ML17258A315
| ML17258A315 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 11/03/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17258A314 | List: |
| References | |
| NUDOCS 8111170497 | |
| Download: ML17258A315 (7) | |
Text
gSWI AECIIE UNITED STATES I
E, NUC R REGULATORY COMMISSION WASHINGTON, D. C. 20555 r+
+a*++
KATY EYALUATION BY'HE'OFFICE OF NUCLEAR REACTOR REGULATION PROPOSED SPENT FUEL COOLING SYSTEM ROCHESTER GAS AND ELECTRIC CORPORATION R. E.
GINNA NUCLEAR POWER PLANT DOCKET NO. 50-244 1.0 INTRODUCTIOH h
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. By letters dated February 13, 1980 and June 9, 1981, the Rochester Gas and Electric.Corporation (RG&E) submitted a request for approval of modifications to increase the heat removal capacity of the spent fuel pool cooling system (SFPCS) at the R.
E. Ginna Nuclear Power Plant.
This-application is in accordance with the 1976 license amendment which permitted R.
E. Ginna.to re-rack the spent fuel storage pool; increasing the storage capacity from 210 fuel assemblies to 595 fuel assemblies without a concurrent increase in the capacity of the spent fuel pool cooling system; The decay heat resulting from the fuel stored in the pool at the time of the 1 976 1 icensing action was si~i ficantly less (92 fuel assemblies) than the capability of the existing SFPCS.
Therefore it was stipulate'd that RGSE commit to submitting the SFPCS modification in a timely manner at'ome future date before the pool's heat load exceeds the capacity of the existing SFPCS.
Without degrading the performance of the existing
- SFPCS, RGEE proposed to install an additional parallel cooling loop designed to seismic Category'I criteria.
Based on the stated decay times, before the fuel is moyed into the pool, the heat removal capability of the new 1005 capacity spent fuel pool cooling loop (16 x 106
" at a pool temperature of 150'F) is capable of removing the total "R accumulated decay heat from dis,charged fuel assembl.ies up through the year 2009 and a full core.discharge in year 2010 (1360 fuel assemblies total).
In addition a 100/ capacity non-seismic Category I backup SFPCS is provided..
It will consist of the existing SFPCS and a skid-mounted cooling system.
Each is c'apable of removing 7.93 x 106 BTU/HR at a pool temperature of 150'F.
The spent fuel pool contains 255,102 gallons of water.
'iiii70497 Biii03 I PDR ADOCK 05000244 PDR
2.0 DECAY HEAT 3.0 The June 9, 1981 submittal presents the res'ults of an RGEE analysis of the Ginna spent fuel pool's future decay heat load assuming a plant life of 40 years (year 2009) including the existing stored spent fuel.'(231 fuel" assemblies) and all future discharged fuel.
Typically a-normal annual discharge ranges between 28 and 32 fuel assemblies.
The analysis con-
'ervatively assumes that 36 fuel assemblies are discharged instantaneously-to the pool'ollowing 100 hour0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> cooling in the reactor vessel.
The maximum total'ccumulated heat load incrementally increases from 7.07 x 106 BTU/HR
'in 1'981 to 9.96 x 106 BTU/HR in the year 2010.
P J
~I Assuming a.full core discharge were to occur at each refueling cycle, RG&E states they= will maintain the maximum total accumulated decay heat load in the pool slightly below the rated capacity of the new SFPCS (16 x 106 BTU/HR when the pool water temperature is allowed to rise to 1,50'F) by incrementally increasing the cooldown time in the reactor vessel from 8 days in the 'year 1981 to 14 days in the'.year 2010.
Using the stipulated cooldown times, we have checked the calculated dec'ay heat values given in the June,9;
.1981 submittal and.find them. to be consistent with NRC Branch Technical Position APCSB 9-2 and, therefore, Whey are acceptabl.e.
