ML20002A930
| ML20002A930 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee  |
| Issue date: | 12/01/1980 |
| From: | VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | |
| Shared Package | |
| ML20002A927 | List: |
| References | |
| NUDOCS 8012090195 | |
| Download: ML20002A930 (12) | |
Text
_
l _
n\.
e d , r e e r l u n ,
b h o l s it t c a mo aa l ai n h al m l e r a . sl rc e a ren h n l e c fb h e ob e t e p
mun se v
o t
sh c i. f i t l e so r b el nl g yl h s cf r r a oa nf cat el s out uv s
ih t s i o nh l l t esf u e% o% a t p g o ef r0 e . l 0 i e eo rn eop b u3 h y c1 t r i u st m s t a G - - mio l o on l eo ns N
I me ah et t a
l r af l af e ch or l vt i o l
T rt li e h t al ec T c et h s e t ne va r E se vit r s ror u ue S v en mu as aeiu f t t s nq oe s v sl l o l i e M eb v ro aao i ea E va r) o cl eeul t r rv p
T e eSb s c vrt c ao S t C a l gc l n Y
l s e aC ee a at on wo S rh wE s vv vt s s a oi ec ( e l l ana ih l t a .
Y t n w h aa l of t .
T ai . omc vv ogp e n el g E w l l en rnue ns e noi F 7 e ti p% ti v is p i s s A w2 u ws oy5 o0 t 1 nt pl oaia l eo ml l ip m
S o1 f l l s s crrv a l ae0 G td 2 o ep et eel en5 N rs e r g8 et l t b u ti 8 I oah on n no ,o s f sl T t ec ti t . il i rr l mt I cl i cl sl b a b net nl m nas M a r a oae ru rewn i ao i ea I et n eceu uq uh oo T wpc ah r M sf at e Msl L R ae R el f Te 1
2 C D E F G H S
P d 3 e p Y t V a oe i t h dl t aee rvh n reti i l ed h rve t eot itb a aa e w s n s wet s ohhi d t c t nt u ,ii hl s e2 n s1 e s s h i enw va _
r hl _
ort e t o u _
ct sf acs eaed _
rel e r h _
T e ec _
I h ebi _
M th r I t t n L r oe enn Y vi e T e l h .
E nl l t e F eea r A h uhf o S Wf s oc 1
1 D U
codbf03DC CC
VYNPS 1.1 (cont'd)
- to assure the insertion times are adequate. The thermal power transient resulting when a scram ia accomplished other than by the expected scram signal (e.g., scram from neutron flux following closure of the main turbine stop valves) does not necessarilj s- ae fuel damage. However, for this specification a Safety Limit violation will be assumed when a scram is only accomplishco by means of a backup feature of the plant design. The concept of not approaching a Safety Limit provided scram
- onals are operable is supported by the extensive plant safety analysis.
The computer provided with Vermont Yankee has a sequence annunciation program which will indicate the sequence in which events such as scram, APRM trip initiation, pressure scram initiation, etc. occur. This program aisc indicates when the scram setpoint is cleared. This will provide information on how long a scram condition exists and thus provide some measure of the energy added during a transient.
D. Reactor Water Level (Shutdown Condition)
During periods when the reactor is shutdown, consideration must also be given to water level requirements due to the effect of decay heat. If reactor water level should drop below the top of the enriched fuel during this time, the ability to cool the core is reduced. This reduction in core cooling capability could lead to elevated cladding temperatures and clad perforation. The core can be cooled sufficiently should the water level be reduced to two-thirds the core height.
Establishment of the safety limit at 12 inches above the top of the enriched fuel provides adequate margin. This level will be continuously monitored.
