ML19294C046
| ML19294C046 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 02/28/1980 |
| From: | GEORGIA POWER CO. |
| To: | |
| Shared Package | |
| ML19275C262 | List: |
| References | |
| TAC-11660, NUDOCS 8003060582 | |
| Download: ML19294C046 (9) | |
Text
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Table 3.2-9 INSTRUMENTATION WilIC11 INITIATES RECIRCULATION PUMP TRIP Required Ref.
Instrument Trip Operable Trip Setting Remarks No.
Condition Channels (a)
Nomenclature per Trip
, System (b) 1 Reactor Water vel Low Low I
> -38 inches Power must be reduced and the (ATWS RPT)
(LL2) mode switch placed in a mode other than the RUN Mode.
2 Reactor Pressure liigh 1
5 1120 psig Power must be reduced and the (ATWS RPT) mode switch placed in a mode other than the RUN Mode.
Turbine Stop('d 1
1.
Stop Valve Trips recirculation pumps on Valve Closurc 5 90% Open turbine control valve fast 2.
Turbine Control 2.
Control Valve e,losure or stop valve closure F
Valve Closure IIydraulic When reactor is >30%.(c)
[
Press Trip o
Point (a) The column entitled "Ref. No." is only for convenience so that a one-to-one relationship can be established between items in Table 3.2-9 and items in Table 4.2-9.
O (b) Whenever the reactor is in the RUN Mode, there shall be one operabic trip system for each parameter for Q
each operating recirculation pump, except that one trip system may remain inoperable for up to 14 days.
If this cannot be met, the indicated action shall be taken.
N Q
(c) Anticipated Transients Without Scram - Recirculation Pump Trip (d) End of Cycle - Recirculation Pump Trip (e) Either of there two EOC - RPT systems can trip both recirculation pumps.
Each EOC - RPT system will trip if 2-out-of-2 fast closure signals or 2-out-of-2 stop valve signals are received.
N M
Table 4.2-9 CHECK AND CALIBRATION MINIMUM FREQUENCY FOR INSTRUMENTATION WHICH INITIATES RECIRCULATION PDIP TRIP Ref.
Instrument Check Instrument functional Test Instrument Calibration No.
Instrument Minimum Frequency Minimum Frequency Minimum Frequency (a) 1 Reactor Water vel Once/ day Once/onerating cycle Once/ operating cycle (ATWS RPT)(
2 Reactor Pressure None Once/ operating cycle Once/ operating cycle (ATUS RPT) 3 EOC - RPT Trip (b) a) Initiating Logic (c)
None Once/ month None b) Breakers None Once/ operating
.-l e None c) Response Time None Once/ operating cle None RPT logics + Breakers Y
w Notes for Table 4.2-9 (a) The column entitled "Ref. No." is only for convenience so that a one-to-one relationship r be established between times in Table 3.2-9 and items in Table 4.2-9.
(b) If one EOC-RPT system is inoperable for longer than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or if both EOC-RPT systems
.imultaneously inoperable, an orderly power reduction will be immediately initiated and reactor power 5 ie <30% within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
(c) The RPT system may be placed in an inoperable status for up to 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> to provide the required conthly surveillance.
(d) An ATWS recirculation pump trip logic system functional test shall be performed once per operating cycle.
BASES FOR LIMITING CONDITIONS FOR OPERATION 3.2.H.5.
Rain Steam Line Radiation Monitors (Continued) the reactor through the main steam lines to the condenser.
Two instrument channels with two radiation detectors in each channel are arranged in a one upscale per channel trip logic (one-out-of-two-taken-twice).
The trip settings are based on limiting the release of radioactivity via the normal ventilation path an6 rerouting this activity to be processed through the standby gas treatment system.
I.
Instrumentation Which Initiates Recirculation Pump Trip (Table 3.2-9)
ATWS - RPT The ATWS recirculation pump trip has been added at the suggestion of ACRS as a means of limiting the consequences of the unlikely occurrence of a failure to scram during an anticipated transient.
The resp 6nse of the plant to this postulated event falls within the envelope of study events given in General Electric Company Topical Report NED0-10349, dated March, 1971 and Appendix L of the FSAR.
EOC - RPT An end-of-cycle recirculation pump trip (EOC-RPT) Fas been installed which trips both recirculation pumps upon sensing turbine stop valve or fast control valve closure.
The prompt RPT is comprised of two separate systems, each capable of tripping both recircu-lation pumps.
Tripping the recirculation pumps reduces core flow, which reduces void collapse during pressurization events. The reduced void collapse produces a smaller net positive void reactivity addition which results in less of a power increase and consequently a smaller decrease in ':CPR.
