United States Nuclear Regulatory Commission - Protecting People and the Environment

Bulletin 80-18: Maintenance of Adequate Minimum Flow Thru Centrifugal Charging Pumps Following Secondary Side High Energy Line Rupture

                                                            SSINS No.: 6820 
                                                            Accession No.:

                                UNITED STATES
                           WASHINGTON, D.C. 20555

                                July 24, 1980

                                                      IE Bulletin No. 80-18 


Description of Circumstances: 

Letters similar to the May 8, 1980 notification made pursuant to Title 10 
CFR Part 21 (enclosure) were sent from Westinghouse to a number of operating
plants and plants under construction (list, within enclosure) in early  May,

The letters and the enclosed "Part 21" letter contain a complete description
of the potential problem summarized below. The letters indicated that under 
certain conditions the centrifugal charging pumps (CCPs) could be damaged 
due to lack of minimum flow before presently applicable safety injection 
(SI) termination criteria are met. The particular circumstances that could 
result in damage vary somewhat from plant to plant, but involve 
unavailability of the pressurizer power operated relief valves (PORVs), with 
operation of one or more CCPs repressurizing the reactor during SI following 
a secondary system high energy line break. Since the SI signal automatically 
isolates the CCP mini-flow return line, the flow through the CCPs is 
determined by the individual pump characteristic head vs. flow curve, the 
pressurizer safety valve setpoint, and the flow resistances and pressure 
losses in the piping and in the reactor core. That minimum flow may not be 
adequate to insure pump cooling, and resulting pump damage could violate 
design criteria before current SI termination criteria are met. 

Westinghouse recommends that plant specific calculations outlined in the 
letter (enclosure) be performed to determine if adequate minimum flow is 
assured under all conditions. If adequate minimum flow is not assured, 
Westinghouse recommends specific equipment and procedure modifications which
will result in adequate minimum flow. The recommended modifications assure 
availability of the necessary minimum flow by assuring that the mini-flow 
bypass line will be open when needed, but will be closed at lower pressures 
when the extra flow resulting from bypass line closure might be necessary 
for core cooling. 

IE Bulletin No. 80-18                                      July 24, 1980 
                                                            Page 2 of 3 

Actions to be taken by PWR licensees listed in the enclosure as "operating 
plants," and those listed as "non-operating plants" which are nearing 
licensing* are listed below: 

1.   Perform the calculations, outlined in the enclosure, for your plant. 

2.   If availability of minimum cooling flow for the CCPs is not assured for
     all conditions by the calculations in 1: 

     a.   Make modifications to equipment and/or procedures, such as those 
          suggested in the enclosure, to insure availability of adequate 
          minimum flow under all conditions. If modifications are made as 
          described in the attachment for interim modification II, verify 
          that the Volume Control Tank Relief Valve is operable and will 
          actuate at its design setpoint. 

     b.   Justify that any manual actions necessary to assure adequate 
          minimum flow for any transient or accident requiring SI can and 
          will be accomplished in the time necessary. 

     c.   Verify that any manipulations required (valve opening or closing, 
          along with the instrumentation necessary to indicate need for the 
          action or accomplishment of the action, etc.) can be accomplished 
          without offsite power available. 

     d.   Justify that flow available from the CCPs with the modifications 
          in place will be sufficient to justify continued applicability of 
          any safety related analyses which take credit for flow from the 
          CCPs (LOCA, HELB, etc.). 

     e.   Justify that all Technical Specifications based on the Item 2.d 
          analyses remain valid. 

     3.   Provide the results of calculations performed under Item 1, and 
          describe any modifications made as a result of Item 2 (include the
          justifications requested). 

Actions to be taken by PWR licensees not listed in the enclosure are listed 

1.   In a quantitative manner similar to 1 above, determine whether or not 
     minimum cooling is provided to centrifugal pumps used for high pressure
     injection, for all conditions requiring SI, prior to satisfying SI 

*    Those listed in the enclosure considered to be "nearing licensing" are:
     North Anna 2, Diablo Canyon 1, McGuire 1, Salem 2, and Sequoyah. These 
     plants must respond in writing within the specified time. Other 
     non-licensed plants whether or not listed in the enclosure, are not 
     required to submit a written response at this time. 

IE Bulletin No. 80-18                                      July 24, 1980 
                                                            Page 3 of 3 

termination criteria. If a "minimum flow bypass" line is present which 
remains open during high pressure injection, and if that line guarantees 
that minimum cooling flow will be provided to the pumps under such 
conditions, then no further calculations are required if all safety related 
analyses (Item 2.d above) assumed presence of the open line. 

2.   Same as 2 above. 

3.   Same as 3 above. 

Licensees of all operating PWR power reactor facilities and those nearing 
licensing* shall submit the information requested within 60 days of the date
of this letter. Include in your response to this Bulletin, (a) your schedule
for any changes proposed, (b) if reactor operation is to continue prior to 
completion of the proposed changes, include your justification for continued

Reports shall be submitted to the Director of the appropriate NRC Regional 
Office and a copy forwarded to the Director, NRC Office of Inspection and 
Enforcement, Division of Reactor Operations Inspection, Washington, D.C. 

Approved by GAO, B280225 (R0072); clearance expires 7-31-80. Approval was 
given under a blanket clearance specifically for identified generic 

Ltr from T. M. Anderson, W 
to V. Stello, IE dtd 5/8/80

*Those considered to be "nearing licensing" are: North Anna 2, Diablo Canyon
1, McGuire, Salem 2, and Sequoyah. 
Page Last Reviewed/Updated Friday, May 22, 2015