ML19351D752
| ML19351D752 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 05/16/1976 |
| From: | Vandenburgh D YANKEE ATOMIC ELECTRIC CO. |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| WYR-76-60, NUDOCS 8011170916 | |
| Download: ML19351D752 (4) | |
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Tel: phon? 617 366-90ll TWX 780-390 0739 YANKEE ATOMIC ELECTRIC COMPANY 20 Turnpoke Road Westborough, Massachusetts 01581
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May 19, 1976 4
h United States Nuclear Regulatory Commission
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maou C09 *llS ON Attention: Office of Nuclear Reactor Regulation M"
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Subject:
Accumulator Pressure Setpoint g
Reference:
(1)
License No. DPR-3 (Docket No. 50-29)
(2) Proposed Change No. 138 (May 11, 1976)
(3) Letter from D. E. Vandenburgh to USNRC (May 11,1976)
(4)
Letter from W. P. Johnson to USNRC (May 17,1976)
Dear Sir:
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Please find attached to this letter supplementary information pertaining to References (2), (3), and (4) above. This information provides a basis for conclusions regarding small LOCA breaks using results of previous analyses.
In addition, Yankee Atomic Electric Company hereby commits to provide to the NRC the results of a confirmatory reanalysis within
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thirty (30) days (i.e. by June 18, 1976). This reanalysis will be performed with the corrected accumulator flow rates as described in Reference (3), and with the accumulator pressure setpoint proposed n '
in Reference (2).
As a minimum, this reanalysis will include:
(a) a reanalysis of the 4-inch pipe rupture previously
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shown to be limiting; j' O '
s (b) an analh.
of a 5-inch pipe and a 10-inch pipe
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rupture, and;
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(c) an analysis of any other size breaks which YAEC 4/.
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most limiting small break size.
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g Respectfully submitted, YANKEE ATOMIC ELECTRIC COMPANY
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D. E. Vandenburgh Vice President AEL/kg
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YANKEE ROWE-
~SMALL BREAK ANALYSES 1.
ANALYSES AVAILABLE FOR EXAMINATION P.C..#125 P.C. #117 P.C. #96 Supp. #1' 7/31/74 8/6/71 10/10/76 (WFLASH)
(SLAP)
(WREM) 3-inch pipe
(.0376 it.2)
NO YES YES 4-inch-pipe YES YES NO
'5-inchpipe
'(.101 ft. )
NO NO YES 2.
HIGHLIGHTS OF EXAMINATION (a) The three models produc'ed consistent blowdown and refill trends for the cases in common, i.e.
- 1) 4-inch WREM = 4-inch WFLASH ii) 3-inch WFLASH = 3-inch SLAP (b) Trends in depressurization and refill rates were consistent for the three' break sizes considered, i.e.
Blowdown Rate for 5-inch pipe 1 Blowdown rate for 4-inch pipe 1 Blowdown rate for-3-inch pipe.
(c) Increased blowdown rates for larger breaks > 4" allowed the ECCS system to inject into RCS sooner and thus reflood sooner.
This trend would~
cause the smaller breaks to be more limiting.
(d) Howevar, for breaks smaller than 4" pipes (size of ECCS penetration into RCS), credit for no direct spillage of SI fluid produced more effective ECCS performance resulting in.the limiting break being no less than the 4" pipe..
(e) So the PCT versus break size looked-like:
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PCT l l 1
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x 0d f ( 1.0 x DECLG break 4-inch pipe
.6 x DECLG (f) Impact of reduced accumulator pressure was felt in the smallest break in which it played a role in terminating the transient, i.e. 4" pipe.
This is because smaller breaks produce slower blowdown rates thus yielding the greatest delay in onset of accumulator delivery to RCS.
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.NR,C DISTRIDUTION ran PART 50 DOCKET MATERIAL 10:
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DATC OF DOCutAC Nr M. (
Yankce AEo. tic Elec C 5-1"-7t'
' cstborongh, Itass DATE nECC4VCD D E Vandenburgh 5-22-76 Mttircn
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Proposed Changc.
Ltr rt their 5-17-7e 1er....trans the follow:
Supplerental info pertaing tv 1139 ctd 5-11-7n unice concarus basis for coiclusicas reprding srall LOCA brcus usin~
rccults cf previous inalysis..................
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