12
VYNPS a
TABLE 3.1.1 REACTOR PROTECTION SYSTEM (SCRAM) INSTRUMENT REQUIREMENTS Modes in Which Minimum Numoer Required Conditions When Functions Must be Operating Instrument Minimum Conditions For Operating Chacanels Per Operation Are Not Trip Function Trip Settings Refuel (l) Startup Run Trip System (2) ' Satisfied (3)
- 1. Mode switch X X X 1 A in shutdown
- 2. Manual scram X X X 1 A
- 3. IRM High Flux -< 120/125 X X X(11) 2 A Loop X X X(11) 2 A
- 4. APRM High Flux <0.66W+54%(4) X 2 A or B (Flow bias)
High Flux <15% X X 2 A 2(5)
'(reduced) X A or D INOP Downscale >2/125 X 2 A or B
- 5. High Reactos- 11055 psig X X X 2 A Pressure 4
- 6. High Drywell 12.5 psig X X X 2 A Pressure
- 1. Reactor Low (6)>127.0 inches X X X 2 A [
Water Level ,
- 8. Scram Discharge <24 gallons X X X 2 A Volume liigh Level 19
~
VYNPS TABLE 3.1.1 N3TES
- 1. When the reactor is suberitical and the reactor water temperature is less than 2120F, only the following trip functions need to be operable:
a) mode switch in shutdown b) manual scram c) high fux IBM or high finx SRM in coincidence -
d) scram discharge volume high water level.
- 2. Whenever an ,strument system is found to be inoperable, the instrument system output relay shall be tripped immed ia tely. Except for MSIV & Turbine Stop Valve Position, this action shall result in tripping the trip system.
- 3. When the requirements in the column " Minimum Number of Operating Instrument Channels Per Trip System" cannot be met for one system, that system shall be tripped. If the requirements cannot be met for both trip systems, the appropriate actions listed below shall be taken:
A. Initiate insertion of operable rods and complete insertion of all operable rods within four hours.
B. Reduce power level to IRM range and place mode switch in the "Startup/ilet Standby" position within eight hours.
C. Reduce turbine lead and close main steamline isolation valves within eight hours.
D. Reduce reactor power to less than 30% of rated within eight hours.
- 4. "W" is percent rated drive flow where 100% rated drive flow is that flow equivalent to 48 x 106 lbs/hr core flow.
- 5. To be considered operable an APRM must have at least 2 LPRM inputs per level and at least a total of 13 LPRM inputs, except that channels A, C, D, and F may lose all LPRM inputs from the companion APRM Cabinet plus one additional LPRM input and still be considered operable.
- 6. The top of the enriched fuel has been designated as 0 inches and provides all common reference level for vessel water level instrumentation.
- 7. Channel sfi ared by the Reactor Protection and Primary Containment Isolation Systems.
- 8. An alarm setting of 1.5 times normal background at rated power shall be established to alert the operator to abnormal radiati,n levels in primary coolant.
21 1
VYNPS TABLE 3.2.1 EMERGENCY CORE COOLING SYSTEM ACTUATION INSTRUMENTATION Core Spray - A & B (Note 1)
Minimum Number of Operable Instrument Required Action When Minimum Channels per Trip Conditions for Operation are Syctem Trip Function Trip Level Setting not Satisfied 2 High Drywell Presure 12.5 psig Note 2 2 Low-Low Reactor V'wsel Water 182.5" above top Note 2 Level of enriched fuel 1 Low Rer_cor Pressure #1 1300 psig Note 2 2 Low Reactor Pressure #2 1300 psig Note 2 1 Time Delay (14A-K16A&B) 110 seconds Note 2 2 Pump 14-1A, Discharge Pressure 1100 psig Note 5 1- Auxiliary Power Monitor --
Note 5 1 Pump Bus Power Monitor --
Note 5 1 High Sparger Pressure 15 psid Note 5 1 Trip System Logic --
Note 5 35
VYNPS .
