ML19338C686
| ML19338C686 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 08/07/1980 |
| From: | Widner W GEORGIA POWER CO. |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| TAC-07939, TAC-07940, TAC-7939, TAC-7940, NUDOCS 8008180455 | |
| Download: ML19338C686 (6) | |
Text
.
Gecrg a Puer Ccreany 230 Peac~'ee S:reet Post Cace 8 3 4545 M arta G-c g a 30K2
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Georg. Power a
W. A. Widner August 7,1980 ce mes ce~ am ar-e.a vara;,.
sc' ear oe eam U. S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Washington, D. C.
20555 NRC 00CKETS 50-321, 50-366 OPERATING LICENCES DPR-57, NPF-5 EDWIN I. HATCH NUCLEAR PLANT UNITS 1, 2 SCHEDULE FOR THE IMPLEMENTATION AND RESOLUTION OF THE MARK I CONTAINMENT LONG TERM PROGRAM GENTLEMEN:
A meeting with the Nuclear Regulatory Commission was held on July 3, 1980 to report on previous plant modifications and to provide a schedule for the installation and completion of future plant modifications in accordance with the ongoing Mark I Long Term Program. This communication serves to document pertinent aspects of the presentation including the planned modi-fications and schedule.
Since the inception of the Mark I Program and the subsequent reevalua-tion of suppression pool hydrodynamic loads, modifications have been performed on both plants as the need was identified. These modifications have been carried out on a rational basis to strengthen the torus shell and related structures, to shield the structure from hydrodynamic load impact, to increase the reliability of operating components and to introduce load mitigation devices where the uncertainty of the load magnitude dictated a need for l
prudent action.
On Plant Hatch Unit 1 Georgia Power Company has strengthened the torus support column to shell welds, reinforced the torus support column connection to the torus, installed anchor bolts in the base plate of each torus support l
column, increased the reliability of main steam safety relief valves (SRV),
I installed SRV line pressure monitors, implemented a dry well/ wet well pressure differential ( AP) load mitigator and perfonned plant unique SRV testing to l
l quantify the torus shell structural response with the current ramshead con-i figuration.
Georgia Power Company has performed similar modifications on Plant Hatch Unit 2 except that full saddles were installed during construction, vent l
header support attachments were increased in size and vent header deflector l
and downcomer ties were installed. These modifications were carried out on a l
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GeorgiaPower d U. S. Nuclear Regulatory Comission Office of Nuclear Reactor Regulation August 7,1980 Page Two continuing basis as the program progressed and because we considered them to be the most critici to plant safety. Modifications that are still to be perfomed are shown in the enclosure and enumerated below. Also, the en-closure elaborates on additional tasks and modifications to be performed during the outage.
Georgia Power Company will install eleven T-Quenchers per plant. This installation is not to be performed casually since a different circulation pattern will then be experienced by the pool. The flow is redirected per-pendicular to its original direction. As a consequence, submerged structures will be exposed to a different load distribution and pool circulation is decreased. Catwalk support columns and miscellaneous pipe supports have been identified to require modification as part of the LTP effort with a T-Quencher installed.
It is also Georgia Power Company's intention to install Residual Meat Removal test line elbows to promote pool circulation following T-Quencher installation.
It is Georgia Power Company's opinion that most submerged structure modifications should be completed prior to safety relief valve actuation with a T-Quencher installed. Georgia Power Company believes that the method detailed in the Load Definition Report (LDR) for predicting the torus shell structural response from main steam safety relief valve discharge is unrealistic. Cur options are to follow the LDR in its cresent format or resort to SRV testing along with a cotentially extensive effort to correlate the forcing function to shell struct. ural response for all loading combinations.
It is our desire to effect closure of the Mark I Program and to incur costs on a more structurally sound shell rather than testing and additional analysis.
We therefore opt to modify the torus shell to meet LDR criteria. With this stiffer configuration we expect to meet code without resort to testing and its associated analysis.
Georgia Power Company will retain the option to perfom safety relief valve testing should future activities indicate a need to do so.
Georgia Power Company plans to install thermowells in the torus shell because of the requirement for a temperature monitoring system.
Gerogia Power Company plans to install two ten inch vacuum breakers on each safety relief valve line. We expect delivery by the end of March 1981 and plan installation during subsequent refueling outages.
As previously indicated, vent header deflectors and downcomer ties were recently installed on Hatch 2 and will be installed on Hatch I during the next refueling outage.
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GeorgiaPower A U. S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation August 7, 1980 Page Three Georgia Power Company plans to install selected safety relief valve discharge line intermediate supports on Hatch 2 in the torus air space and to reinforce the vent line at the safety relief valve discharge line penetra-tions on Hatch 1.
The analysis has not progressed sufficiently in some areas to provide a basis for predicting additional modification requirements. This is particularly true with regards to attached piping where the most significant loads are expected to be derived from shell motion. Since shell motion is normally one of the last pieces of information to be obtained, piping analysis tends to i
lag the rest of the analysis. Georgia Power Company does not expect many l
problems with this modification, but there can be some surprises and additional modifications may be required. Other miscellaneous modifications may be required as the analysis progresses.
Georgia Power Company plans to perform the bulk of the modifications on Hatch 2 beginning October,1980, and on Hatch 1 beginning January,1981.
It is noted that while additional modifications have been identified since our f
previous schedule conunitment to you, we are essentially meeting this schedule.
Georgia Power Company will install safety relief valve vacuum breakers during the refueling outages following receipt of these long lead time items.
These outages associated with the vacuum breakers i.re in the winter, 1981, for Hatch 2 and the spring,1982, for Hatch 1.
Since operation with partial Ramshead Tees and T-Quenchers is planned between outages, we have compared the characteristics of the two modes of operation. Using methods developed during the long term program, we have compared bubble frequency and shell input frequency for the two cases. Results indicate a Ramshead frequency to be slightly less than those with a T-Quencher.
We have further, examined classicial predictions of bubble radius versus frequency and find correlation With long term program results. Therefore stiffening the torus shell should result in a similar reduction in shell strucutral response for the T-Quencher and Ramshead configurations.
^
f The results of earlier evaluations and of plant unique testing with Ramshead were previously reported in our May 14, 1979 letter.
In view of these submittals and in conjunction with the modification to include a stiffer shell during the next refueling outages, the continued operationwith partial T-Quenchers and Ramsheads will not compromise plant operation or the health and safety of the public. Based on our evaluation of the effort required to l
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GeorgiaPbwer A U. S. Nuclear Regulatory Ccanission Office of Nuclear Reactor Regulation August 7, 1980 Fage Four install T-Quenchers during one outage, it is our estimate that each unit would be shut down for an additional three months beyond refueling, thus derpiving the Georgia electricity consumers the economic benefits of half a reactor year.
In order to avoid this unnecessary hardship to Georgia Power customers we have scheduled the installation of twenty two T-Quenchers, eleven in each unit, over the next two refueling outages for both plants.
These outages are October,1980, and winter,1981, for Hatch 2 and January, 1981, and spring, 1982, for Hatch 1.
Very truly yours,
.s
../ w W. A. Widner SW/RDB/mb Attachnent xc:
R. A. Thomas George F. Trowbridge, Esquire R. F. Rogers, III i
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