Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
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
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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
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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
