ML20086K974
| ML20086K974 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 12/09/1991 |
| From: | Schrage J COMMONWEALTH EDISON CO. |
| To: | Murley T NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation |
| References | |
| RTR-REGGD-01.097, RTR-REGGD-1.097 NUDOCS 9112160007 | |
| Download: ML20086K974 (5) | |
Text
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' Commonwsalth Edison n,
1400 Opus Place
- Downers orove, Illinois 60515 December 9,1991 Dr. Thomas E. Murley, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 2055S Attn:
Document Control Desk
Subject:
Quad Cities Station Units 1 and 2 Res ponse to Unresolved item; Availability of Required Reactor Level Indication
- NRCRocket Nca 50:25 Land.50 255
References:
(a) H.J. Miller to C. Reed letter dated December 13,1988; inspection Report 50-254/88027 and 50-265/88028 (b) M.A. Ring to C. Reed letter dated February 27,1991 Inspection Report 50-254/9'l002 and 50/256/91002.
Dear Dr. Murley:
Reference (a) transmlued the results of a November,1988 special safety inspection of the instrumentation system required for ast.,essing plant conditions during and following an accident, as specified in Regulatory Guide (RG) 1.97. The inspection report identified an Unresolved item (254/88027 03 & 256/88028 03) who respect to reactor level instruments 263-73A and 263-738. The Unresolved item indicated that these level instruments only provide accurate information when the recirculation pumps are tripped or operating at the minimum speed. Based upon this fact, the inspectors
- did not consider these instruments operable for level measurement within the scope of-
- HG 1.97.
L This Unrosolved item was revisited during a safety inspection in l
January,1991 (Reference (b)). Dating the inspection, Guad Cities Station committed to perform an analysis to determine whettier or not the reactor level indication required by RG 1.97 would be available to operators during accident and post-accident conditions.
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Dr. Thomas E. Murley December 9,1991 Commonwealth Edison has performed an analysis of reactor level indication instrumentation availability. This analysis is attached as an Enclosure. The analysis indicates that appropriato instrumentation has been provided which allows the oaerator to adequately monitor reactor water level during normal oport'lon, accident, anc post accident conditions. As a result of the analysis, three k Iindication instruments will be added to the RG 1.97 Program. These three additionw instruments provide reactor level information during normal operation.
Based upon the attached analysis and subsequent actions, the referenced Unresolved item (254/88027-03 and 265/88028-03) should be closed.
If there are any comments or questions, please contact me at 708-515-7283.
Respectfully,
/
' g/
/
John L. Schrage Nuclear Licensing Administrator Attachment cc: A. Bert Davis - Regional Administrator, Region Ill M.A. Ring - Chief, hngineering Branch, Region 111 M.J. Kopp - Inspector, Region ill G.M. Hausman - Inspector, Region lil L.N. Olshan - NRR Project Manager, Quad Cities T.E. Taylor - Senicr Resident inspector, Quad Cities i
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ATTACHMENT RESPONSE TO UNRESOLVED ITEM 254/88027-03 and 265/88028-03 CONCERN:
Instruments 263 73A(B) fall upscale with the recirculation pumps running (NOTE: Instruments 1(2) 263 73A(B) are actually transmitWs that feed instruments 1(2)-263106A(B) in the Control Room.)
TECHNICAL EVALUATION OF CONCERN:
During normal power operation, both recirculation pumps are running and the above instruments are upscale due to the location of their reference leg Instrument taps. This does not create an operational concern because numerous other instruments are designed to provide reactor water level indication to the operator in this plant condition. Instruments normally available to the operator are summarized in Table 1.
During a plant transient (i.e., scram) which does not present a significant challenge to either the containment (i.e., drywell pressure remains below 2.5 psig) or the emergency core cooling systems (i.e., reactor water level remains above - 50"), the recirculation pumps would not normally trip. The recirculation pumps automatically run back to minimum speed after feedwater flow decreases to less than 20% of rated. Run back of the recirculation pumps would allow instruments 1(2)-263-106A(B) to read onscale. These indications could be used for trending purposes but would still read slightiy higher than actual level. In this plant condition, normal plant instrumentation would be accurate and would be used by operations.
