ML20040C862
| ML20040C862 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 01/20/1982 |
| From: | Parker W DUKE POWER CO. |
| To: | Adensam E, Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| GL-81-21, NUDOCS 8201290322 | |
| Download: ML20040C862 (3) | |
Text
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DUKE POWER COMPANY Powru Ut:storwo
.we SocTu Cnuncu STREET, CHAHLOTTE, N. C. 2824a WILLIAM 0, PAR K FUt, J R.
Sirm PnoovcTsoN -
January 20, 1982
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373-4083 Q
k Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation f
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U. S. Nuclear Regulatory Commission ft>
w J/lf/2 3 gg Washington, D. C.
20555 Z
M #M2mp FC Attention:
Ms. E. G. Adensam, Chief D ecd $g"'lf3 D
Licensing Branch No. 4 g
Re: McGuire Nuclear Station 10 Docket Nos. 50-369 and 50-370 Natural Circulation Cooldown (Generic Letter 81-21)
Dear Mr. Denton:
~
Mr. - D. G. Eisenhut's (NRC/NRR) letter of May 5,1981 (NRC Generic Letter 81--21),
discussed-generic concerns relative to void formation in the vessel head during transients such as that which occurred during the St. Lucie natural circulatica cooldown event of June 11, 1980.
It requested that a review of plant operations
~
be conducted in light of the St. Lucie event. Duke Power Company has completed this review with respect to McGuire Nuclear Station, and implemented the necessary procedures and-training.
In addition, Gen. ic Letter 81-21 requested an assessment of the facility pro-cedures and training program with respect to the matters discussed in the letter.
Three-specific requirements for this assessment were outlined in the letter.
The requested assessment for McGuire Nuclear Station is attached. Should you have any questions concerning the information, please advise.
I declare under penalty of perjury that the statements set forth herein are true and correct to the best of my knowledge.
V ry truly your,
f..,,. g.
William O. Parker, r.
PBN/jfw Attachment Ok
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ATTACHMENT AN ASSESSMENT OF DUKE POWER COMPANY'S MCGUIRE NUCLEAR STATION PROCEDURES AND TRAINING PROGRAM WITH RESPECT TO NRC GENERIC LETTER 81-21 1).
"A demonstration (e.g. analysis and/or test) that controlled natural circulation cooldown from operating conditions to cold shutdown condi-tions, conducted in accordance with your procedure, should not result in reactor vessel voiding."
Response
In June of 1980 a loss of component cooling water to the RC pumps occurred at the St. Lucie Unit 1 nuclear power plant which led to a natural circulation cooldown during which a void formation occurred in the reactor vessel upper head region.
In response to NRC concerns the Westinghouse Owners Group under-took a study with Westinchouse to evaluate the potential for void formation in Westinghouse-designed NSSS's during natural circulation cooldown/depres-surization transients, and to develop appropriate modifications to Westinghouse Owners Group Reference Operating Instruction Guidelines. This study was com-pleted and a summary report sent to the NRC via Owners Group letter OG-57 dated April 20, 1981, R. W. Jurgensen (Chairman, Westinghouse Owners Group) to P. S.
Check (NRC).
The Westinghouse Owners Group Reference Abnormal Operating Instruc-tions were modified to take the results of the study into account so as to pre-clude void formation in the upper head region during natural circulation cooldown/
depressurization transients, and to specify those conditions under which upper head voiding may occur. These Westinghouse Owners Group Generic Guidelines have been submitted to the NRC via Owners Group letter OG-64 dated November 30, 1981, R. W. Jurgensen (Chairman, Westinghouse Owners Group) to D. G. Eisenhut (NRC).
The referenced analysis is applicable to McGuire Nuclear Station, and demon-strates the capability of a Tcold P ant such as McGuire to sustain a natural l
circulation cooldown without void formation in the upper head area.
In addition, McGuire is a UHI plant, making the referenced analysis conservative with respect to McGuire since additional bypass flow is directed into the upper head region.
The generic guidance developed by the Westinghouse Owners Group (augmented as appropriate with plant specific considerations)were utilized in the implemen-tation of McGuire Nuclear Station Operating Procedures.
2).
" Verification that supplies of condensate-grade auxiliary feedwater are sufficient to support your cooldown method".
Response
The condensate-grade sources and maximum capacities for McGuire Nuclear Station are as follows:
Source Maximum Capacity Upper Surge Tanks 85,000 gallons Aux. Feedwater Condensate 42,000 gallons Storage Tanks Condenser Hotwell 170,000 gallons Ictal 297,500 gallons
a A capacity of 240,000 gallons is required to meet the design basis for holding the plant at zero load hot standby conditions for two hours followed by a five hour cooldown to the point where residual heat removal operations are initiated, with a least one reactor coolant pump operating.
The maximum capacity of 297.500 gallons allows sufficient operating margin above the required 240 000 gallons.
3).
"A description of your training program and the provisions of your procedures (e.g. limited cooldown rate, response to rapid change in pressurizer level) that deal with prevention or mitigation of reactor vessel voiding."
Response
The McGuire Nuclear Station Procedure, " Plant Operations during Natural Circulation" contains the following provisions for preventing and/or mitigating reactor vessel voiding:
e All four control rod drive mechanism vent fans are turned on to aid in cooling the head.
The cooldown rate for each loop ia maintained below 50oF/hr.
e This parameter is verified every 30 minutes.
Subcooling in the head is maintained above 15 F.
This para-e meter is verified every 30 minutes.
Operators are cautioned that pressurizer level increases of e
a magnitude greater than charging flow (i.e. rate of rise >
charging flow) indicates a degradation of natural circulation.
The provisions of the above procedures and related industry experience (i.e. St. Lucie event) are covered in both requalification training and license preparatory training.
Establishing and maintaining natural cir-culation is also covered in the simulator portion of license training.