TABLE 3.2.1 (CONT)
EMERGENCY CORE COOLING SYSTEM ACTUATION INSTRUMENTATION Low Pressure Coolant Injection System A & B (Note 1) '
Minimum Number of Operable Instrument Required Action When Minimum Conditions for Operation are Channels per Trip Trip Function Trip Level Setting not Satisfied System 1 Low Reactor Pressure #1 (water 300 1 p 1 350 psig Note 2 level permissive 2 iligh Drywell Pressure #1 12.5 psig Note 2 2 Low-Low Reactor Vessel Water 182.5" above top of Note 2 f.evel enriched fuel i 1 Time Delay (10A-K51A1 T 0 sec. Note 5 1 Reactor Vessel Shroud Level 1 2/3 core height Note 5 1 Time Delay (10A-K72A&B) 1 60 sec. Note 5 1 Time Delay (10A-K50A&B) 1 5 sec. Note 5 1 Low Reactor Pressure #2 100 1 p i 150 psi'g Note 2 (shutdown cooling permissive 2 per pump RilR Pump A & C Discharge Pressure 1100 psig Note 5 2 liigh Drywell Pressure #2 12.5 psig Note 7 36
VYNPS TABLE 3.2.1 (CONT)
EMERGENCY CORE COOLING SYSTEM ACTUATION INSTRUM.iNTATION HIGH PRESSURE COOLANT INJECTION SYSTEM Minimum Number of Operable Instrument Required Action When Minimum Channels per Trip Conditions.for Operation are System Trip Function Trip Level Setting not Satisfied 2 (Note 3) Low-Lou Reactor 'lesse.f Same as LPCI Note 5 Water Level 2 (Note 4) Low Condensate Storage > (-)2 inches Note 5 Tank Water Level 2 (Note 3) High Drywell Pressure Same as LPCI Note 5 2 (Note 4) High Suppression Chamber 12 inches Note 5 Water Level 1 (Note 3) Bus Power Monitor --
Note 5 1 (Note 4) Trip System Logic --
Note 5 2 (Note 7) High Reactor Vessel 1177 inches above top Note 5 Water Level of enriched fuel 38
UYNPS TABLE 3.2.1 (CONT)
EMERGENCY CORE COOLING SYSTEM ACTUATION INSTRUMENTATION Recirculation Pump Trip - A & B (Note 1) -
Minimum Number of Operable Instrument Required Action When Minimum Channels per Trip Conditions for Operation are System Trip Function Trip Level Setting not Satisfied 2 Low-Low Reactor Vessel > 82.5" above top of Note 2 Water Level enriched fuel 2 liigh Reactor Pressure f_1150 psig Note 2 2 Tin.a Delays $10 sec. Note 2 1 Trip System Logic --
Note 2 39a
VYNPS TABLE 3.2.2 PRIMARY CONTAINMENT ISOLATION INSTRUMENTATION Minimum Number of Operable Instrument Required Action When Minimum Channels per Trip Conditions for Operation are System Trip Function Trip Setting not Satisfied (Note 2) 2 Low-Low Reactor Vessel 182.5" above the A Water Level top of enriched fuel 2 of 4 in each of High Main Steam Line 12120F B 2 channels Area Temperature 2/steamline liigh Main Steam Line Flow 1120% of rated flow B 2/(Note 1) Low Main Steam Line Pressure 1850 psig B 2/(Note 5) liigh Main Steam Line Flow 140% of rated flow B 2
- ' Low Reactor Vessel Same as Reactor Water Level Protection System A 2 liigh Main Steam Line 1 3 X background at Radiation (7) (8) rated power (9) B 2 liigh Drywell Pressure Same as Reactor Protaction System A 2/(Note 10) Condenser Low Vacuum 1 12" Hg absolute A
! Trip System Logic --
A 41
VYNPS ,,
TABLE 3.2.2 (CONT'D)
HICH PRESSURE COOLANT INJECTION SYSTEM ISOLATION INSTRUMENTATION Minimum Number of Operable Instrument Required Action When Minimum Channels per Trip Conditions for Operation are System Trip Function Trip Setting not Satisfied 2 (Note 4) High Reactor Water Level 1177" above the top of enriched fuel Note 3 2 per set of 4 High Steam Line Space 12120F Note 3 d
Temperature 1 High Steam Line d/p 1195 inches of water Note 3 (Steam Line Break) ,
4 (Note 5) Low HPCI Steam Supply 2.70 psig Note 3 Fressure 0
2 Main Steam Line Tunnel 1212 F Note 3 Temperature 1 Time Delay (23A-K48 23A-K49 1 Bus Power Monitor - --
1 Trip System Logic -- --
4 42.
VYNPS - -
Bases 3.2 PROTECTIVE INSTRUMENTATION In addition to reactor protection instrumentation which initiates a reactor scram, station protective instrumentation has been provided which initiates action to mitigate the consequences of accidents which are beyond the reactor operator's ability to control, or terminate a single operator error before ib results in serious consequences. This set of Specifications provides the limiting conditions of operation for the primary system isolation function and initiation of the core standby cooling and standby gas treatment systems. The obiectives of the Specifications are (i) to assure the effectivenes of any component of such systems even during perieJs when portions of such systems are out of service for maintenance, testing, or calibration, and (ii) to pre;cribe the trip settings required to assure adequate performance. This set of Specifications also provides the limiting conditions of operation for the control rod block system and surveillance instrumentation.
