ML20137Q440
| ML20137Q440 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 11/26/1985 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | Butcher E, Harold Denton NRC, Office of Nuclear Reactor Regulation |
| References | |
| 85-801, NUDOCS 8512050273 | |
| Download: ML20137Q440 (2) | |
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VIHOINIA ELECTR?C AND Pownx COMPANY HIcnwoNn, VIRGINIA 20261 W.L.Stawant vic. r..... 1 November 26, 1985 Noct.A. Dr..ATiON.
Mr. Harold R. Denton, Director Serial No.85-801 Office of Nuclear Reactor Regulation N0/DJV:acm Attn: Mr. Edward J. Butcher, Acting Chief Docket Nos. 50-338 Operating Reactors Branch No. 3 50-339 Division of Licensing License Nos. NPF-4 U.S. Nuclear Regulatory Commission NPF-7 Washington, D.C. 20555 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS NO. 1 AND 2 LOCKED ROTOR ACCIDENT ANALYSIS-REQUEST FOR ADDITIONAL INFORMATION Our letter of February 7, 1985 (Serial No. 666) presented an analysis of the postulated locked rotor accident for North Anna Units No. I and 2.
On November 14, 1985, in a telephone conference with the NRC staff regarding this submittal, Ms. Margaret Chatterton of your staff requested that we provide the percentage of fuel rods in the core which are predicted to experience a Departure from Nucleate Boiling Ratio (DNBR) of less than 1.30 during the locked rotor accident. The purpose of this letter is to provide our response to that request.
Using the transient results (heat flux, flow rates, etc.) presented in our February 7 submittal as forcing functions, a detailed core thermal-hydraulic analysis was performed using the COBRA III C/MIT Code.
The results of this analysis were used in conjunction with the calculated core power distributions for severn1 recent North Anna reloads to calculate the maximum percentage of fuel rods which would experience a W-3 minimum DNBR of less than 1.30 during the locked rotor accident. The results showed that less than 2% of the fuel rods would experience a DNBR of less than 1.30 (i.e. at a 95% confidence level, no more than 2% of the rods would have a DNB probability exceeding 0.05) during this event.
Future reload cores will be reviewed to verify that.this conclusion remains valid.
Very truly yours,
\\
Lk W. L. Stewart 8512050273 85112 ADOCK 05%338 00 PDR R
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r-a; VinoMu ELucralC AMD Powna COMPANY TO Mr, ((arOld R. Denton cc:
Dr. J. Nelson Grace Regional Administrator
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NRC Region II Mr. Morris W. Branch NRC Resident Inspector North Anna Power Station Mr. Leon B. Engle NRC North Anna Project-Manager Operating Reactors Branch No. 3 Division of. Licensing e-