During the January,1991 inspections, a concern was raised that norrnal plant operation instrumentation was not inc' ded in the RG 1.97 Program.
To address this concern, three reactor level indication instruments per unit and their associated transmitters (1(2)-263-100A(B) and 1(2)-263-101), are being added to the Regulatory Guide 1.97 Program. These are category 3 instruments and cover the reactor water level range of -60" to +60" end
-42" to +358", respeciively.
in the event of a more serious accident that challenges the containment or emergency core cooling systems, the recirculation pumps would trip due to either LPCI loop select logic (initiated by a high drywell pressure signal at
+2.5 psig) or a low low reactor water level signal at -59". In this alant condition, instruments 1(2)-263-106A(B) are able to be used to c etermine reactor water level. Recorder 1(2)-640-27 also provides indication of reactor water level under these conditions. The "A" channel instrument and the "B" Channel recorder are qualified as category 1 instruments and cover the reactor water level range of -340" to +60 The "B" channel instrument also covers this range but the indicator is not included in the Regulatory Guide 1.97 Program because it is part of the circuit that provides a signal to a non-safety related computer point. (NOTE:
Appropriate signal isolation has been provided.)
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'As discussed during the insepction, a review of the UFSAR was conducted 1(2)-263-106A(B)JFSAR.1Two ofduring a d to assess the functions of instruments basis accident (DBA). Four DBAs are discussed in the d
1the accidents, control rod drop and refueling accident, are not associated i
with a loss of reactor water inventory. No conclusion could be drawn from the UFSAR review concerning the performance of the 1(2) 263-106A(B) for these accidents. The main steam line break outside containment and the 1
-loss of coolant design basis accidents were also reviewed. The UFSAR analysis for both events shows that each accident results in stoppage (trip or coastdown) of the reactor recirculation pumps.
The main steam line break outside of the drywell is discussed in Section 14.2.3 of the UFSAR. Section 14.2.3.9 addresses the affects of this event on core cooling.' The bounding conditions of this accident analysis includes the assumption of the simultaneous loss of normal AC power with the l
postulated break of one of the main steam lines. This event would result in the coast down of the recirculation pumps due to loss of power (the recirculation pump M G sets cannot be fed from the diesel generators).
L L
The loss of coolant accident (LOCA) is addressed in Section 14.2.4 of the UFSAR. The full range of coolant loss accidents have been analyzed.
The containment response is discussed in Section 5.2.3. Section 5, page 41, states that a scram will occur in less than a second from high drywell
~ pressure for the most severe break of a reactor recirculation loop. Figures-5-2.14 5-2.15,- and 5-2.17 support this statement. The high drywell r
aressure signal will inillate LPLI loop select logic which results in tripping -
aoth reactor recirculation pumps.
SUMMARY
Based on the above discussion, appropriate instrumentation has been 3rovided which allows the operator to adequately monitor reactor water evel during normal operation, accident and post accident conditions. To address NRC comments, three normal operation reactor level instruments are being added.to the Regulatory Guide _1.97 Program. (See
- items in -
Table 1). This action provides additional assurance that these instruments r
will receive appropriate attention during future maintenance activities.
l l'
L b
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NORMAL CONTROL ROOM REACTOR WATER LEVEL INSTRUMENTATION Table 1 Instrument Iransmitter Range Comments
- 1(2)-263-100A(1)_
1(2)-263 57A
-60 to +60 Narrow Range Yarway
- 1(2) 263-100B(I) 1(2)-263 598
-60 to +60 Narrow Range Yarway 1(2)-640-29A(1) 1(2) 646A 0 to +60 Narrow Range GEMAC 1(2)-640-29B(1) 1(2)-C46B 0 to +60 Narrow Range GEMAC 1(2) 640-26(R) 0 to +60 See Note 1
- 1(2)-263-101(l) 1(2)-263 61
-42 to +358 Wide Range GEMAC (Upper 400) 1-263-0113(R) 1(2)-263-112
-344 to +66 Wide Range GEMAC (Upper 400) 1 - Instrument R - Recorder
- Regulatory Guide 1.97 Instrument.
Note 1: This recorder displays the output of either 1(2)-604-2 t or B.
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