United States Nuclear Regulatory Commission - Protecting People and the Environment

Resolution of Generic Issue 69: High Pressure Injection/Make-up Nozzle Cracking in Babcock and Wilcox Plants (Generic Letter No. 85-20)



                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                           WASHINGTON, D. C. 20555

                              November 8, 1985

TO ALL LICENSEES WITH BABCOCK AND WILCOX OPERATING REACTORS 

Gentlemen: 

SUBJECT:  RESOLUTION OF GENERIC ISSUE 69: HIGH PRESSURE INJECTION/MAKE-UP 
          NOZZLE CRACKING IN BABCOCK AND WILCOX PLANTS (Generic Letter 
          85-20) 

On January 24, 1982, an unexplained loss of coolant was detected during 
normal plant operation at Crystal River Unit 3. After an orderly shutdown, 
an inspection of the reactor coolant and associated systems revealed that 
the high pressure injection/makeup (HPI/MU) check valve, valve-to-safe-end 
weld, safe-end, and the mal sleeve were cracked. Subsequently, inspections 
were performed at other B&W designed plants. Most of these inspections 
revealed similar types of cracking in the HPI system of the facilities which 
indicated that the cracking problem was a generic one. A Safe-End Task Force 
was formed by the B&W Owners' Group to compile pertinent facts and to make 
recommendations to solve the cracking problem. The Task Force completed its 
work in late 1982 and provided its findings and recommendations to the 
Owners' Group in the "Babcock and Wilcox 177 Fuel Assembly Owners' Group 
Safe-End Task Force Report on Generic Investigation of HPI/MU Nozzle 
Component Cracking." 

The staff reviewed the Task Force recommendations and agreed that the 
following actions be taken to resolve this issue: 

(1)  Reroll the upstream end of the thermal sleeve when inspections indicate
     that a gap exists or repair and/or replace damaged components; 

(2)  Implement an augmented inservice inspection plan; and 

(3)  Perform a detailed stress analysis of a nozzle with a modified thermal 
     sleeve design to justify long term operation. 

All participants in the Owners' Group Task Force have performed the 
recommended repairs to damaged components (Recommendation 1) and have 
voluntarily implemented a satisfactory augmented inservice inspection 
program (Recommendation 2). Performance of a stress analysis (Recommendation 
3) is required to maintain original licensing commitments regarding the 
stress and fatigue usage allowables required by USAS B31.7 or the ASME code. 
Analyses for modified nozzles have been performed; analyses for nozzles not 
requiring modification should have been performed before licensing. 
Operating experience for some plants has indicated that the expected fatigue 
analyses could be substantially exceeded by the end of life. For example, an 
increased number of HPI actuation transients could occur due to manual 
actuation after reactor trips to avoid losing pressurizer level. Therefore, 
the staff has determined that it is necessary to ensure that valid stress 
analyses have been performed. 


8511050057  

                                                           November 8, 1985 

                                     - 2 - 

Each licensee should verify that a valid stress analysis has been performed 
for HPI/MU nozzles in accordance with its licensing commitments to meet the 
Code requirements. Also, each licensee should verify that the cumulative 
fatigue usage for these nozzles is within the allowables based on a 
realistic projection of the thermal cycles expected for the life of the 
plant. The information including stress analysis results and expected number 
of thermal cycles should be maintained for future inspection. 

This generic letter does not impose any new regulatory requirements or any 
reporting requirements. Therefore, no clearance from the Office of 
Management and Budget is required. If you have any questions, the staff 
contact John Hannon who can be reached at (301) 492-8543. 


                              Hugh L. Thompson, Jr., Director 
                              Division of Licensing 

cc: List of Generic Letters 
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