United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 84-64: BWR High-pressure Coolant Injection (HPCI) Initiation Seal-in and Indication

                                                           SSINS No.:  6835 
                                                           IN 84-64        

                               UNITED STATES 
                       NUCLEAR REGULATORY COMMISSION 
                    OFFICE OF INSPECTION AND ENFORCEMENT 
                            WASHINGTON, DC 20555 

                              August 15, 1984 

Information Notice No. 84-64:   BWR HIGH-PRESSURE COOLANT INJECTION 
                                   (HPCI) INITIATION SEAL-IN AND INDICATION 

Addressees: 

All boiling water reactor (BWR) licensees and applicants for an operating 
license. 

Purpose: 

This notice is provided to inform recipients of a potential problem in the 
initiation logic (both automatic and manual) that might prevent the HPCI 
initiation from going to completion. The problem is compounded by erroneous 
system status indication that could be confusing to the operator. This 
potential problem could also exist on the reactor core isolation cooling 
(RCIC) system. It is expected that recipients will review the information 
for applicability to their facilities and take appropriate action. Suggested
actions in this notice do not constitute NRC requirements; therefore, no 
specific action or response is required. 

Description of Circumstances: 

The NRC senior resident inspector at the Shoreham Station discovered that 
the HPCI initiation logic did not go to completion in all cases but did 
cause a status light to come on indicating that the HPCI initiation was 
sealed-in. The problem arose from a combination of two design 
characteristics. First, the HPCI pump discharge valve was interlocked with 
the HPCI turbine steam valves. Second, contacts from the seal-in circuit 
operated the "initiation sealed-in" indicator and operated all the required 
components for HPCI startup, except the HPCI pump discharge valve. 

On automatic actuation, the HPCI pump discharge valve would not start to 
open until both the turbine steam inlet valve and turbine stop valve were no
longer at their fully closed positions and the initiation signal was still 
present. If the initiation signal was not present when the steam valves 
moved off their seats, the pump discharge valve would not open. If the pump 
discharge valve did not open, the HPCI system would not perform its required
safety function and the initiation seal-in circuitry would not satisfy its 
design objective. 

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                                                           IN 84-64       
                                                           August 15, 1984 
                                                           Page 2 of 3    

For manual initiation, a system-level manual pushbutton switch at Shoreham 
was wired in parallel with the low water level relay contacts. The switch 
itself had no mechanical seal-in feature. Therefore, unless the operator 
held the pushbutton for about 12 seconds, which was long enough for the 
turbine steam valves to leave their fully closed positions, the HPCI would 
not inject into the vessel and the HPCI system would come up to an active 
standby mode with the flow being recirculated through the miniflow bypass 
line. Manual operation of the pump discharge valve would then be required to 
achieve injection flow. 

Discussion: 

Besides Shoreham, at least one other late-model BWR-4 design (Hope Creek) 
was known to have a similar design deficiency. Design changes at both 
Shoreham and Hope Creek have provided for a seal-in of the HPCI initiation 
signal. 

In some earlier BWR designs, HPCI manual initiation is provided at the 
component level rather than at the system level. With these designs, the 
manual open switch contact for the pump discharge valve bypasses the 
interlock with the steam valves. Operation of this switch will cause the 
valve to open, but the valve may immediately cycle back to the closed 
position if the steam valves have not yet opened sufficiently to satisfy the
interlock at the time the switch is released. Manual startup of the HPCI 
system in a particular sequence of components may avoid the manual 
initiation problem. 

In many plant designs, both old and new, the system status indication that 
the HPCI logic is sealed-in could be anomalous and unnecessarily generate 
the potential for operator confusion. However, there are other system 
indicators (such as HPCI flow) that do give reliable information regarding 
the status of the HPCI system. 

Licensees and applicants should review their system descriptions, operating 
procedures, and operator training programs to ensure that special 
characteristics of the HPCI and RCIC initiation logics and system status 
indicators are adequately addressed. Appropriate operator awareness may be 
sufficient to allay short-term safety concerns while longer term actions to 
rectify any design deficiencies are being investigated and implemented. 

In particular, if manual initiation of HPCI requires holding a switch for 
several seconds, then licensees may wish to consider appropriate 
precautionary statements in procedures and precautionary labels next to the 
HPCI manual initiation switch. 

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                                                         IN 84-64         
                                                         August 15, 1984  
                                                         Page 3 of 3      

No written response to this information notice is required. If you need 
additional information about this matter, please contact the Regional 
Administrator of the appropriate NRC regional office or the technical 
contacts listed below. 



                                   Edward L. Jordan, Director 
                                   Division of Emergency Preparedness 
                                     and Engineering Response 
                                   Office of Inspection and Enforcement 

Technical Contacts: J. T. Beard, NRR 
                    (301) 492-7465 

                    Eric W. Weiss, IE 
                    (301) 492-4973 

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