ML19256G112
| ML19256G112 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Quad Cities, Zion  |
| Issue date: | 12/14/1979 |
| From: | Peoples D COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| TASK-06-04, TASK-6-4, TASK-RR NUDOCS 7912270470 | |
| Download: ML19256G112 (6) | |
Text
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Commonwealth Edison one Forst Nationat Plata, Chicago, Ilhnois Address Reply to: Post Office Box 767 Chicago, litinois 60690 December 14, 1979 Mr. H. R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
Dresden Station Units 2 and 3 Quad Cities Station Units 1 and 2 Zion Station Units 1 and 2 Containment Venting and Purgi ng During Normal Operation NRC Docket Nos. 50-237/249/254/265/295/304 References (a): T. A.
Ippolito letter to D.
L.
Peoples dated October 22, 1979 (b):
D.
L. Ziemann letter to D. L.
Peoples dated October 23, 1979 (c): A. Schwencer letter to D. L.
Peoples dated October 23, 1979 (d): D. L.
Peoples letter to D. G.
Misenhut dated November 14,19'/9
Dear Mr. Denton:
References (a), (b), and (c) requested information for Dresden Units 2 and 3, Quad Cities, and Zion documenting that we are pursuing purge and vent valve operability verification on an expedited basis and have committed to operate the purge and vent system in conformance with an interim position provided in the References.
As indicated in Reference (d), we have initiated valve qualification programs for the vent and purge valves at the subject stations.
Results have already been submitted for your review in our September 25, 1979, letter to H. R. Denton for the vent valves at Zion 1 and 2.
Qualification programs for the remaining valves are in progress by original valve manufacturers, consulting en-gineers, and original NSSS vendors.
Preliminary, conservative analyses performed by our consulting engineer for the Dresden and Quad Cities butterfly valves indicate that the valves will close adequately regardless of degree of opening.
This has been confirmed by_a generic response from the valve manufacturer.
Complete con-firmatory analyses addressing all the concerns expressed in the 79122ID 1644 310
Mr. H. R. Denton December 14, 1979 Page 2
September 27, 1979, letter to all Light Water Reactors may not be available, however, for 30 to 40 weeks.
We are attempting to im-prove this schedule in discussions with the valve manufacturer and will provide an updated schedule when it becomes more firm.
These commitments to perform qualification pro $ rams supercede any previous commitments for valve testing or analysis.
Until the confirmatory analyses are complete, we will operate the vent and purge valves in accordance with the interim position identified in References (a), (b), and (c).
The method of compliance with the interim position is identified in Attachment 1 for Dresden Units 2 and 3 and Quad cities Units 1 and 2 and in for Zion Units 1 and 2.
Please address any questions you may have concerning this matter to this office.
One (1) signed oridinal and :eventy-nine ('/9) copi es of this transmittal are provided for your use.
Very t ruly you rs,
flbQf ct.a<>f
.ru D. L.
Peoples Director of Nuclear Licensing t
4 1644 311 i
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ATTACHMENT 1 Dresden Station Units 2 and 3 Quad Cities Station Units 1 and 2 Response to NRC interim position, Item 1:
Existing operating instructions already direct the operators to limit purging and venting times to as low as achiev-able for the containments.
The existing operating instructions include the provisions specified in paragraph 1 of the NRC Interim Position, while ensuring compliance with the Technical Specifications for inerting, deinerting, maintaining oxyden concentration, and maintaining the drywell to suppression chamber differential pressure.
Response to NRC interim position, Item 2:
Containment purge and vent butterfly valves greater than a.
3" nominal diameter will be limtted to less than fifty degrees (50 ) travel in the open direction, or remain closed except when the reactor is in the cold shutdown or refueling mode.
Preliminary, conservative analyses performed by our consulting engineer indicate that the valves will close adequately regardless of decree of opening.
This has been confirmed a generic response from the valve manufacturer.
The limited travel of less than 500 adds additional conservatism to ensure valve closure until confirmatory analyses are complete.