J.
Instrumentation Which Monitors Leakage Into The Drywell (Table 3.2-10) 1.
Drywell Equipment Drain Sump Flow Integrator The equipment drain sump is provided with two sump pumps. A flow integrator is provided on the discharge header. The starting of each sump pump and high sump level are annunciated in the control room.
The restarting frequency of a pump motor, in conjunction with the predetermined volume of liquid pumped out during each period, provides an alarm in the main control room indicating when the identified leakage rate limit is reached.
2.
Drywell Floor Drain Sump Flow Integrator The floor drain sump is provided with two sump pumps. A flow integrator is provided on the discharge header. The starting of each sump pump and high sump level are annunciated in the control room.
The restarting frequency of a pump motor, in conjunction with the predetermined volume of liquid pumped out during each period, provides an alarm in the main control room indicating when the unidentified leakage rate limit is reached.
3.
Scintillation Detector For Monitoring Air particulates A sodium-iodine scintillation detector contair.ed in an instrument rack is used to monitor the release of airborne radioactive particulates in the drywell and torus. A high radiation level reading is indicative of a leak in the nuclear system process barrier in the primary containment.
A sample that is continu-ously drawn from the primary containment is collected on traveling filter paper and monitored by a gamma sensitive scintillation detector.
Radiation levels are read out by a log rate meter and recorded on a strip chart located in the control room. A high radiation level alarm and a failure alarm are provided and are annunciated in the centrol room. Also, a high-low flow alarm is pro-vided which annunciates in the control room.
3.2-67
BASES FOR LIMITING CONDITIONS FOR dPERATION 4.
Scintillation Detector For Monitoring Radiciodine A sodium-iodine scintillation detector contained in an instrument rack is used to monitor the release of radiciodine in the drywell and torus.
A high radiation 3.2-67a
ENCLOSURE
~
REQUEST FOR ADDITIONAL INFORMATION HATCH UNIT 1 END-0F-CYCLE RECIRCULATION PUMP TRIP 1.
The proposed Technical Specifications combine E0C-RPT with the ATWS-RPT. The LCO's and surveillance requirements for these two different RPT's are not comparable.
Propose Technical Specifi-cations separate from the ATWS-RPT which provide for the EOC-RPT that:
a.
Each RPT system may be placed*'in an inoperable status for required surveillance for up to 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> per month.
b.
If one EOC-RPT system is inoperable for longer than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or if both EOC-RPT systems are simultaneously inoperable, an orderly power reduction will be immediately initiated and reactor pawer will be < 30% within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
c.
The RPT logics will be functionally tested monthly.
d.
The RPT circuit breakers will be functionally tested during each refueling outage.
e.
The response time of the RPT logics and breakers will be measured during each refueling outage.
It is desirable to indicate by footnote that: either of the two EOC-RPT systems can trip both recirculation pumps.
Each EOC-RPT system will trip if 2-out-of-2 fast closure signals or 2-out-of-2 stop valve signals are received.
2.
a.
The protective actions of the E0C-RPT must be independent of control systcm actions.
We consider broaker tripping to be the protective action and breaker closing to be a control system action.
Similarly, protective relaying, such as over-current protection, does not relate directly to nuclear l
safety.
Discuss the features of the proposed EOC-RPT that provides suitable independence between protective actions and control system actions.
No fault of the control system (e.g., blown fuse) should render the protection system to be inoperable.
b.
The E0C-RPT logic requires electric power to function.
Describe how the system will provide timely status indication to the reactor operator in the case of a blown, fuse.
3.
Describe the purpose, physical location, and actuating conditions for the following contacts of the RPT circuits, as shown on print H17822, Sh. 17.
3A, 3B, 4A, 4B, H
H H
H 3A, 3B, 4A, 40 CS CS CS CS 4.
Print H17822 Sheet 17 refers to the following prints:
H17860, H17862, H17863 H17902, H17904, H17905 Please provide copies of these prints.
The following disctission is in response to your questions on August 17, 1979, relating to a proposed change to the Edwin I. Hatch Nuclear Plant, Unit 1.
This change, if approved, will incorporate an end-of-cycle recircu-lation pump trip. The questions are answered in the order they were submitted.
1.
This question was actually a statement suggesting surveillance requirements which should be included in our Technical Specifica-tions in order to provide proper testing once the system is in-stalled. These changes have been incorporated in our latest pro-posed change and are included in Table 4.2-9.
The suggested foot-note was also included in Table 3.2-9.
