United States Nuclear Regulatory Commission - Protecting People and the Environment

Bulletin 85-01: Steam Binding of Auxiliary Feedwater Pumps

                                                  OMB No.: 3150-0011  
                                                  Expiration Date: 9/30/86 
                                                  IEB 85-01 

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

                              October 29, 1985

IE BULLETIN 85-01: STEAM BINDING OF AUXILIARY FEEDWATER PUMPS 

Addressees: 

For Action - Those nuclear power reactor facility licensees and construction
permit (CP) holders listed in Attachment 1. 

For Information - All other nuclear power reactor facilities. 

Purpose: 

The purpose of this bulletin is to inform licensees and CP holders of a 
potentially serious safety problem that has occurred at certain operating 
facilities involving the inoperability of auxiliary feedwater (AFW) pumps as
a result of steam binding. Certain PWR licensees and all PWR CP holders are 
requested to take further action to prevent similar events from occurring at
their facilities and to document those actions taken or planned. 

Description of Circumstances: 

Numerous events have been reported where hot water has leaked into AFW 
systems and flashed to steam, disabling the AFW pumps. Events at Robinson 2 
in 1981 through 1983, Crystal River 3 in 1982 and 1983, and D. C. Cook 2 in 
1981 were summarized in IE Information Notice (IN) 84-06, issued in January 
1984. Also in January 1984, the Institute of Nuclear Power Operations (INPO)
issued Significant Event Report (SER) 5-84 detailing events at Robinson 2 
and Farley. In April 1984, INPO issued Significant Operating Experience 
Report (SOER) 84-3 that discussed another event at Surry 2 in 1983. 

The NRC's Office for Analysis and Evaluation of Operational Data (AEOD) 
issued a case study report entitled "Steam Binding of Auxiliary Feedwater 
Pumps" in July 1984. This study identified 22 events since 1981; 13 of these
occurring in 1983. Based on operating experience, it appears that 
backleakage into AFW could occur in any PWR. In a number of plants, the two 
motor-driven pumps feed into a single pipe which feeds into the steam 
generator; therefore, a leaking valve in that pipe increases the probability 
of steam binding in both trains of AFW. Also, multiple AFW pumps often take 
suction from a common manifold; therefore, if one pump becomes steam bound 
because of leaking check valves, the steam can heat the common suction and 
cause other pumps to become steam bound. 



8510250539 
.

                                                            IEB 85-01 
                                                            October 29, 1985 
                                                            Page 2 of 4 

AFW capability is needed for normal shutdown and transient conditions as 
well as for accident mitigation. The AEOD case study examined the effects of 
steam binding on a sequence in which there was a loss of the power 
conversion (steam generation) system after a transient other than 
loss-of-offsite power. A probabilistic risk analysis had previously shown 
this sequence to be a dominant contributor to the core-melt risk for a 
sample plant (Sequoyah). The case study indicated that unavailability of the 
AFW system as a result of steam binding contributes significantly to the 
risk of core melt in PWRs. Monitoring AFW to detect backleakage and to 
promptly correct the situation if backleakage occurs would reduce the 
probability of steam binding. 

Since the AEOD study was issued, a series of events involving backflow of 
hot water into the AFW system occurred at McGuire 2 over a period of 7 days 
in August 1984, before effective corrective action was taken. One of these 
events involved overpressurization of the suction line and damage to 
instruments. In November 1984, Catawba 1 experienced backflow of hot water 
into AFW resulting in fumes from insulation and blistering of paint. In 
December 1984, the NRC's Office of Nuclear Reactor Regulation (NRR) 
determined that steam binding of AFW was a generic issue and assigned it a 
high priority (Generic Issue 93, "Steam Binding of Auxiliary Feedwater 
Pumps"). 

To determine the extent of the safety issue and the need for short-term 
corrective actions, the NRC's regional offices conducted a survey in April 
and May of 1985. Of the 58 operating reactors surveyed, 39 had temperature 
monitoring of AFW piping at least once per shift. Of the remaining 19, 17 
had normally closed gate or globe valves in the pump discharge path in 
addition to check valves, or some unique feature such as complete separation 
of trains that made serious safety problems unlikely. The remaining 2 
licensees have subsequently decided to monitor AFW piping temperature. 

Although some degree of action has been taken at all units, many have not 
incorporated these actions into procedures to detect or correct steam 
binding. Without these provisions, there is little assurance that effective 
actions will continue. For this reason, the addressees are requested to take
the following actions: 

Action for Addressees Listed in Attachment 1 

1.   Develop procedures for monitoring fluid conditions within the AFW 
     system on a regular basis during times when the system is required to 
     be operable. This monitoring should ensure that fluid temperature at 
     the AFW pump discharge is maintained at about ambient temperature. 
     Monitoring of fluid conditions, if used as the primary basis for 
     precluding steam binding, is recommended each shift.

     This item is not intended to require elaborate instrumentation. A 
     simple means of monitoring temperature, such as touching the pipe, is a 
     satisfactory approach.

2.   Develop procedures for recognizing steam binding and for restoring the 
     AFW system to operable status, should steam binding occur.
.

                                                            IEB 85-01  
                                                            October 29, 1985 
                                                            Page 3 of 4 

3.   Procedural controls should remain in effect until completion of 
     hardware modification to substantially reduce the likelihood of steam 
     binding or until superseded by action implemented as a result of 
     resolution of Generic Issue 93. 

Schedule: For operating plants, develop and implement procedures within 90 
days of the date of this bulletin. For plants under construction, develop 
and implement procedures within 90 days after receiving an operating license 
or provide an appropriate response and commitment within 1 year of the date 
of this bulletin, whichever comes first. 

Reporting Requirements: Prepare and submit a report describing the methods 
used to accomplish these actions. Include the date(s) that procedures and 
training were implemented or scheduled to be implemented. State the 
frequency of monitoring of the temperature. For operating plants, submit 
this report within 120 days of the date of this bulletin. For plants under 
construction, submit the report within 120 days after receiving an operating 
license or within 1 year of the date of this bulletin, whichever comes 
first. It is not necessary to submit the procedures for review. 

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

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

Although no specific request or requirement is intended, the following 
information would be helpful to the NRC in evaluating the cost of this 
bulletin: 

     1.   staff time to perform requested review and testing 

     2.   staff time to prepare requested documentation 
.

                                                            IEB 85-01 
                                                            October 29, 1985 
                                                            Page 4 of 4 

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


                              James M. Taylor, Director 
                              Office of Inspection and Enforcement 

Technical Contacts: Mary S. Wegner, IE 
                    (301) 492-4511 

                    C. Vernon Hodge, IE 
                    (301) 492-7275 

Attachments: 
1. Addressees for Action 
2. List of Recently Issued IE Bulletins 
Page Last Reviewed/Updated Tuesday, July 23, 2013