NEW SPENT FUEL POOL COOLING SYSTEM~~
The proposed spent fuel pool cooling system (SFPCS) will consist of a seismic Category I additional cooling loop in parallel with the existing SFPCS.
It will be designed and i'nstalled such.that it will not degrade the performance of the existing SFPCS or service water system.
The -.added cooling loop consists
'of one shell and U-tube type heat exchange'r, one.horizontal/centrifugal stainless.
steel pump, plus the stainless steel piping, valves and associated controls.
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The performance of the added
- SFPCS, under the described conditions, is presented below:
Desi n Heat Load Conditions I ~
- Initial decay heat, Btu/hr.
Maximum pool temperature,
'F SFP heat up rate, 'F/hr.
(assufnes noeecoollng)
Full Core Discharoe 16 x 10 6 150 7.7 Oi h
7.6 x 106 120 3;7 Service Water Requirements SW temperature,
'F Max.
SW temp; increase,
'F SW flow, gpm (approx.)
80 20
.1600 80 15 1000
The controls for both the new and existing pumps are from local control
- stations located near -the pumps.
Mechanical interlocks will be provided to prevent the simultaneous operation of the new and existing 'cooling
.systems.
The two existing spent fuel pool suction lines will be piped to a
common header which supplies pool water to the install'ed'FPCS pumps..
The piping will be designed to assure adequate NPSH at the pumps and flow
-for-the removal of the design heat loads.,
Check va]ves in:the new and
=existing pump discharge lines will,prevent back flow.;.
.Local pressure, temperature and flow.,instrumentation. will be provided.in
.the'new cooling loop for testing and monitoring its performance.,'he
'fl'ow indicating device will. 'alert 'the 'control room in. the event low flbw
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or.
a pump trip occurs.
An additional pool water level switch will,be":
installed..'n the event the low;leve3.is reached the. pool'.water-level
..siiitch.will trip the pump.
,The pum'p.'.will be powered, by essential bus 816.
It'will be shed, in.the'vent of a safety.,injection signal.,
After. abo'ut one hour into,the safety, injection. event the pump can be. manually started
.a'nd operate'd on diesel generatoi 1B.
'(
To the, extent practical ele'ctrical'.separation of the.new,and. existin'g'SFPCS
'motors and controls will.be in accordance with IEEE 384.
Radiation detectors, al'arms and recorders will detect radioactivity in'the service water should' tube'eak develop in one of the heat exchangers.
Based on our review we find the new SFPCS meets our criteria and therefore is acceptable.
4.0 BACKUP COOLING SYSTEM The existing SFPCS and a skid mounted unit, capable of operating in parallel comprise the 100Ã capacity backup cooling system.
RGRE states that the backup cooling system will be in place and available before a full core discharge takes place.
Service water from loop A will provide cooling for the backup cooling system while service water from loop B will provide cooling for the new SFPCS loop.
The following subsections describe the components of this backup cooling system.
4.1 EXISTING COOLING SYSTEM The'xisting SFPCS consists of a horizontal/centrifugal stainless steel pump and a shell and U-tube type heat exchanger.
The loop will be powered by essential bus 814.
A safety injection signal will cause the pump to be shed from the bus.
At the termination of safety injection the pump can be started and powered on diesel generator 1A.
Upon coincident loss of offsite power and safeguard actuation signals the existing SFPCS will be isolated from the service water system.
Handwheels are provided for manual operation.
The existing cooling system is rated as follows.:
Full Core Dischar e
Maximum Heat Removal Rated Conditions
, Normal
~Dischar s
Heat Removal Capacity
- 9.3 x 10 BTU/HR 7.93 x 10 BTU/HR 6
80'F '0'F Service Water Temperature In Service Mater Temperature Out' Service Water Temperature Differential 100'F 20oF*
Pool Mater Temperature 150'F 150'F r"
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- Environmental guidelines require the lake water'differential temperature not to exceed 20'F.
This requirement is neither an NRC or nuclear safety requirement.
