W3P82-2340, Discusses Discrepancy Between as-built Core Protection Calculator Software & C-E Functional Requirements,Identified in Phase II Test Rept.Current Operation of Calculators Using Present Software Acceptable.Qa Analysis Expected in Sept

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Discusses Discrepancy Between as-built Core Protection Calculator Software & C-E Functional Requirements,Identified in Phase II Test Rept.Current Operation of Calculators Using Present Software Acceptable.Qa Analysis Expected in Sept
ML20063L741
Person / Time
Site: Waterford Entergy icon.png
Issue date: 09/03/1982
From: Maurin L
LOUISIANA POWER & LIGHT CO.
To: Tedesco R
Office of Nuclear Reactor Regulation
References
W3P82-2340, NUDOCS 8209090208
Download: ML20063L741 (3)


Text

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142 DELARONDE STRFET POWER & LlGHT P O BOX 6008 . NEW ORLEANS. LOUISIANA 70174 . [504) 366 2345 MIDCLE SOUTH unUT:LS S(STEM September 3, 1982 t,y, uavafu Vice President Nuclear Operations l

W3P82-2340 1 3-A1.01.04 Q-3-C31.02 Mr. R. L. Tedesco Asst. Director of Licensing U. S. Nuclear Regulatory Commission Washington, D. C. 20555

SUBJECT:

Waterford Steam Electric Stacion - Unit No. 3 Docket No. 50-382 CPC Software Functional Inconsistency

Dear Sir:

Recent qualification testing of the WSES-3 Core Protection Calculator (CPC) software has revealed a discrepancy between the "as-built" software and C-E's functional requirements. This has been identified in the Phase II Test Report [CEN-208 (C)] which was recently submitted to the NRC.

The discrepancy involves penalty factors associated with failed Control Element Assembly Calculators (CEACs) . When both CEACs are " failed", the functional requirements specify that the CPCs are to use DNBR and LPD pen-alty factors (PFs) stored in the CPC data base. These PFs are the largest possible PFs that the CEACs could calculate during normal operation. In addition, the PFs are to be used with one CEAC " failed" and the other is "RSPT/CEAC INOP". A CEAC is considered " failed" by the CPCs whenever the FAlLED BIT is set on the data link from the CEAC to the CPCs. This FAILED BIT is set by the CEAC whenever the CEAC determines that it has a detect-able failure or is placed in " test". Recent testing of the CPC software on another plant has revealed that, during the above conditions, the large DNBR PF is applied but the large LPD PF h not. We believe that no safety concern exists for the following reasons.

For most plant operating conditions, the plant will immediately trip on failure of both CEACs due to the application of the large DNBR PF. The absence of the large LPD PF is therefore moot. There is a small set of plant conditions, notably at low power, under which the plant may not trip immediately. Based on current evaluations, C-E has determined that no de-sign basis CEA misoperation event initiated from these initial conditions f will result in exceeding Specified Acceptable Fuel Design Limits. The con-clusions of the plant safety analyses presented in Chapter 15 therefore re-main valid. Therefore, it can be concluded that the LPD trip function is not required for plant protection under these conditions.

8209090209 820903 DR ADOCK 05000382 PDR l

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Mr. R. L. Tedesco W3P82-2340 (

Page Two In addition, it has been determined that the probability of achieving this very specific set of plant conditions is exceedingly small because: (1)

The probability of a failure of both CEACs (or the failure of a single CEAC with the other in the "RSPT/CEAC INOP" Mode) is very small; and (2) Technical Specifications specifically do not allow continued operation under these con--

ditions; (3) the probability of a CEA misoperation event (the only design basis event which could approach the LPD SAFDL) occurring when in this mode is also very small. It should be stressed that when only one CEAC is " failed",

or when one or both CEACs are in the "RSPT/CEAC INOP" Mode, the CPCs function as intended.

r Based on the above, it has been concluded that current operation of the CPCs using the present software is acceptable. A quality assured analysis to do-r cument the acceptability of the present software is currently being performed.

This is expected to be completed in September, 1982, at which time you will be notified.

1 L. V. Maurin LVM/RMF/snw cc: E. L. Blake, W. M..Stevenson, S. Black I

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  • 4 bec: Ebasco (2), J. M. Brooks, R. J. Milhiser (2), F. J. Drummond, T. F. Gerrets, C. J. Decareaux, T. K. Armington, P. V. Prasankumar, J. R. McGaha, J. F. Fager, Richard Hymes, L. L. Bass, M. I. Meyer, R. W. Prados, K. R. lyengar, J. J. Lewis, L. V. Maurin, G. B. Rogers, R. M. Wilkins, J. R. Trinko, Central Records, Nuclear Records (3),

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