United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 86-82: Failures of Scram Discharge Volume Vent and Drain Valves

                                                            SSINS No.: 6835 
                                                            IN 86-82 
                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF INSPECTION AND ENFORCEMENT
                           WASHINGTON, D.C. 20555

                             September 16, 1986

Information Notice No. 86-82:   FAILURES OF SCRAM DISCHARGE VOLUME VENT 
                                   AND DRAIN VALVES 

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 
problem pertaining to failures of the Hammel-Dahl valves used as vent and 
drain valves in the control rod drive (CRD) systems of certain boiling water
reactors. It is suggested that recipients will review the information for 
applicability to their facilities and consider actions, if appropriate, to 
preclude a similar problem from occurring at their facilities. However, 
suggestions contained in this information notice do not constitute NRC 
requirements; therefore, no specific action or written response is required.

Description of Circumstances: 

On February 8, 1985, the General Electric Company (GE) notified the NRC of a 
coupling failure of the 2"-2500# Hammel-Dahl valve used as a CRD drain valve 
in the scram discharge volume (SDV). The coupling connected the air actuator 
to the valve stem and its failure prevented the valve from fully opening or 
closing. This failure had occurred during equipment qualification in a 
laboratory and was due to automatic actuation while the manual handwheel was 
partially engaged. 

GE identified the 2"-600#, 1"-2500#, and 1"-600# as having the same coupling
design. The 1" valves are used as SDV vent valves. 

On May 13,1985, GE issued service information letter (SIL) 422 to inform its
customers of the potential for failure of the valve and recommended actions.
In SIL 422, GE mentions a related problem that occurred at an operating 
plant. Subsequently, two additional operating plants have experienced valve 
failures caused by partially engaged handwheels: Limerick in November of 
1985 and Hope Creek in May of 1986. Limerick found an SDV drain valve with 
its handwheel off the neutral position and attempted to actuate the valve 
from the control room. The valve would not operate. Hope Creek found a 
coupling failed in a drain valve and the handwheel partially engaged. 



8607110321 
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                                                       IN 86-82          
                                                       September 16, 1986 
                                                       Page 2 of 2       

Discussion: 

The SDV vent and drain valves are primary containment isolation valves that 
are normally open while the plant is operating. There are two valves in 
series in each vent and drain line. They allow water from the normal CRD 
seal leakage to drain to radwaste rather than accumulate in the SDV. When a 
scram occurs, the vent and drain valves close to isolate reactor coolant 
from radwaste. 

GE SIL 422 recommends that licensees "provide adequate training, operating 
procedures, and checks to help assure that the handwheels of the valves are 
in the neutral position to prevent inadvertent engagement of the handwheel 
during automatic actuation of the valves. 

When the handwheel is engaged or partially engaged, the automatic actuation 
function may be prevented, or, if it occurs, may damage the actuator or stem
of the valve, causing it to fail in its "as-is" position. These valves are 
primary containment isolation valves. If two valves in series fail open, a 
discharge path will exist for reactor coolant to drain to the plant drain 
system. This path can be isolated by resetting the scram signal or by 
manually closing the #102 or #112 valves on each associated hydraulic 
control unit (HCU). (There are approximately 92 HCUs per SDV.) If the vent 
and drain valves fail closed, the CRD seal leakage will collect in the SDV 
until the SDV level reaches the scram set point. 

The failure of either redundant vent valve and or either redundant drain 
valve represent a degradation of safety systems (CRD, primary containment, 
and the primary containment isolation system) and could result in 
unnecessary challenges of the reactor protection system. Licensee corrective 
actions have included training, procedure revision, and enhanced 
surveillance as well as adding administrative controls to maintain the 
handwheels in the neutral position. 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:  Mary S. Wegner, IE
                    (301) 492-4511

Attachment: List of Recently Issued IE Information Notices
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