United States Nuclear Regulatory Commission - Protecting People and the Environment


LICENSEE: SIEMENS POWER CORP/NUCLEAR DIVISION

SITE: SIEMENS POWER CORP/NUCLEAR DIV        EN NUMBER:34162

DOCKET:                                  EVENT DATE: 04-29-98

RX TYPE:                                 EVENT TIME: 17:00

VENDORS:                                NOTIFY DATE: 05-01-98

EMERGENCY CLASS: N/A  REGION: 4 STATE: WA      TIME: 11:20

OPS OFFICER: DICK JOLLIFFE            

10 CFR SECTION: CCCC  21.21               UNSPECIFIED PARAGRAPH



10 CFR PART 21 REPORT - DEVIATION IN THE RELAP4 PORTION OF THE   

LARGE BREAK LOSS OF COOLANT ACCIDENT (LBLOCA) EVALUATION MODEL   

(REFER TO EVENT #34165 FOR ADDITIONAL INFORMATION.)              

                                                                 

SIEMENS POWER CORPORATION (SPC) HAS IDENTIFIED A DEVIATION IN THE

RELAP4 PORTION OF THE LBLOCA EVALUATION MODEL.  SMALL CHANGES IN 

THE INPUT TO RELAP4 (PART OF THE EXEM/PWR LBLOCA EVALUATION      

MODEL) CAN RESULT IN LARGE CHANGES IN THE CALCULATED PEAK        

CLADDING TEMPERATURE DURING A LBLOCA.  THESE RESULTS ARE         

CONSIDERED EXCESSIVE GIVEN THE SIZE OF THE INPUT CHANGES.  THE   

PLANTS FOR WHICH SPC PROVIDES LBLOCA ANALYSES HAVE ALL BEEN      

EVALUATED WITH THIS DEVIATION CORRECTED IN THE LBLOCA EVALUATION 

MODEL.  THE RESULTS OF THESE ANALYSES FOR FOUR OF THESE PLANTS   

INDICATE THAT THE EARLIER ANALYSES WITH THE DEVIATION ARE        

CONSERVATIVE [i.e., RESULT IN HIGHER PEAK CLADDING TEMPERATURES  

(PCT)] RELATIVE TO THE RESULTS FROM THE CORRECTED MODEL.  THE    

PCTs ARE LOWER USING THE CORRECTED MODEL FOR THESE FOUR PLANTS BY

APPROXIMATELY 30�F TO 130�F.                                     

                                                                 

THE RESULTS OF THE ANALYSES FOR A FIFTH PLANT, MILLSTONE UNIT 2, 

INCREASE THE PCT BY MORE THAN 50�F, AND THE PCTs EXCEED THE      

2,200�F CRITERION IN                                             

10 CFR 50.46.  MILLSTONE UNIT 2 IS CURRENTLY SHUTDOWN AND        

DEFUELED.  A REVISED LBLOCA ANALYSIS TO SUPPORT THE RESTART OF   

MILLSTONE UNIT 2 WILL BE PROVIDED BY SPC TO NORTHEAST UTILITIES. 



LICENSEE: NORTHEAST UTILITIES                

SITE: MILLSTONE 2                           EN NUMBER:34165

DOCKET:  05000336                        EVENT DATE: 05-01-98

RX TYPE:  PWR                            EVENT TIME: 15:00

VENDORS:  CE                            NOTIFY DATE: 05-01-98

EMERGENCY CLASS: N/A  REGION: 1 STATE: CT      TIME: 15:27

OPS OFFICER: CHAUNCEY GOULD           

10 CFR SECTION: AINC  50.72(b)(2)(iii)(C) POT UNCNTRL RAD REL  

UNIT  SCRAM   RX   INIT  INITIAL MODE     CURR   CURRENT MODE

      CODE   CRIT  PWR                    PWR

 2    N       N      0   REFUELING          0   REFUELING      



POSSIBILITY OF THE REACTOR EXCEEDING ITS PEAK CLAD TEMPERATURE   

LIMIT (REFER TO EVENT #34162 FOR ADDITIONAL INFORMATION.)        

                                                                 

THE LICENSEE WAS INFORMED BY THE FUEL VENDOR (SIEMENS POWER      

CORPORATION) THAT A PRELIMINARY REANALYSIS FOR THE LARGE BREAK   

LOCA INDICATES THAT                                              

UNIT 2 WOULD EXCEED A PEAK CLAD TEMPERATURE OF 2,200�F DURING THE

WORST CASE ANALYZED LARGE BREAK LOCA.  THIS IS IN VIOLATION OF   

THE CRITERIA CONTAINED IN 10 CFR 50.46 AND GENERAL DESIGN        

CRITERION 35.  THE REVISED ANALYSIS INDICATES THAT PEAK CLAD     

TEMPERATURE WOULD ONLY EXCEED 2,200�F IF THE LINEAR HEAT RATE IS 

GREATER THAN 14.6 KW/FT AT THE START OF THE LARGE BREAK LOCA     

EVENT.  UNIT 2 TECHNICAL SPECIFICATIONS ALLOW OPERATION WITH A   

LINEAR HEAT RATE AS HIGH AS 15.1 KW/FT.  THE LARGE BREAK LOCA    

EVENT IS IN THE PROCESS OF BEING REANALYZED.                     

                                                                 

THE NRC RESIDENT INSPECTOR HAS BEEN NOTIFIED BY THE LICENSEE.    





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