ML20031C567
| ML20031C567 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 10/05/1981 |
| From: | VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | |
| Shared Package | |
| ML20031C564 | List: |
| References | |
| NUDOCS 8110070304 | |
| Download: ML20031C567 (5) | |
Text
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VYNPS TABLE 3.2.2 (CONT'D)
E".
,,o" REACTOR CORE-ISOLATION COOLING SYSTEM ISOLATION INSTRUMENTATION y:
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Minimum Number of.
Required Action When i
um Operable Ins trument Minimum Conditions for 8"
Channels per Trip Operation are pot
. g$8[
' System' Trip Function Trip Setting Met (Note 2) l E"*-= !
2 Main Steam Line Tunnel l '
Temperature 12120F Note 3 l
1 Time Delay (13A-K41) i 35 minute'4 Note 3 l
(13A-K42)
L 2 per set of 4 liigh Steam Line Space Temperature 12120F Note 3 1
High Steam Line 4/p (Steam 1 195 inches Note 3 Line Break) of water 2 (Note 4) liigh Reac. tor Water Level Feme as IIPCI Note 3 4 (Note 5)
Low Steam Supply Pressure 1 50 psig Note 3 1
ras Power Monitor Note 3 1
Trip System Logic Note 3 1
Time Delay (13A-K7) 3<
t < 7 secs.
Note 3 (13A-K31) 43 4-n
< 'J N 9-e 9
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VYNPS l
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TABLE 3.2.2 NOTES
- 1. The main steam line low pressure need be available only in the "Run" mode.
- 2. If the minimum nu;oer of operable instrument channels is not available for one trip system, that trip syster.shall be tripped.
If the minimum number of operable instrument channels is not available for both trip systems, P.he l
appropriate actions listed below shall be taken:
l A.
Initiate an orderly shutdown and have reactor in the cold shutdown condition in 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
B.
Initiate an orderly load reduction and have reactor in " Hot Standby" within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.
- 3. Close isolation valves in system and comply with Snecification 3.5.
- 4. One trip system arranged in a two-out-of-two logic.
- 5. One trip *ystem arranged in a one-out-of-two twice logic.
- 6. The main steam line high flow is available only in the " Refuel", " Shutdown", and "Startup" modes.
- 7. This signal also automatically closes the *:chanical vacuum pump suction line isolation valves.
- 8. Channel shared by the Reactor Protection and Primary Coctninment Isolaticn Systems.
- 9. An alarm setting of 1.5 times normal background at rated power shall be e,tablished to alert the operator to abnormal radiation levels in the primary coolant.
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- 10. A key lock switch is provided to permit the bypass of this trip fune. tion to enable plant startup and shutdown when the condenser vacuum is greater than 12 inches 4fg absolute provided that both tur'oine stop and bypass valves are closed.
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VYNPS 3.2 (Continued)
High radiation monitors in the main steam line tunnel have been provided to detect gross fuel failure resulting from a control rod drop accident. This instrumentation causes closure of Group 1 valves, the only valves required to close for this accident. With the established setting of 3 times normal background and main steam line isolation valve c lo su re, fission product release is limited so that 10 CFR 100 limits are not exceeded for the control rod' drop accident and 10 CFR 20 limits are not exceeded for gross fuel failure during reactor operations. With an alarm getting of 1.5 times normal background, the operator is alerted to possible gross fuel f ailure or abnormal fission product releases from failed fuel due to transient reactor operation.
Pressure instrumentation is provided which trips when reactor pressure drops below 850 psig. A trip of this instrumentation results in closure of Group 1 isolation valves.
In the refuel, shutdown, and startup modes, this trip function is provided when main steam line flow exceeds 40% of rated capacity. This function is provided primarily to provide protection against a pressure regulator malfunction which would cause the control and/or bypass valves to open. With the trip set at 850 psig, inventory loss is limited so that fuel is not uncovered and peak clad temperatures are much less than 12950F; thus, there is no release of fission products other than those in the reactor wa ter.