The only exception to the above commitment concerns the 1601-55 butterfly valves at Dresden Units 2 and 3 These valves are 4" nominal diameter and are used for nitrogen inlet to the containment for inerting and compressor suction line isolation for the drywell/ torus pump-back system (for maintaining drywell/ torus AP).
If restricted to 50 opening, the valves could cause sufficient flow restriction to cause the compressors to trip on low suction pressure.
In addition to the previously mentioned analyses for unlimited travel, we do not believe that the valves need to be restricted for the following reasons:
i 1.
Due to the small diameter of the valve, any loads imposed by a LOCA condition would be small and not expected to cause damage or prevent operation.
2.
All piping and components outboard from these valves have pressure capabilities greater than maximum con-tainment pressure.
The pump-back compressor piping is a closed loop returning to the containment.
Since these closed systems would not be over pressurized by 1644 317
2-the LOCA pressures, no uncontrolled escape to the environment would occur and high flows through the valves would not exist.
Therefore, valve operation is not expected to be compromised.
b.
The design of the isolation logic of the vent and purge valves is segregated.
Either low reactor water level or high drywell pressure will initiate the desired isolation.
If one of these two signals is reset, the other will provide the required protective action if needed.
Neither of these initiation signals are olocked nor overridden during normal reactor operation.
Therefore, no modifi-cations are dee:ned necessary.
1644 313
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6 ATTACHMENT 2 Zion Station Units 1 and 2 References (a):
C. Reed letter to Messrs. A. Schwencer, D. Ziemann, and T. Ippolito dated January 2, 1979 (b):
C. Reed letter to H. R. Denton dated July 2, 1979 (c):
D.
L.
Peoples letter to H.
R. Denton dated September 25, 1979 (d):
D. L.
Peoples letter to H.
R. Denton dated October 4, 1979 (e):
A. Schwencer letter to D. L.
Peoples dated October 23, 1979 (f):
D. L.
Peoples letter to D.
G.
Eisenhut dated November 14, 1979 Response to NRC interim position, Item 1:
In reference (b) Commonwaalth Edison stated that purging would be limited to an absolute minimum, not to exceed 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> per year per unit.
(Other Administrative Controls currently in effect prohibit purging when the reactor is critical.)
It was also stated that venting would be restricted to only those operations required to comply with the Technical Specifications that limit containment pressure.
Commonwealth Edison re-affirms thone statomonts at this time, and considers this position to be in conCormance with the NRC interim position.
Response to NRC interim position, Item 2:
i In reference (b) Commonwealth Edison Company stated that a.
analysis of the closure capability of the purge and vent valves would be performed.
That commitment was re-affirmed in reference (f).
Results of the vent valve analysis, which showed that these valves would close properly under accident flow loading, were transmitted in reference (c).
j In addition, an in-situ test was performed on the_ vent valves in which the valves successfully closed against a flow loading that simulated accident conditions.
In view of these results, Commonwealth Edison Company feels that the vent valves may be operated under the provisions of the NRC interim position, without limiting valve travel in the open direction.
1644 314
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'c, s Results of the analysis on the purge valves have not yet been obtained.
In the interim, the purge valves will be maintained closed whenever the reactor is not in the cold shutdown or refueling mode, in accordance with the NRC interim position.
b5'heIn' reference (a)CommonwealthEdisonCompanystatedthat yJf.there were no bypass or override features on the purge 1,.
'and vent valves for which adequate administrative con-
,h trols did not exist.
Consequently, no design changes were Typroposed.
At a subsequent site visit and in an NRC Staff
'h., Meeting held on June 28 and 29, 19/9, the NRC Staff in-
.s, dicated that there were no Staff Concerns with regard to V ','this item.
Commonwealth Edison re-affirmed this position
.h,j,inreference(d).
Since the NRC interim position does not allow for the use of administrative controls to govern the operation of Othe purge and vent valve override switcho's, Commonwealth 9,* Mdison Company will modify the override '.fcature to meet
'the requirements of the NHC interim posi. tion.
Pending
'ompletion of these modifications, the 6y'erride switches chave been temporarily removed from the valve actuatin$
circuit.
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