ML20195D828
| ML20195D828 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood, 05000000 |
| Issue date: | 11/02/1988 |
| From: | Chrzanowski R COMMONWEALTH EDISON CO. |
| To: | Murley T Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8811070143 | |
| Download: ML20195D828 (3) | |
Text
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T'N Commonwealth Edloon
) One First National Plata Chic *go, filinojs j Addr:ss R ply to: Post Offics Bos 767 O
Chicago, Ithnois 60690 y
November 2, 1988 Mr. Thomas E. Murley, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555 Subject Byron Station Units 1 and 2 Braidwood Station Units 1 and 2 Natural Circulation Capacity MRC A cket Nos. 50-41(/455 and 50-456/457 Refero.tces (a) October 14, 1988, letter from R. A. Chrsanowski to T. E. Murley
Dear Mr. Murley:
In Reference (a), Commonwealth Edison responded to a request for additional information that was received f rom the NRC.
Attachment A to this letter provides.further information to answer NRC follow-up questions regarding the comparison between Byron /Braidwood and Diablo Canyon. This comparison will show that the Diablo Canyon natural circulation prototest results will be representative of the natural circulation and boron mixing capability of Byron /Braidwood.
Please direct any further questions regarding this matter to this office.
Very truly yours, h0$nusta)
R. A. Chrsanowski Nuclear Licensing Administrator cet Byron Resident Inspector Braidwood Resident Inspector S. Sands (NRR)
D. Katse (NRR)
Region III Office 5285K Af
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ATTACittDIT A 1
Subjects Natural Circulation Cooldown Comparison Between Byron /Braidwood and Diablo Canyon t
After further conversations with Westinghouse, the following information has been verified.
Due to the T-cold design at Byron /Braidwood, spray nossles between the down comer and upper head areas exist.
Furthermore, these nossles permit better communication and mixing between the upper head and down comer regions during natural circulation conditions than at T-hot plants, such as Diablo Canyon.
- The steam generator design comparison between the Diablo Canyon, Model 51's and the Byron /Braldwood Model D4/D5's showed that the thermal driving head during natural circulation conditions would be greater for the D4/D5 steam generators than that of the Model 51's.
In addition, a similar comparison between the Millstone Model r steam generators and the Byron /Braidwood Model D4/D5's was completed that showed the Byron /Braldwood thermal driving head equal to or slightly greater than that at Millstone.
The following information is provided to clarify the previous response.
The Byron /Braldwood Stations require 2 steam generator atmospheric relief valves be available for cooldown during a steam generator tube rupture event coincident with natural circulation conditions, as described in the "Steam Generator Tube Rupture Analysis for the Byron and Braldwood Plants" dated August, 1988.
The Byron /Braldwood Stations have the following water sources available for cooldown.
1)
M ate r_S antcan_fo r._the_ Aux ilia ry_Le eh ate r_fump s
- The condensate Storage Tasks
- capacity 500,000 gallons
- normal ops 300,000 gallons
- required 200,000 gallons
- The essential service water cooling towers basins for Byron Station
- normal ops 500,000 gallons
- required 290,000 gallons
4
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- The essential service water cooling pond for Braidwood Station has a water inventory in excess of several million gallons.
f 2)
The water source for a primary "bleed" through the pressuriser PORV's and a "feed" from the refueling water storage tank (RWST) through the hi-head safety injection flow path is available. The water volume ist RNST. capacity 450,000 gallons required 390,000 gallons The pressuriser PORV's are environmentally qualified. Therefore, even through the PRT is designed to absorb a discharge of steam equivalent to 110% of the full power pressurisation steam volume without rupture, if the PRT rupture disk were to rupture and cause the containment to reach an environmentally harsh condition, the PORV's are designed to operate prope rly. Additionally, the pressuelser PORVs are designed with safety related air accumulators that ensure each PORV can cycle at least 50 times, which is more than adequate to permit cooldown and depressurisation during nature circulation conditions.
The 2 pressuriser PORV's are capable of being isolated in the event that either PORV fails open or does not fully close after it is opened for cooldown or depressurisation by utilising it's associated block valve.
There is a safety related block valve upstream of each of the 2 PORV's.
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