ML20010J009
| ML20010J009 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 09/24/1981 |
| From: | Vincent R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| TASK-06-04, TASK-6-4, TASK-RR NUDOCS 8109290495 | |
| Download: ML20010J009 (6) | |
Text
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Consumers Power Company o.n.r.: ome ; 212 W.st Michigen Av.nu., J.ckson, MI 49201 e (517) 7t8-0550
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September 24, 1981
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Director, Nuclear Reactor Regulation (k
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s Att Mr Denn.1 M Crutchfield, Chief Operating ' -ictors Branch No 5 k/[,
(3 US Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-155 - LICENSE DLt BIG ROCK POINT EANT - SF TOPIC VI.-h, CONTAINFEI;T ISOLATION SYSTH4 By letter dated December 2,1980, the NRC requested additional information concerning SEP Topic VI-4 for the Big Rock Point Plant.
The at,tached f a-formation is provided in response to that request.
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'T Robert A Vincent Staff Licensing Engineer CC Director, Region III, USNRC NRC Resident Inspector - Big Rock Point e
Attachment (5 pages) t 0g\\
8109290495 810924~
PDR ADOCK 05000 P
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O ADDITIONAL INFORMATION ON SEP TOPIC VI h, Containment Isolation System - Big Rock Point License DPR-6 Eocket 50-155 The following additicnal information is provided in response to your request dated December 2,1980, in a letter from DMCrutchfield to DPHoffman:
Question 1.
The information presented in your FHSR and your letters of August 7, 1979, September l'.,1979, March 14,1980 and June 15, 1980, is not sufficient to.
determine if tae following requirements are met for the safety signals to all Engineered Safety Features (ESF) equipment. Therefore, identify and justify all exceptions to the following:
a.
Criterion 1--7n keeping with the requirements of General Design Criteria 55 and 56, the overriding of one type of safety-actuation signal (e.g.,
radiation) should not cause the blocking of any other type of safety-actuation signal (e.g., pressure) for those valves that have no function besides containment isolation.
Response
The Big Rock Point design does not deviate from Criterion 1 above.
Question b.
Criterion 2--Sufficient physical features (e.g., key lock switches) are to be provided to facilitate adequate administrative controls,
Response
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Physical features have been incorporated irt _ the containment isolatim, cir-cuitry to prevent automatic reopening of the isolation valves after th( initiating signal clears. The physical features consist of seal-in re3 ays and push button switches in the control circuits. This information was provided in response-to the TMI Lessons Learned Category A Item II.E.h.2 and was accepted b y the NRC staff (reference May 2, 1980 letter from DLZiemann to DPHoffman). The informa-tion below.is excerpted from Consumers Power Companys response:
Following the rev3ev of containment isolation required by NUREG-0578, the problem of inad<ertent reopening of the isolation valves was found in four e
(h) control circuits which control nine (9) isolation valves. The nine j
valves are CV h031, LY h102 (enclosure clean sump discharge), CV h025, CV 4103 (enclosure dirty sump discharge), CV h091, CF-4902, CV h093 i
(clean-up cemineralizer resin sluice), CV h027 and CV hll7 (reactor and fuel pit drain). The automatic reopening of the isolation valves was eliminated through the addition of a seal-in relay and a push-button switch into each of the four (h) control circuits. The seal-in relays are General Electric Type HMA relays and the push-button switches are General Electric industrial miniature oiltight push-buttons. Zae seal-in relay j.
was installed in each isolation valve control cireu. before the isolation valve hand switch and in parallel with the circui'.
One normally open 4
contact sof the seal-in relay was placed in series with the circuit and
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2 before the seal-in relay coil to act as a holding contact. A push-button switch, with momentary contacts, vas irstalled so as to bypass the holding contacts. This provides a means or energizing the seal-in relay coil and closing the holding contact which, in turn, completes the circuit, provided that the reactor protection systems containment isolation signal is clear and the isolation valve's hand switch is in the closed position.
