ML19330C432
| ML19330C432 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 08/06/1980 |
| From: | Nichols T SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8008080375 | |
| Download: ML19330C432 (8) | |
Text
{{#Wiki_filter:_ un-SOUTH CAROLINA ELECTRIC a GAS COMPANY I post orrect son,s4 COLUMBIA,$OUTH CAROUNA 29218 T.C. N ICH OLf'1. J m. %cs Persioter ano Onoue tarcurryt August 6, 1980 (Nuclear Operations) Mr. Harold'R. Denton, Director Office of Nuclear Reactor Regulation ~ U. S. Nuclear Regulatory Commission Washington, D. C. 20555
Subject:
Virgil C. Summer Nuclear Station Docket No. 50/395 Potential Design Deficiencies in Bypass, Override, and Reset Circuits of Engineered Safety Features
Dear Mr. Denton:
South Carolina Electric and Gas Company, acting for itself and as agent I for South Carolina Public Service Authority, herewith files twenty-five (25) copies of the response to questions' transmitted in Mr. Schwencer's letter of May 14, 1980 regarding the potential design deficiencies of engineered safety features.for the Virgil C. Summer Nuclear Station'. Very truly yours, J T. C. Nichols, Jr. KWN:TCN:rh cc: H. T. Babb -G. H. Fischer W. C. Mescher W. S. Murphy-W.;A. Williams, Jr. .T. B. Conner T. C. Nichols, Jr. B..A. Bursey-O. S.-Bradham E. H.ECrews, Jr. NPCF/Dixon' File 8008080375' g w
- 1) De overriding of one type' of safety actuation signal'(e.g., particulate radiation) should not cause the blocking of any other type of safety actuation signal (e.g., iodine radiation, reactor pressure) for those
- valves that have no function other 'than containment isolation. -Summer Station Design: ne Sunnaer Station design has'been reviewed against the above criteria. %e overriding of safety actuation signals is done at the individual safety actuation signal level' rather than at the actuated component Jevel'. His selective overriding of safety actuation signals precludes unintentional blocking of other types of safety actuation signal than the one selected. O \\ n + ? s
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- 2). Physical features (e.g., key lock switches) should be provided to ensure adequate e.iministrative controls.
Sursner Station Design: The Summer. Station design uses a " seal-in" or " latched" design' for indi-vidual components to-physically prevent, cc:aponents from returning to - their pre-actuation signal condition.upon actuation signal reset. Redun-
- dant manual reset consisting of two momentary contact control switches are provided on the control board.for deliberate operator reset of the actuation signal. The' manual override of a safety actuation signal is annunciated as indicated in item #3.. Administrative procedures are used by operations to control operator actions during ESF actuation conditions.
'Ihis combination of design and procedural control allows for adequate administrative controls without the use of additional physical features. t 4 5 -., - ~ -.,,,,a w w-,,
- 3) A system level annunciation of the overridden status should be provided for every safety. system" impacted when any override is active.
(See Regulatory Guide 1.47). Summer Station Design:- ~ The Sucuner-Station design provides for annunciation of override of safety - actuation signal. FSAR Table 7.1.2 and answer to NRC question 031.49 identifies Summer Station conformance to Regulatory Guide 1.47. O l-m- a e -o ,:. p y e -y >y- .y
- 4) ne following' diverse signals should be' provided to initiate isolation of the' containment purge / ventilation system:
containment high radiation, safety injection actuation, and containment high pressure (where contain-- ment high pressure is not a portion of safety injection actuation). Summer Station Design: ne isolation of the containment purge system is initiated on a High radiation signal and safety injection actuation which includes containment High pressure. -(Ref. FSAR Figure 7.2-1 Sheet 8) G 4 i 1 4 e v + ew,
- 5). The instrumentation systems provided to initiate containment purge ventilation -
isolation should be' designed and qualified to Class 1E criteria. . Summer Station Design: The instrumentation system provided to initiate containment purge isolation on.a safety injection signal is designed and qualified to 1E criteria. - In order to ensure the reliability of the isolation' system, the radiation monitors used to initiate containment purge isolation on a High radiation signal are on ' emergency power supplies and interface with the control cir-cuits'of the~ purge isolation valves via relay buffers. While radiation monitors themselves are not qualified to 1E criteria, some of the radiation monitors providing these radiation interlocks are seis-mically qualified. These radiation monitors and their features are de-scribed in FSAR Section 11.4 and 12.2. T 4 e f I: 'hi l' -_m.
- 6) 13e overriding' or resetting of -the ESF actuation signal should not cause any; equipment to change' position.
Summer StationLDesign: ' The Summer ' Station ' design of the ESF has been reviewed to determine if any actuated equipment would change its position following the' overriding or resetting of the -safety signal.- The criteria utilized' included: I) Verification'that a " seal-in" feature exist at the actuated component level'. II) Verification that no automatic signal, other than motor protection (undervoltage, overcurrent...), would call for an equipment position diffe' rent than the' safety position. The result of'the review indicates the following:- a) ~ Battery Room A and B supply dampers XDP-155-AH and XDP-153-AH: - These dampers are normally in the open position and would be closed automatically on a. battery room temperature ofaC 40*F. The temperature switches are class 1E. Resetting of the actuation signal will reopen the damper, but such action will not prevent the temperature interlock from functioning as designed. Based on this evaluation, there are no potential problems associated with these dampers during an acutation signal reset and no corrective action is planned. b) CVCS Letdown Orifice Isolation Valves XVT-8149A, XVT-8149B and XVT-8149C: Upon a reset of the actuation signal, these orifice isolation valves used for containment isolation will remain closed as designed; however, 4 the Train A solenoid on each valve does not have a valve limit switch . contact " seal-in" interlock to ensure that reopening does not occur. Based on this evaluation an additional " seal-in" interlock will be added j. to each Train'"A" solenoid on each orifice isolation valve. l 'c) FW Bypass Control Valves IFV-3321-FW, IFV-3331-FW, and IFV-3341-FW: ) FW Control-Valves FCV-478-FW, FCV-488-FW, and FCV-498-FW- . 1 ' Upon a reset of the actuation signhl, these valves will go on modulation; - however, reset of the signal will not reopen the FW isolation valves (XVG-1611--A, XVG-1611-B, and XVG-1611-C). l 1 Based on this evaluation no corrective action is planned. id) ' Component Cooling Water Booster Pumps XPP-5bA, XPP-58B, and XPP-58C: Upon reset of the actuation signal,. these non-safety-related pumps may ' restart against a closed. discharge line and consequently affect pump reliability. we i b .,,,,c g .r.., .,,,.w,,,, ,-4e
g,. e; ^ ~6) d) continued: Based ~ on this-evaluation the control circuitry for these pumps will be revised to include a discharge valve limit. switch interlock to preclude a restart of a pump against a closed discharge valve. O t T a O
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