United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 86-19: Reactor Coolant Pump Shaft Failure at Crystal River

                                                           SSINS No: 6835 
                                                           IN 86-19       

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

                               March 21, 1986

Information Notice No. NO 86-19:   REACTOR COOLANT PUMP SHAFT FAILURE AT 
                                   CRYSTAL RIVER 

Addressees: 

All nuclear Power reactor facilities holding an operating license (OL) or a 
construction permit (cp) 

Purpose: 

This information notice provides notification of failure of reactor coolant 
pump shafts manufactured by Byron-Jackson (BJ) Company It is expected that 
recipients will review the information for applicability to their facilities 
and consider actions, if appropriate, to detect a similar problem at their 
facilities However, suggestions contained in this notice do not constitute 
NRC requirements; therefore, no specific action or written response is 
required 

NRC is continuing to obtain and evaluate pertinent information If specific 
actions are determined to be required by NRC, an additional communication 
will be issued 

Description of Circumstances: 

On January 1, 1986, the Crystal River Unit 3 (CR-3) reactor tripped because 
of low flow in reactor coolant system loop A Just before the reactor trip 
occurred, the reactor coolant pump (RCP) motor frame vibration monitor 
showed high vibration This was followed by a RCP thrust bearing upper shoes 
high temperature alarm (which activates at temperatures greater than 
185F) The licensee manually tripped the RCP motor, which resulted in a 
reactor trip On January 4, 1986, the licensee entered the reactor building 
to inspect the RCP and found no evidence to indicate that the pump had 
sustained damage 

On January 6, 1986, the licensee began preliminary troubleshooting on loop A 
RCP motor shaft, coupling, and seal cover Following these checks, the pump 
shaft was uncoupled from the motor and an unsuccessful attempt was made to 
rotate the pump shaft Also, various attempts to raise the shaft with 
hydraulic pressure failed 

On January 14, 1986, an ultrasonic examination of the shaft in place 
identified a major reflector at a distance of approximately 50 in from the 
top The 



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                                                            Page 2 of 3   

reflector was evident throughout the entire circumference of the shaft 
Finally, on January 15, 1986, after having lifted the RCP motor and removed 
other interferences, the licensee removed the upper shaft remnant from the 
pump Preliminary visual inspection of the removed shaft section showed that 
the fracture occurred in the location of a machined, flat-bottom 
circumferential groove measuring approximately 0375 in x 0200 in This 
groove is located just below the multigroove section on the shaft that is 
identified as a thermal barrier 

Other operating units with essentially identical pumps are Davis-Besse and 
Arkansas Unit 1 Both these sites have been notified of the findings at 
Crystal River At Davis-Besse, currently in an extended outage, the licensee 
performed similar UT examinations and reports confirmed cracking in one 
shaft, with probable cracks in the other three The licensee has ordered 
four replacement shafts Arkansas Unit 1 has also ordered four replacement 
shafts (about 12 week delivery) and plans to continue in operation pending 
delivery Midland Units 1 and 2 have the same pumps, but work is currently 
suspended on these partially constructed facilities 

Discussions with cognizant Crystal River personnel disclosed that currently 
the groove in question serves no functional purpose on the shaft assembly 
It is NRC's understanding that this groove was intended for a split ring 
that was deleted by a design change after the groove had been machined in 
the shaft All four pumps at CR-3 have shafts with this machined-in groove 
Following verification of the shaft's failure, the licensee conducted an 
ultrasonic examination of the three remaining RC pump shafts and determined 
that the shaft in RCP B exhibited circumferential crack indications in the 
same location as RCP A The indications exceeded minimum calibration notch 
depth dimensions of 0226 in and were noted from 180 to 200 
around the circumference Subsequently, PT confirmed the crack in the pump B 
shaft Ultrasonic examination of the C and D pump shafts showed indications 
of cracks As a result, all four shafts are being replaced 

The failed shaft(s) were made from precipitation hardening stainless steel 
material produced to ASTM Specification A461-65 Grade 660 requirements and 
inspected per ASME Section III (68,S69), paragraph N-3221, N-627 

Currently, the licensee attributes the shaft failure on pump A at Crystal 
River to residual fabrication stresses coupled with thermal stresses from 
cool seal water injection The pump B shaft crack is being attributed to 
local assembly weld stresses compounded by thermal stresses The shaft 
material is difficult to weld successfully 


                                                            IN 86-19      
                                                            March 21, 1986 
                                                            Page 3 of 3   

A metallurgical investigation is being conducted by Babcock and Wilcox 
(B&W), Lynchburg, Virginia, to determine the cause of failure Region II 
metallurgical staff is following up this investigation To date, the only 
information from this investigation is that in pump A all four socket head 
capscrews that join the shaft and impeller were found to be broken Two 
alignment pins were not broken Further information on shaft B is not yet 
available, other than the cap screws on pump B assembly were either cracked 
or broken 

The cap screw failures are attributed to intergranular stress corrosion 
cracking (IGSCC) 

A similar event involving the capscrews in a BJ pump at the Palisades 
nuclear plant is discussed in Information Notice 85-03 and Supplement 1 to 
that information notice The pumps at Palisades are a different size from 
those at Crystal River, but the designs are apparently similar 

At Palisades, the shaft did not fail but separated from the impeller The 
shaft is normally secured by eight sockethead capscrews and four alignment 
pins All eight capscrews and two of the four alignment pins were broken 
The two other pins were distorted The cause of failure was stated to be 
insufficient preload on the capscrews caused by rough threads, which 
resulted in the prescribed tightening torque not achieving the desired 
preload 

No specific action or written response is required by this information 
notice If you have any questions about this matter, please contact the 
Regional Administrator of the appropriate regional office or this office 




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

Technical Contact:  Jim Henderson, IE
                    (301) 492-9654

                    Nick Economos, RII
                    (404) 331-5580

Attachment: List of Recently Issued IE Information Notices

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