Isolation valves (Note 1) are installed in those lines that penetrate the primary containment and must be isolated during a loss-of-coolant accident so that the radiation dose limits are not exceeded during an accident condition.
Actuation of these valves is initiated by protective instrumentation shown in Table 3.2.2 which senses the conditions for which isolation is required. Such instrumentation must be available whenever primary containment integrity is required. The objective is to isolate the primary containment so that the limits of 10 CFR 100 are not exceeded during an accident. The objective of the low turbine condenser vacuum trip is to minimize the radioactive effluent releases to as low as practical in case of a main condenser failure. Subsequent releases would continue until operator action was taken to isolate the main condenser unless the main steam line isolation valves were closed automatically on low condenser vacuum. The manual bypass is required to permit initial startup of the reactor during low power operation.
The instrumentaion which initiates primary system isolation is connected in a dual channel arrangement. Thus, the discussion given in the bases for Specification 3.1 is applicable here.
The low reactor water level instrumentation is set to trip when reactor water level is 127" above the top of the enriched fuel. This trip initiates closure of Group 2 and 3 primary containment isolation valves. For a trip setting of 127" above the top of the enriched fuel, the valves will be closed before perforation of the clad occurs even for the maximum break and, therefore, the setting is adequate.
The top of the enriched fuel (351.5" from vessel bottom) is designated as a common reference level for all reactor water level instrumentation. The intent is to minimize the potential for operator confusion which may result from different scale references.
Note 1 - Isolation valves are grouped as listed in Table 3.7.1.
62
VYNPS 3.2 (cont'd)
The low-low reactor water level instrumentation is set to trip when reactor water level is 82.5" H O indicated 2 on the reactor water level instrumentation above the top of the enriched fuel. This trip initiates closure of the Group 1 primary containment isolation valves and also activates the ECCS and starts the standby diesel generator system.-
This trip setting level was chosen to be low enough to prevent spurius operation but high enough to initiate ECCS operation and primary system isolation so that no melting of the fuel cladding will occur and so that post-accident cooling can be accomplished and the limits of 10 CFR 100 will not be violated. For the complete circumferential break of a 28-inch recirculation line and with the trip setting given above, ECCS initiation end primary system isolation are initiated in time to meet the above criteria. The instrumentation also covers the full range of spectrum of breaks and meets the above criteria.
The high drywell pressure instrumentation is a backup to the water level instrumentation and in addition to initiating ECCS it causes isolation of Group 2, 3, and 4 isolation valves. For the complete circumferential break discussed above, this instrumentation will initiate ECCS operation at about the same tiae c, the low-low water level instrumentation, thus the results given above are applicable cere alco. Group 2 isolation valves include the drywell vent, purge, and sump isolation valves. High drywell pressure activates only these valves because high drywell pressure could occur as the result of non-safety related causes such as not purging the drywell air during startup.
Total system isolation is not uesirable for these conditions and only the valves in Group 2 are required to close.
The wa ter level instrumentation initiates protection for the full spectrum of loss-of coolant accidents and causes a trip of all primary system isolation valves.
Venturis are provided in the main steam lines as a means of measuring steam flow and also limiting the loss of mass inventory from the vessel during a steam line break accident. In addition to monitoring steam flow, instrumentation is provided which causes a trip of Group 1 isolation valves. The primary function of the instrumentation is to detect a break in the main steam line, thus only Group 1 valves are closed. For the worst case accident, main steam line break outside the drywell, this trip setting of 120 percent of rated steam flow in conjunction with the flow limiters and main steam line valve closure limit the mass inventory loss such that fuel is not uncovered, fuel temperatures remain less than 1295 F and release of radioactivity to the environs is well below 10 CFR 100.
Temperature monitoring instrumentation is provided in the main steam line tunnel to detect leaks in this area. Trips are provided en this instrumentation and when exceeded cause closure of Group 1 isolation valves. Its setting of ambient plus 950F is low enough to detect leaks of the order of 5 to 10 gpm; thus, it is capable of covering the en tire spectrum o f breaks. For large breaks, it is a backup to high steam flow instrumentation discussed above, and for small breaks with the resultant small re: ease of radioactivity, gives isolation before the limits of 10 CFR 100 are exceeded.
63 s
_ - . _ _ _ _ . - - _ _ _ - _ _ _ . - _ -