United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 86-72: Failure 17-7 PH Stainless Steel Springs in Valcor Valves due to Hydrogen Embrittlement

                                                            SSINS No.: 6835 
                                                            IN 86-72       

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

                               August 19, 1986

Information Notice No. 86-72:   FAILURE 17-7 PH STAINLESS STEEL SPRINGS 
                                   IN VALCOR VALVES DUE TO HYDROGEN 
                                   EMBRITTLEMENT 

Addressees: 

All nuclear power reactor facilities holding an operating license or a 
construction permit. 

Purpose: 

This notice is provided to inform recipients of a potentially significant 
safety problem that could result from the failure of springs in solenoid 
globe valves manufactured by Valcor Engineering Corporation. According to 
the valve manufacturer these valve springs may fail when exposed to high 
temperature reactor coolant containing hydrogen. 

It is expected that recipients will review the information for applicability
to their facilities and consider action, as appropriate, to preclude a 
similar problem from occurring at their facility. However, suggestions 
contained in this information notice do not constitute NRC requirements; 
therefore, no specific action or written response is required. 

Description of Circumstances: 

Difficulties were experienced with the operability of two solenoid-operated 
globe valves (Model V526-6190A, p/n 454660001) in the charging system at the
Fort Calhoun Station, Unit 1 in August 1985. When shut, the valves could not
be reopened without securing all charging pumps. During a refueling outage 
in January 1986, the two valves were disassembled and examined to determine 
the cause of the valve malfunction. It was found that disc guide assembly 
springs in both valves had undergone complete and catastrophic failure. The 
springs, which initially had 25 coils, were found in sections of only 1-2 
coils. Metallurgical analysis of the failed springs attributed the probable 
cause of failure was due to hydrogen embrittlement. The spring is made of 
17-7 PH stainless steel. 

Discussion with the valve manufacturer, Valcor Engineering Corporation, 
revealed that during 1982-83 one failure occurred at Prairie Island Nuclear 
Generating Station and two failures occurred at North Anna Nuclear 
Generating Station. These spring failures were also attributed to hydrogen 
embrittlement. 
.

                                                           IN 86-72 
                                                           August 19, 1986 
                                                           Page 2 of 2


Discussion: 

Based on analysis and evaluation of the earlier spring failures, the valve 
manufacturer issued a letter in 1983 to affected licensees requesting 
information on valve application and advised customers of a potential spring
problem. Elgiloy springs were offered on receipt of information confirming 
use with reactor chemistry fluid or specific customer request. With the 
occurrence of the third similar event, the valve manufacturer is planning to
issue a second letter to affected licensees conservatively recommending that
valves with spring material of 17-7 PH stainless steel used in borated water
or reactor chemistry water be closely monitored and evaluated for any change
in normal operation such as increased seat leakage or an increase in the 
time required to change position. These conditions could be attributed to 
broken springs. The manufacturer has concluded that hydrogen embrittlement 
of stainless steel springs is a complex function of high temperature, water 
chemistry, water flow condition, and time of exposure to the service 
condition. Therefore, all such springs made of 17-7 PH stainless steel used 
in Valcor valves in nuclear power plant may be susceptible to this failure 
mode under these conditions and should be considered for replacement. 

The above described events are an indication of potential licensee/vendor 
interface problem. Based on the information received by the NRC, the vendor 
was not completely informed via the purchase specifications regarding the 
service condition to which the valve would be exposed. Further, all users of
Valcor valves were not notified of the initial problem through either 
oversight by the vendor or as a result of the valves being supplied through 
an intermediate source. 

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:  L. D. Vaughan, IE
                    (301) 492-8811

Attachments: List of Recently Issued IE Information Notices
Page Last Reviewed/Updated Tuesday, November 12, 2013