ML20032E302
| ML20032E302 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 11/10/1981 |
| From: | Swartz E COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8111200373 | |
| Download: ML20032E302 (3) | |
Text
-
a
/
s Commonwealth Edison
,1
_ ~J Address Reply to: Post Ofhce Box 767
/ One First National Plaza. Chicago. Ilhnois
(
,/ Chicago. Ilhnois 60699 November 10, 1981 Mr. Harold R.
Denton, Director Of fice of Nuclear Reactor Regulation U.S.
Nuclear Regulatory Ccmmission Washington, DC 20555
Subject:
Zion Station Units 1 and 2 ATWS Modifications (AMSICj NRC Docket Nos. 50-295/364 Re ferences (a):
H.
R. Denton letter to D.
L.
Peoples dated February 29, 1980.
(b):
D.
L.
Peoples letter to H.
R.
Denton dated April 28, 1980.
, [. Og<W / /Q (c):
S.
A.
Varga letter to D.
L.
Q {,D.(ly;,,.] ].3i j//
g.gi Peoples dated June 19, 1980.
L)i _ -
(d):
W F.
Naughton letter to H. R,h 9 jggp 1 Dt iton dated July 23, 1980.
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II
h, u,C**
g/
,y, u1 (e,':
L.
O. DelGeorge letter to H.
R.
Denton dated September 8, 1981.
.,,//,,q'
Dear Mr. Denton:
The Reference (a) Confirmatory Order for our Zion Station Units 1 and 2 was based upon the NRC Staf f belief that the Zion Site presents a disproportionately high contribution to the total societal risk from reactor accidents, due to the relatively high population density surrounding the Zioa site as compared to other nuclear power plant sites.
To that end, the NRC Staff identified a numoer of " extraordinary interim measures" believed to significantly increase the level of safety at the Zion Station and thereby further l
reduce the probability of a severe reactor accident.
Included among these actions was Item C.4 which required the submittal o f a schedule, within sixty (60) days of the Order, to implement the ATWS
..t;ument modification justified in accordance with the Westinot'
.cilytical results o f their report NS-TMA-2182, dated Decembe" 79.
The results of that report indicate that the Zion unite
.mstand the consequence of postulated ATWS events.
T he r t-are
..: (2) functions identified as necessary to A
o mitigate tre curscquence; of the most severe ATWS events prior to [f0D1 proceeding tn long term stwtdown conditions.
These functions are j
the tripping of the main turbine and the initiation of auxiliary feedwater within 30 and 60 seconds, respectively, upon sensing sO 8111200373 81111o DR ADOCK 05000295 p
PDR 3
l 1
H. R. Denton November ~10, 1981 the loss of heat sink. _'Normally, these functions are obtained via the reactor scram signal and through the rer.ctor protection -system.
Since these functions are postulated to be unavailable during an ATWS, the Westinghouse ATWS instrument modification provides for another method of guaranteeing. these functions independent of the -
Reference (b) provided the requested schedule to install this Westinghouse Alternate Mitigating Systems Actuation Circuitry
[
(AMSAC) concept.
However, no direction was given by the NRC Staff
~
)
us'to the requirec system design criteria to be employed.
There-fore, our schedule as based upon a conservative approach towards design, engineering and procurement activities with installation during scheduled refueling outages.
l Reference (c) took issue with the Commonwealth Edison proposed schedule.
The NRC Staff re-iterated their belief that because of the risk that Zion Station was believed to represent, we should improve upon the schedule required of other plants and requested that a revised schedule be submitted within thirty (30) days.
Reference (d) provided the requested improved schedule.
However, our response clearly took issue with the-NRC Staf f belief that our Zion Station representc an additional risk over and above other plants especially with regard to its AMSAC installation
. schedule.
Additionally, our response defended our originally proposed schedule as being very realistic for a variety of reasons as explained in the response.
This improvec schedule was based upon our definition of the technical design octails where guidance haa not been provided by the NRC Staff.
Our response stated that an improved schedule was possible, provided that an expeditious agreement could be reached with the NRC Staf f on our proposed AMSAC dasign.
In order to begin procurement activities and expenditures in pursuit of a January 1,1982, ' completion date, we requested prompt NRC approval of our design.
To date, there has been no acceptance of our proposed AMSAC system by the NRC Staff.
As a result, the final design and procurement of the Zion Station AMSAC equipment has not been accomplished.
Reference (e) transmitted the Zion Station Probabilistic Sa fety Study to the NRC.
That report' demonstrated on a probabilistic basis, that the risk associated with Zion Station is considerably less than had been previously estimated by the NRC Staff for either Zion Station or the WASH-1400 PWR.
The results of this study exem-plify our contention raised in Reference (d) regarding the NRC Staff perception that the Zion Station AMSAC installation schedule should be improved.
Because the study clearly demonstrated that the NRC Staf f concerns which led to the imposition of the " extraordinary interim measures" were unfounded, Re ference (e) respectfully requested that all ongoing provisions of the Order be rescinded.
o H.
R.
Denton November 10, 1981 As demonstrated in References (b) and (d), the Commonwealth Edison Company has been responsive to all NRC Staff submittal requirements for the Zion Station AMSAC installation.
However, in view of the results of the recently completed Probabilistic Safety Study, the installation o f any ATWS mitagation system provides essentially zero reduction in the already low levels of risk associated with ATWS events.
Therefore, in the judgement of the Commonwealth Edison Company, any further consideration of such an installation in advance of the generic resolution of the ATWS issue for all plants is wholly unjustifiable.
The Commonwealth Edison Company is a me,aber of the Utility Group on ATWS and is in support o f the Electric Utilities' Petition For Rulemaking On ATWS that was submitted to the NRC on September 16, 1980.
However, based upon the above and contrary to the Petition, we cannot support the provision of the automatic initiation of turbine trip and auxiliary feedwater independent of the reactor protection system (AMSAC) on our Zion units, without a clear understanding of the final criteria to be imposeo by the NRC Staff.
Unfortunately, notwithstanding our attempts to solicit Staff concurrence, final criteria have not been defined.
Please address any questions that you or your staf f may have concerning this matter to this of fice.
Your review o f our previously submitted design information is required in order for us to initiate procurement of necessary materials.
One (1) signed original and thirty-nine (39) copies of this letter are provided for your use.
Very truly yours, em #
E.
Douglas Swartc Nuclear Licensing Administrator cc:
J.
G.
Keppler, Director PIII Region III Inspector - Zion im 280lN