the SI pumps at H. B. Robinson. On June 20, 1986, 
Rochester Gas and Electric discovered a similar design deficiency at the 
Ginna Plant and on June 25, 1986, Florida Power and Light Company reported a 
similar design deficiency at the Turkey Point Plant. 

The concern in all four cases above involves a postulated small break LOCA 
which initiates a safety injection signal that starts the SI pumps. During a 
small break LOCA, RCS pressure may not readily decrease below the SI pump 
shutoff head. A single failure resulting in the loss of the minimum flow 
path concurrent with SI pump actuation would cause the pumps to operate 
deadheaded until RCS pressure decayed below the SI pump shutoff head. The 
simultaneous loss of minimum flow valve position indication in the control 
room will exacerbate this loss of minimum flow path. The availability of 
valve position indication is not expected to sufficiently ameliorate this 
event. Operating the SI pumps deadheaded would result in pump damage and 
failure within a few minutes. The failure of multiple trains in an ECCS due 
to a single failure violates the single failure criterion in General Design 
Criterion (GDC) 35 (10 CFR 50, Appendix A). In all the above cases, the 
short-term corrective actions taken by the licensees were to mechanically 
block open the SI pump recirculation valves to ensure a minimum flow path 
and to revise the applicable plant LOCA procedures to manually close these 
valves prior to switching to the recirculation mode. This short term action 
should be carefully weighed against the requirements to minimize containment 
leak paths in the ECCS recirculation mode of operations and the reliability 
of operator actions in this regard. 

Actions Required:* 

1.   Promptly determine whether or not your facility has a single-failure 
     vulnerability in the minimum flow recirculation line of any ECCS pumps 
     that could cause a failure of more than one ECCS train. 

2.   If the problem exists: (a) promptly instruct all operating shifts of 
     the problem and measures to recognize and mitigate the problem; (b) 
     promptly develop and implement corrective actions which bring your 
     facility into compliance with GDC 35. 


*Actions required of the BWR plants in response to IE Compliance Bulletin 
86-01 need not be repeated in responding to this Bulletin. 
.

                                                           IEB 86-03
                                                           October 8, 1986
                                                           Page 3 of 3

3.   Within 30 days of receipt of this bulletin, (a) provide a written 
     report to the NRC which identifies whether or not this problem exists 
     at your facility, (b) if the problem exists (or existed), include in 
     the report the justification for continued operation and identify the 
     short-term modifications to plant operating procedures or hardware that 
     have been or are being implemented to ensure safe plant operations. 

4.   If the problem exists (or existed), provide a written report within 90 
     days of receipt of this bulletin informing the NRC of the schedule for 
     long-term resolution of this and/or any other significant problems that
     are identified as a result of this bulletin. 

The written report shall be submitted to the appropriate Regional 
Administrator under oath or affirmation under provisions of Section 182a, 
Atomic Energy Act of 1954, as amended. Also, the original copy of the cover 
letter and a copy of the report shall be transmitted to the U.S. Nuclear 
Regulatory Commission, Document Control Desk, Washington, D.C. 20555 for 
reproduction and distribution. 

This request for information was approved by the Office of Management and 
Budget under blanket clearance number 3150-0011. Comments on burden and 
duplication may be directed to the Office of Management and Budget, Reports 
Management, Room 3208, New Executive Office Building, Washington, D.C. 
20503. 

If you have questions regarding this matter, please contact the Regional 
Administrator of the appropriate NRC regional office or one of the technical
contacts listed below. 




                              James M. Taylor, Director
                              Office  of Inspection and Enforcement

Technical Contact:  Henry Bailey, IE 
                    (301) 492-9006 

                    Ron Young, IE 
                    (301) 492-8985 

Attachment:    List of Recently Issued IE Bulletins 
Page Last Reviewed/Updated Tuesday, July 23, 2013