ML17192A526

Responds to NRC Requesting Addl Info Re Containment Vent & Purge Sys.All Valves Modified to Require Closed Position for Control Switches Prior to Manual Reset. Drawings Available in Central Files Only

ML17192A526
Person / Time
Site:	Dresden, Quad Cities
Issue date:	02/28/1980
From:	Janecek R COMMONWEALTH EDISON CO.
To:	Ippolito T Office of Nuclear Reactor Regulation
Shared Package
ML17192A527	List: ML17192A526
References
TASK-06-04, TASK-6-4, TASK-RR NUDOCS 8003030373
Download: ML17192A526 (4)

Text

CommonweaA:dison One First National~, Chicago, Illinois Address Reply to: Post Office Box 767 Chicago, Illinois 60690 Mr. Thomas A. Ipp::>lito, Chief Operating Reactors - Branch 3 Division of Operating Reactors.

• u.s. Nuclear Regulatory Corrunission Washington, DC 20555 February 2~, 1980

Subject:

Dresden Station Units 2 and 3 Quad Cities Station Units 1 and 2 Resµ:>nse to Request for Additional Information Concerning Containment Vent and Purge Systems Refer~nces (a): T. A. Ipµ:>lito letters to D. L. Peoples dated January 21, 1980 (l;?): c. Reed letter to Messrs. T~* A. Ipµ:>lito, D. L. Ziernanp, and A. Schwencer dated January2, 1979

Dear Mr. Ipµ:

>lito:

Reference (af *requested a resµ:>nse within thiity days to questions concerning the containment vent and*purge systems at Dresden Units 2 and 3 and

. Quad Cities Units 1 and 2, The attachment to this.. letter contains o0r*: resµ:>nses to those questions for Dresden 2 and 3 and Quad-Cities 1 and 2. Also 'enclosed are* process and instn.unentation (P&ID) and* s<::herriatic drawings of" the vent and purge system*

for each of the four units,.

Please address any additional questions*. you may have concerning this matter to this office.

One (1). signed original and fifty-nine (59) copies of this letter and Attachment and two (2) copies of the drawings are provided for your use.

Attachment Very truly yours,

• ~~

Robert F. Jfnecek Nuclear Licensing Administrator.L.

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Question lt. l:

Response: 1.1

_ Q u e s t i on L..-2 :

Response

1.2 Attachment Dresden Units 2 ~ 3, Quad Citi~s Units 1 & 2 "The over-riding of one type of safety actuation signal should not cause the blocking of any other type of safety

• actuation signal to the isolation valves."

The override of containment vent isolation valve initiation logic is only perf6r~ed, by procedure, to verit the ~ontainment to the*Standby Gas Treatment System

( SBGTS) following a LOCA.

• Both high drywel l pressure and reactor low water level signals may be overridden in order to decrease containment* pressure after an accident.

The bypass circuit~y involves the permissi~e

_to open two 2-inch globe vent valves, (one at a time) one from the drywell and one from the suppression chamber~

and an outboard 6-inch butterfly valve to SBGTS. *The latter valve has been modified, in*accordance with an NRC commitment, to bave its* open travel

~estricted to less than 50 degrees.

All three of these valv~~ are closed during normal plant operation,' and no testing nor*

operatfons are performed :to inhibit or override the isolation initiation ~ignals.

The rem~ining containment vent-and purge valves' closufe cannot be qverridden. *(See reference 2, "Over-ride Circuitry", Item 2.)

"Sufficient physical* features should be provided to facilitate-adequate administrative controls."

The above override cir~uitry. is accessible only through use o~.a manual key-lpck switch in the Control Room.

Procedural controls *are in effect.which limi.t its usage to.post..,LOCA con:tainment venting.:. (See reference 2~*

"Override circuitry", Item 2). * *

"The system level annunciation of the o~er-ridden status should be provided for e~ery safety system impacted when an over-ride is act{ve.

11

Response

1.3 U~on manual actuation of the keylock switch, a Control Room alarm will annunciate, indicating that the bypass circuitry is in effect.

(See Reference 2, Items 2 & 3)

Question 1.4:

"Diverse signals should be provided.to.initiate isolation of the containment ventilation."

Response

1.4 Containment vent isolation valve closure (Group II) is initiated from either high drywell pressure (2 psig) or reactor vessel low water level {+8 inches).

The high drywell pressure setpoint is the same as for ECCS initiation.

The reactor vessel low water level setpoint is the same as for reactor scram, Reactor Building Vent isolation, and SBGTS auto-start.

These two signals provide adequate and early warning such that valve c 1 o s u re s a r e i n i t i at e d i n ad v an c e of _p_o s s i b le s u b s e q u e n t low low reactor water level, containment high radiation, and containment high hydrogen concentration conditions.

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Question 1.5:

Response 1.5:

Question l. 6:

Response 1.6: "The instrumentation and control systems provided to initiate ESF should be designed and qualified as safety-grade equipment."

The instrumentation and control systems were designated safety-related and were qualified as such in accordance with accepted practice at the time of design.

"The overriding or resetting of the isolation actuation signal should not cause the automatic motion of any ESF valve."

All containment vent and purge isolation valves have recently been modified to require that the control switches be placed in the CLOSE position prior to manual reset, before the valves have a permissive to be re-opened after a Group II isolation.

Usage of the override switch for post-LOCA containment venting requires that the override switch be placed to either the DRYWELL or TORUS position to be able to vent the drywell or suppression chamber, respectively.

With the control switches for the appropriate valves in the CLOSE position, the valves will not open upon actuation of the override switch.

Procedural controls exist to place the control switches for the 2-inch vent and 6-ihbh vent to SBGTS valves in the CLOSE position prior to commencing post-LOCA containment venting.

References

1.

Letter from T.A. Ippolito (NRC) to D.L. Peoples, dated 1-21-80.

2.

Letter from C. Reed (CECo) to Messrs. Ippolito, Schwencer, Ziemann (NRC) dated 1-2-79.

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Dresden 3:

DRESDEN/QUAD CITIES CONTAINMENT VENT AND PURGE DRAWING LIST M-2s, 12E2so1, Ci2-E2sci2, :-12:E-2so2A.-, *-12E-2s11r;-i2E2s1~(- ----

M-356, 12E3501, 12E3502, 12E3502A, 12E3511, 12E3512 Quad Cities 1:

M-34, 4E~501D; 4El503A, 4El503B, 4El509A, 4El509B Quad Cities 2:

M-76 Sht. 1, 4E2501D, 4E2503A, 4E2503B, 4E2509A,

.4E2509B