ML19270F326
| ML19270F326 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 02/01/1979 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| TAC-49501, NUDOCS 7902060258 | |
| Download: ML19270F326 (3) | |
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@' SMUD SACRAMENTO MUNICIPAL UTILITY DISTRICT O 6201 S street, Box 15830, Sacramento, California 95813; (916) 452-3211 February 1,1979 Director of Nuclear Reactor Regulation Attn:
Rober ' W. Reid, Chief Operat 'ng Reactors, Branch No. 4 U. S. Nuclear Regulatory Commission Washington, D. C.
20555 Docket No. 50-312 Rancho Seco Nuclear Generating Station, Unit No. 1
Dear Mr. Reid:
Your letter of December 26, 1978 requests certain information regarding our proposed modification for storing the reactor cavity seal plate during reactor operation.
The attached sketch shows the proposed modi fication.
The following design criteria were considered to arrive at this concept:
1.
The structure will be designed to restrain the seal plate under a combination of seismic and LOCA loads.
2.
The structure will be designed so service structure stresses will stay within allowable limits.
3.
The structure will be designed to pennit movement of the stud tensioners and in-service inspection equipment with the existing chain hoists.
4.
The structure will be designed to allow a maximum of shop fabrication to reduce radiation exposures during installation.
The total estimated cost of this modification is $92,000; consisting of $57,000 for analysis and engineering, $15,000 for materials and $20,000 for installation. This cost represents the total cost of the modification if it is installed at the next refueling outage.
It is further estimated that at least a nine day outage would be required to install this modification if the plant were shut down for this purpose.
This includes time for cooldown, missile shield removal and re-installation, scaffold setup and removal, installation, and return to power.
During this period replacement power would be from oil fired generation which costs an additional 20 mills per KWH, resulting in an outage cost of almost $4 million.
Expediting procurement and design is estimated to cos an additional $28,000.
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Robert W. Reid February 1,1979 In addition to the costs associated with performing this modification during an outage for this specific purpose, the District does not consider it desirable to perform this modification during any outage before the next refueling outage because of the higher radiation levels in the area of the modification with the reactor vessel head in place.
Radiation levels averaging 200 mr per hour in this vicinity would result in a significantly higher exposure over that which would be received if the work were performed on the service structure with the reactor vessel head in its storage location for a refueling outage.
Sincerely yours,
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' J. J. Mattimoe Assistant General Manager and Chief Engineer
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PROPOSED SEAL PLATE STORAGE STRUCTURE RAEHO SECO UillT tl0. 1 yp Existing Monorail for Stud Tensioner Hoist Existing Bracket
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- Seal Plate in Storage 7 11 1
- 1I i 1 ll 1 1 I I l L.!LJ Service Structure Storage Structure Position when Seal Plate is Lowered l
Reactor Head Seal Plate in Position bA a
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'A Reactor Vessel
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