United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 86-50: Inadequate Testing to Detect Failures of Safety-Related Pneumatic Components or Systems

                                                         SSINS No.:  6835  
                                                         IN 86-50          

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

                                June 18, 1986

Information Notice No. 86-50:   INADEQUATE TESTING TO DETECT FAILURES OF 
                                   SAFETY-RELATED PNEUMATIC COMPONENTS OR 
                                   SYSTEMS 

Addressees: 

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

Purpose: 

This notice is being provided to alert recipients to a potentially 
significant problem pertaining to inadequate testing practice relating to 
air operated valves. The NRC expects that recipients will review this notice 
for applicability to their facilities. However, suggestions contained in 
this notice do not constitute NRC requirements; therefore, no specific 
action or written response is required. 

Past Related Correspondence: 

Information Notice No. 82-25, "Failures of Miller Actuators Upon 
  Gradual Loss of Air Pressure," July 20, 1982 

Information Notice No. 85-35, "Failure of Air Check Valves to Seat," 
  April 30, 1985 

Information Notice No. 85-84, "Inadequate Inservice Testing of Main 
  Steam Isolation Valves," October 30, 1985 

Information Notice No. 85-94, "Potential for Loss of Minimum Flow 
  Paths Leading to ECCS Pump Damage During a LOCA," December 13, 1985 

Description of Circumstances: 

The NRC has reported previously on instances where safety-related equipment 
failed to operate as intended when non-safety-related pneumatic systems were
unavailable (IE INs 82-25 and 85-35). In these situations, main steam 
isolation valves and containment isolation valves failed to operate properly
when control air pressure decreased slowly rather than rapidly as would be 
expected for an air line break. In the case of IN 85-35, the fault was 
exposed by a loss of offsite power test, and in the case of IN 82-25, the 
fault was exposed by a preoperational test designed to simulate a slow air 
leak. In both cases,  



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                                                            IN 86-50
                                                            June 18, 1986  
                                                            Page 2 of 3 

the components in question--an accumulator isolation check valve (IN 85-35) 
and pneumatic selector valves (IN 82-25)--were not tested adequately. 
Several recent events have indicated continuing problems of similar nature. 
These events are discussed below. 

On February 13, 1986, the licensee at Turkey Point Unit 3 first reported to 
the NRC a concern that the component cooling water (CCW) system might fail 
to meet its functional requirements for a design-basis accident. One part of
the concern involved the CCW heat exchanger outlet control valve. This valve
regulates flow of intake cooling water (ICW) to this heat exchanger. Loss of
control air, coincident with a loss of offsite power, a valid engineered 
safeguards features (ESF) actuation signal, and a loss of an emergency 
diesel generator (EDG) would cause this valve to fail closed. If this 
happened, the CCW heat exchanger would not receive sufficient flow of ICW. 
This situation was discovered during a design review of the ICW system. 
Earlier disclosure might have been possible if ICW operation had been 
considered or tested with non-safety-related control air secured, coincident 
with loss of electrical power. 

On January 7, 1986, the licensee at Robinson Unit 2 reported a concern with 
the air-operated valves in the safety injection (SI) pump minimum-flow 
recirculation line from the pump discharge to the refueling water storage 
tank (RWST). This concern evolved from review of IN 85-94. Two such valves 
had been inserted in series in this line and had been designed to fail 
closed on loss of non-safety-related air or loss of electrical power to the 
valves. The purpose of the valves is to protect the RWST (outside 
containment) from highly radioactive reactor coolant during the long-term 
circulation phase of accident recovery. In the event of SI initiation under 
small-break loss-of-coolant-accident conditions concurrent with closure of 
either of these valves, the SI pumps would be operating with no flow until 
reactor pressure decreased below their shutoff head. This would damage the 
SI pumps after only a short time. The licensee's remedy was to put 
mechanical blocks on the air operators so the valves would fail as-is 
(open). Again, if SI operation had been considered or tested with 
non-safety-related control air secured, the fault might have been disclosed 
earlier. 

On December 9, 1985, the licensee at Catawba Unit 2 reported finding that 
one of the two valve closure springs was missing on one of the pressurizer 
power-operated relief valves (PORVs). Thus, with loss of air the valve would
not have closed against system pressure. The other two PORVs had their 
normal complement of springs. The valve with the missing spring had been 
found satisfactory in preoperational tests. During the preoperational loss 
of air test, the valve closed because system pressure was not present; 
during the hot functional test, the valve closed because actuator air 
pressure was present. This is clearly a case in which a fail safe valve was 
tested without all actuator power secured (IN 85-84). 

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                                                            IN 86-50  
                                                            June 18, 1986  
                                                            Page 3 of 3 


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:  Vern Hodge, IE 
                    (301) 492-7275 

Attachment:    List of Recently Issued IE Information Notices 

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