If loss of ac power should occur or reactor protection systems containment isolation signals should actuate, the seal-in relay coil vill tecome de-energized, dropping out the contact. '?-energizing of the circuit can only be accom-plished through a direct operator action via the push-button switch and only after the de-energizing signal is corrected or cleared.
Question c.
Criterion 3--A system level annunciation of the overridden status should be pro-vided for every safety system impacted when any override is active (see RG 1.h7).
Response
With the exception of the ventilation valves, the containment isolation valves do not have any override features.
The: containment ventilation valve circuitry is designed such that all close signals are overridden in the event-that a vacuum condition exists inside containment. There are two paths to relieve the vacuum; the supply and exhaust ventilation lines. Opening of the supply ventilation valves due to vacuum causes a control room annunciator to alarm in both an audio and visual mode. Opening of the exhaust ventilation valves results in a visual flashing alarm on the main control panel.
Question d.
Criterion h--Diverse signals should be provided to initiate isolation of the containment ventilation system.
Specifically, centainment high radiation, safety injection actuatien and containment high pressure (where containment high pressure is not a portion of safety injection actuation) should automatically initiate containment ventilation isolation.
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Response
The containment ventilation valves close on the following signals: reactor _ scram, containment high pressure, low reactor water level, containment high radiation and loss of power.
The low reactor water level setpoint used for containment isolation is the same as that used for initiation of core spray.
1 Question e.
Criterion 5--The instrumentation and control systems provided to initiate the ESF should be designed and qualified as safety-grade equipment.
i
Response
The instrumentation and control systems provided to initiate the ESF have been qualified as safety-grade equipment as-evidenced in Consuners Power Company's submittals on Environmental Qualification of Electrical Equipment dated October 31, 1980, January 30, 1981 and September 3, 1981.
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Question f.
Criterion 6--The overriding or resetting" of the ESF actuation signal should not cause any velve or damper to change position.
Response
The modification made to the containment isolation circuitry is explained in (b) above and was accepted by the NRC Staff treference May 2,1980 letter from DLZiemann to DPHoffhan).
Question 2.
The NRC requires that all override and reset switches have physical provisions to aid in the administrative control of the override or re3et function.
Discuss tge physical provisions supplied with your seven manual bypass contiol switches, indicating how you comply with this requirement.
Response
In a letter from DABixel.to DLZiemann dated September 11, 1979, consumers Power Company committed to install. audio and visual indication when any of seven valve control switches was placed-in the override (pull to stop) position. 'lb1 electri-cal scheme was designed to provide by-pass indication and alarm for the subject valve switches.
A single control room annunciator window has been designated " Engineered Safety
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Feature By-Pass Indication." When a valve control switch is placed in the over-ride position, the. annunciator momentarily lights and alarms. The circuit is provided with a timer and time delay relay such that the alarm circuit is momen-tarily interrupted every eight hours causing re-annunciation of any off-normal circuit. The operator can determine whether a valve control switch is in the override position at any time by observing that a white indicating light, located near the switch 1s extinguished.
3 Question 3.
The NRC requ: es that, at a minimen, containment ventilation isolation (CVI) be accomplished on any of the following:
a.
Containment pressure high b.
Safety injection c.
Containment radiaticn high.
Since your CVI valves do not isolate on manual actuation of safety injection, discuss how you meet this requirement.
Response
Big Rock Point's only " Safety Injection" systems are low pressure systems. Safety injection (core spray) does not automatically occur until a low pressure interlock is satisfied and the low reactor water level setpoint is reached. When the low reactor water level setpoint i.s reached, the containment automatically isolates.
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The core spray system piping design incorporates two (2) motor operated valves with a check valve between them,all in series.
If the operator manually opens the core spray valves, core spray cannot occur, due to the check valve, until the primary system pressure is less than the core spray header pressure.
