United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 84-48: Failures of Rockwell International Globe Valves

                                                            SSINS No.: 6835 
                                                                   IN 84-48 

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

                                June 18, 1984

Information Notice No. NO- 84-48:   FAILURES OF ROCKWELL INTERNATIONAL GLOBE 
                                   VALVES 

Addressees: 

All nuclear power reactor facilities holding an operating, license (OL) or a 
construction permit (CP). 

Purpose: 

The intent of this information notice is to alert licensees of a potential 
deficiency in the design, application, or maintenance of Rockwell 
International globe valves that may have safety and/or economic significance
at nuclear power facilities. These deficiencies have resulted in two types 
of failures: (1) the stem separating from the disk and (2) the disk being 
backed off its disk nut (see Attachment 1). Although no specific action or 
response is required, recipients are expected to review the information 
contained in this notice for applicability to their facilities and initiate 
any needed diagnostic, preventive, or corrective action. Likewise, licensees
finding similar or related defects at their facilities are encouraged to 
report their findings to the Commission, including the corrective actions 
taken, so that the industry may benefit from their experience. However, 
suggestions contained in this information notice do not constitute NRC 
requirements and, therefore, no specific action or written response is 
required. 

Background: 

The discovery of these failures is attributed to what appeared to be a 
completely unrelated event described in Information Notice No. 83-65, 
"Surveillance of Flow in RTD Bypass Loops Used in Westinghouse Plants" 
(dated October 7, 1983) and the sharing of information by two utilities. 
Information Notice 83-65 was issued because of a low-flow condition in a 
reactor coolant loop RTD bypass line that occurred at Salem Unit 1. The 
manner by which this apparently unrelated event led to the discovery of the 
described globe valve failures is described below. 

Description of Circumstances: 

On January 29, 1983, during routine shutdown operations, a low-flow alarm 
was received from a reactor coolant loop RTD bypass line at Salem Unit 1. 
Investigation of the event led to the assumption that corrosion products 
were restricting flow in the bypass line. This event was reported in 
Licensee Event 

8406180353 
.

                                                              IN 84-48     
                                                              June 18, 1984 
                                                              Page 2 of 3  

Report (LER) 83-007/31 which in turn resulted in the NRC issuing IE 
Information Notice 83-65. Because no previous surveillance requirements 
existed, the information notice recommended that the flow sensors be 
calibrated on a refueling outage basis and that the alarm set point be 
verified on a monthly basis. 

As a result of the above cited notice, Salem received information from 
Kewaunee, through the Westinghouse site representative, informing them of a 
similar reduced flow problem experienced at Kewaunee. The Kewaunee problem 
was caused by a stem-to-disk separation of a bypass line isolation valve. 
The valve disk had fallen, resulting in restriction of RTD bypass loop flow.
Given the right conditions, the valve disk could lift and flow would be 
reestablished such that the failure could easily be mistaken for an 
obstruction caused by crud. (It should be noted that these failures can 
occur and be undetected during operation.) 

Although the January 1983 occurrence of reduced flow was the only one of its
kind experienced at either of the Salem units, Salem decided to radiograph 
all RTD bypass line valves in all reactor coolant loops of both units during
their next refueling outages. During a January 1984 outage, the Unit 2 RTD 
bypass line valves were radiographed. Five valves in each of the four bypass
lines were radiographed indicating that 2 of the 20 valves had disks that 
had separated from the stems. Because of a large flow margin, these valves 
were not replaced; however, to assure that flow blockage has not occurred, 
the licensee has increased the frequency of flow surveillance. Salem 
attributes the separation of the stem from the disk to the force exerted on 
the joint when the valve is backseated. Accordingly, Salem has advised their 
operators to use caution while backseating these types of valves. During the 
April, 1984 refueling outage, the Unit 1 RTD bypass line valves were 
radiographed, and 11 of the 20 valves were found with their disks separated 
from the stems. All 20 RTD bypass line valves in Unit 1 were replaced. 

Because of the generic implications associated with the failures of Rockwell
International globe valves, Salem undertook to examine a sample of similar 
valves used in critical systems. On or about May 25, 1984, similar valves 
used as throttle valves in the high pressure safety injection subsystem of 
the emergency core cooling system on Unit 1 were radiographed. The unit was 
in a refueling outage at the time and 1 of the 12 throttle valves was found 
with its disk backed off the disk nut. As a result of this discovery, Salem 
also radiographed the Unit 2 throttle valves while the plant was operating 
at 100% power. On May 30, 1984, two of these valves were found with the 
disks backed off the disk nut. Because proper flow through these valves 
could not be ensured, the valves were declared inoperable. Consequently, the 
plant was placed in an action statement that required the valves to be 
operable or to be in a hot shutdown mode within 6 hours. These throttle 
valves are 1-1/2 inch Rockwell International globe valves and are set during 
surveillance testing once per 18 months to ensure that flow from the boron 
injection tank is properly distributed to each of the four cold legs during 
safety injection. The licensee has removed, replaced and inspected the 3 
throttle valves having disks that had backed off their disk nut. The 
inspection revealed that in each case the lock weld attaching the disk to 
the disk nut was missing and that a portion 
.

                                                            IN 84-48 
                                                            June 18, 1984 
                                                            Page 3 of 3 

of the lower disk guide was broken off in the same location relative to the 
lock weld holding the disk. Consequently, the licensee believes that the 
disk became partially unthreaded from the disk nut during those periods when 
the valves are closed for flow blocking purposes during shutdown and then 
opened. To assure proper positioning of the disks, the licensee plans to 
radiograph the valves after any valve movement. 

No action or written response to this notice is required. 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:  I. Villalva
                    (301) 492-9635

                    R. Kiessel
                    (301) 492-8119

Attachments:
1.   Cross-section, Rockwell Globe Valve
2.   List of Recently Issued IE Information Notices

Page Last Reviewed/Updated Tuesday, November 12, 2013