Low condenser vaccuum has been added as a trip of the Crcup 1 isolation valves to prevent release of radioactive gases from the primary coolant through condenser. The set point of 12 inches of mercury absolute was selected to provide cufficient margin to' assure retention capability in the condenser when gas flow is stopped and sufficient margin below normal operating values.
The HPCI and/or RCIC high flow, steam supply pressure, and temperature instrumentation is provided to detect a break in the HPCI and/or RCIC piping. Tripping of this instrumentation results in actuation of HPCI and/or RCIC isolation valves; i.e., Group 6 valves. A time delay has been incorporated into the RCIC steam flow trip logic to prevent the system from inadvertantly isolating due to pressure spikes which may occur on startup.
The trip settings are such that core uncovering is prevented and fission product release is within limits.
The instrumentation which initiates ECCS action is arranged in a dual channel system. As for other vital instrumentation arranged in this f ashion, the specification preserves the effcetiveness of the system even during periods when maintenance or testing is being performed.
Permanently installed circuits ar.d equipment may be used to trip instrument channels.
In the non-fall safe systems which require energizing the circuitry, tripping an instrument channel may take the form of providing the required relay function by use of permanently installed circuits. This is accomplished in some cases by closing logic circuits with the aid of the permanently installed test jacks or other circuitry which would be installed for this purpose.
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VYNPS 4.3 LIMITING CONDITIONS FOR OPERATION 4.3 SURVCuaANCZ REQUIREMENTS l
5.
Control rods shall not be withdrawn for startup 5.
Prior to con ~ rol rod withdrawal for startup or or refueling unless at least two source range during ru.aeling, verification shall be made that channels have an observed count rate greater than at least two source range channels have en or equal to three counts per second.
- ohserved count. rate of at least three counts per seCOnd.
- 6. ' During operation with limiting control rod i
patterns eithcr:
6.
When a limiting control rod pattern exists, an 1
instrument functional test of the RBM shall be (a) Both RBM channels shall be operable; or performed prio: to withdrawal of the designated l-rod (s) and daily thereaf ter.
(b) Contr cod withdrawal shall be blocked; or 7.
.The scram discharge volume drain and vent valves (c) The operating pnwer level shall be limited shall be verified open:at least once per month.
so that the MCPR will -remain above the fuel These valves may be closed intermittently for cladding integrity safety limit assuming a tes ting under administra tive control.
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single error that resuls in complete withdrawal of any single operable control rod.
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VYNPS 5.
The Source Range Monitor (SRM) system has no scram functions.
It does provide the operator with a visual indication of neutron level. The ccnsequences of reactivity accidents are a. unction of the initial neutron flux..The requirement of at least three counts per second assures that any transient, should it occur, begins at or above the initial salue of 10-8 of rated power used in the anlyses of transients f rom cold conditions. One operable SRM channel is adequate to monitor the approach to criticality, therefore, two operable SRM's are specified for added conse rvatism.
l 6.
The Rod Block Monitor (RBM) is designed to automatically prevent fuel damage in the event of erroneous rod withdrawal f rom locations of high power density during high power level operation.
During reactor opera tion with certain limiting control rod patterns, the withdrawal of a designated single control rod could result in one or more fuel rods with MCPR less than the f uel cladding integrity safety limit. During use of such patterns, it is judged that testing of the RBM system prior to withdrawal of such rods will provide added assurance that improper withdrawal does not occur.
It is the responsibility of the Nuclear Engineer to identify these limiting patterns and the designated rods either when the patterns are initially established or as they develop due to the occurrence of inoperable control rods.
I 7.
Periodic verification that the Scram Discharge Volume (SDV) drain and vent valves are maintained in the open position provides assurante that the SDV will be available to accept the water displaced from the control rod l
drives in the event of a scram.
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