Although manual operation of the core spray valves does not cause the CVI valves to close, any reactor scram signal vill cause them to close. It is inconesivable that an operator would manually open both core upray valves in either core spray system for the purposes of mitigating the consequences of a loss of coolant accident without M rst ensuring that the reactor is scrammed. On the other hand, if both of the actor opsrated valves in a core spray line are inadvertently opened, the check valve b"tveen the MOV's prevents primary coolant from flowing into the core spray piping.
In this case there is no accident and no need for the ventila-tion valves to be closed.
g_testion h.
The h4C requires signals that initiate containment isolation be derived from safety-grade (Class IE) equipment.
Discuss the qualifications of the equipment used presently and the equipment that is needed to meet Requirement 3 above.
Response
In response to NRC questions for information on the_ qualification of equipment to perform its function when subjected to accident environments (reference Topic j
III-12), Consumers Power Company has made submittals on October 31, 1980, January 30, 1981 and September 3,1981 providing the qualification date. For isolation of containment due to high pressure, pressure switches. PS-66h, PS 0 ',
PS &666 and PS-667 provide the necessary signal. Qualification data for thesc switches is provided on Pg 111 and 112 of the submittals referenced above. For 4
containment isolation due.to safety injection (see clarification statements in the response to 1(d) above), the level switches LS-RE09 A through H provide the necessary signal.
Qualification information for these switches is given on Pg 71 through 75(a) of the above referenced submittals. The ventilation valves close due to high containment radiation upon receipt of a signal f rom radiation monitors RE-8258 and RE-8259 Thece two instruments are not Class IE; however, justifi-l cation for deleting these instruments from the list of equipment required to be environmentally qualified was provided on Page 5 of the above referenced submittals.
i The basic arguments are as follows:
l 1.
The instruments are primarily intended to mitigate the consequences of a fuel j
handling accident (ie radiation).
2.
A large LOCA vould cause many and diverse scram signals. Since the ventilation valves close on any scram signal it is reasonable to assume the ventilation valves vould close due to the scram signal prior to core uncovery and fuel
- damage, i
Question 5.
SK-07h0Gh0125 shows all redundant CVI valves are located outside containment (for supply, exhaust and probe). General Design Criteria (GDC) 56 does not permit this. Discuss the acceptability _ofthe design on some other defined basis.
f 5
Responeg All of the CVI valves are indeed located outside containment in what is called the sphere ventilating room. This room is adjacent to the containment sphere but is unaffected by any HELB outside containment. For a LOCA inside containment this room experiences increased radiation levels only. There are no high energy Jines running through this room.
Since there are no postulated accidents that can cause a LOCA and failure of the penetration outside containment, the design is acceptable as is.
Question 6.
It appears from SK-07h0G30llh t'aat a failure of PISX2/173 (Zone D-2) could cause SV9151 to remain energized.
The-same type of circuit is used for PISX2/XXX (Zone F-2) and SV9152. Describe operation of these circuits'. Verify that failure of the vactum relief schemes vijl not prevenc the automatic isolation features from operating properly.
Response
For automatic containment isolation, each electrical scheme operates one series valve in the supply and exhaust ventilaticn lines. Scheme 8501 operates CV h094 and CV h006 while Scheme 8512 operates CV h095 and CV h097 If one scheme (either 8501 or 8512) is deenergized, one isolation control valve vill close in tne supply and exhaust ventilation lines.
For the purposes of containment vacuum relief, each electrical scheme operates both series valves in the supply or exhaust ventilation lines.
Scheme 8501 operates CV h096 and CV-h097 while Scheme 8512 operates CV h09h and CV h095 If one scheme (either 8501 or 8512) is deenergized, it results in the failure of both isolation control valves to open in the supply cg exhaust ventilation lines.
While it is true that failure of PISX2/173 could cause SV-9151 to remain energized, it would take a dual failure (failu-n of PISX2/190) to prevent automatic contain-ment isolation since they operate different "in-series" isolation control valves.