In addition to the questions posed here and in anticipation of another round of questionk relating to this subject, we offer our plan to perform the required testing, including the response time testing. The RPT feature is required to interrupt the pump motor cituait within 175 milliseconds of the start of valve closure.
Of this, 10 milliseconds is allotted for system action and sensor response, 30 milliseconds for logic response and 133 milliseconds for breaker action. Westinghouse, the breaker manufacturer, at the direction of GPC performed tests to prove this action.
The results of the tests proved that the breaker's response time is significantly less than the 135 millisecond requirement and is therefore qualified to perform the RPT function.
The capability to check the RPT sensors and logic is provided by operating each valve one at a time.
Lights across the relay contacts (see H17822) in the logic indicate proper operation at that point. The RPT systems do not need to be bypassed to conduct such tests. However, during the periedic testing of the scram logic, where two valves are operated simultaneously, the affected RPT system must be bypassed briefly to prevent RPT actions.
Appropriate Technical Specifications cover this situation. The RPT circuit breakers will be functionally tested during refueling outages.
The response time testing, which is required each operating cycle, will be performed in sections and then the resulting times will be added. Existing plant procedures provide the testing of system action and sensor response separately from the logic response.
Once these rm ponse times have been obtained, they are added in a separate prc. : dure.
This will provide the necessary information to determine the section of the circuit which is not meeting the design response.
This will simplify the corrective action needed in case the response times drift out of specification.
The breakers will cach be tested separately in an unloaded condition.
In discussions with our electrical engineers, their view is that testing these breakers in an unloaded condition will provide equal assurance, as compared to a loaded condition, that the breakers will respond within the allotted response time.
A log of the results obtained each refueling outage will be kept in our records, so that any drift in the response time in the nonconservative direction will be noted and corrective action will be taken.
MRD/mb 2/28/80 Page 1
The reason for not testing this system fully loaded is to prevent the degradation of equ.pment which is necessary for operation of the plant. The most significant problem in tripping the recircu-lation pumps from a fully loaded condition is the tendency to rupture the pump's seals. Replacement of these seals is a major task which will cause additional down time and increase exposure to plant personnel.
It is our view that the testing program outlined above meets all the requirements to insure timely operation of the end-of-cycle recirculation pump trip.
2 2.a Breaker closing is accomplished by operating the breaker close switch (S13A on print H-17822) which activates the breaker closing coil. Releasing the control switch returns it to its " Normal" position which opens the contact that signaled the breaker to close, thus deenergizing the close control portion of the circuit.
During normal startup both RPT breakers must be closed in order to energize the Recirculation Pump.
Therefore, if the closing of the breaker caused problems and this resulted in a loss of power (i.e., blown fuse) to the control circuit and the protective circuit, it would annunciate (via K25A) and this would occur prior to Recirculation Pump energization. Note that the logic system doesn't become energized until contacts 9A and 9B close and this occurs when the reactor power is greater than 30% as signaled by 1st stage turbine pressure. Therefore, as shown above, if a fault of the control system (i.e., blown fuse) should render the protection system inoperable, it would do so during iniLial startup conditions at which time the protection system would be in a deenergized state. As noted above, loss of power annunicates (via K25A) in the control room and this would initiate operator response which would be to delay startup until the condition was corrected. The only load normally on this control system is 4 indication lights which provide the condition of the breaker (opened or closed).
From the explanation presented here, we believe suitable independence is provided betueen the protection (tripping) and closing circuits of the breakers.
2.b Since the RPT breakers require electric power to trip, undervoltage relays designated K25A and K25B are provided in each logic system.
This relay will instantly annunciate in the main control room the loss of logic power. This system will then be declared inoperable and within Technical Specification limits the cause of the loss of power will be corrected or appropriate action as defined therein will take place.
3.
The designations 3A/CS,3B/CS,4A/CS and 4B/CS represent contacts of a breaker control switch which is mounted on the front door of the RPT switchgear. This switch is used only during testing when the breaker is racked into the test position. This limited use is assured by the contacts designated 3A/H, 3B/H, 4A/H and 4B/H uhich are located inside the switchgear compartment and operate only when the breaker is racked into the test position.
This test position switch is also used to assure positive safety to testing personnel, such that when inspec-tion is taking place, no inadvertent trip signal will cause the MRD/mb 2/28/80 Page 2
breaker to operate. Positive return action of this feature of the test position switch is assured by the use of a monitoring light which must be illuminated when the breaker is closed from the main control room.
This light is located directly above the main control room close switch.
This method of indicating trip coil circuit continuity has been widely used throughout the industry on Class IE and non Class IE systems.
4.
Two copics of the prints requested are attached to this transmittal.
MRD/mb 2/28/80 Page 3