Therefore for the maximum heat removal mode, this 20'F limitation on the SFPCS is relaxed, considering that the water discharge from the SFPCS will mix with the discharge from other equi.pment and ensure that the overall plant disch@ge differential temperature of. 20'F is not exceeded.
x 106 BTU HR 80'F l
100'F 20'.F 120'F 4.2 4 a3 Sl'ID-t~iOUNTED COOLING SYSTEM The manually operated skid-mounted cooling system, consisting of a pump and heat exchanger, will be powered by a non-safety power source.
When operating in parallel with the existing SFPCS it is rated at 7.93 x 106 BTU/HR with a pool temperature of 150'F, service water inlet temperature of 80'F and service water. outlet temperature of 100'F.
USE OF EXISTING COOLING SYSTEMS TO AUGMENT THE CAPACITY OF THE NEW SFPCS The Ginna Final Safety Analysi s Report (FSAR) indi cates that the operational limit for the pool water temperature during normal refuelings is 120'F.
The total accumulated decay heat lo'ad, assuming normal discharges, incrementally increases from 7.07 x 106 BTU/HR to 9.96 x 106 BTU/HR at the end of plant life.
Once"tiie Pal'ue exceeds 7.6 x 106 BTU/HR (about year 1985) the new SFPCS will not be able to maintain the pool water temperature at 120'F.',
For a matter of a few days the decay heat would cause the pool water temperature to rise to some value greater than 120'F.
However the heat removal capability of the system will also increase as the pool water temperature increases.
'I Whereas the 120'F temperature is not an NRC or safety requirement,.
RGSE indicates that for operator comfort during refueling they plan to maintain the pool water temperature around 120',F by placing one of the backup,
. cooling systems in operation for a few days, until the decay he'at has decayed below the rating of the new spent, fuel pool cooling system (7.6 x 106 BTU/HR).
We find this acceptable.
. The Ginna Technical Specifications indicate that due to,structural integrity considerations the pool water temperature is not to exceed.
180 F; Therefore, in'rder to provide time sufficient to take corrective
, act'ion, the pool temperature is not to exceed 150'F for all modes of.;
operation including a full core discharge.
Our calculations show that" in -the unlikely event that the new SFPCS should become inoperative when the pool water 'temperature is 150'F and the. heat load is 16 x 106 BTU/HR, the pool water'temperature would begin to rise at a rate of 7.5'F per houp.
In approximately 45 minutes the existing SFPCS could be placed in operation at which=time the pool water-temperature would be 156'F.
At this time the increase in pool water temperature would drop to approximately' 3'F/hr.
.Therefore an additional.8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> are available, to repair the new SFP cooling loop or to activate the skid mounted unit, before the pool water temperature reaches 1 80'F.
- RGSE, indicates that -appro~imately
- 3. hours are required to place the'kid mounted unit in.parallel operation'with"the existing SFPCS.
In this time the pool water temperature would rise '9'F and the temperature would be 165'F;
.We conclude that adequate time and cooling systems are available to prevent the pool water from reaching 180'F and therefore the'new SFPCS and backup'ystems are acceptable.
'.0'AKEUP SYSTEM The normal makeup water source is the Refueling Water Storage Tank.
It contains a minimum of 230,000 gallons of borated water.
The maximum makeup rate of 6') gpm can be made available in less than 15 minutes.
The following alternate makeup sources and makeup rates are possible in the indicated times:
a)
Primary Water Tr'eatment Plant, 120 gpm in 15 miriutes b)
Reactor Makeup Water. Tank or the Monitor Tanks, 40gpm in 45 minutes and c)
Fire System which can be initiated in less than one hour.
, Makeup'water'may be "necessary. in the event of a leak in the
- SFPCS, the pool or in the unlikely event that pool boiling should occur.
Whereas boiling is highly unlikely the makeup rate from the above sources exceeds the boiloff rate of 33 gpm and therefore these sources are acceptable in this regard.
The pool water leakage is collected by channels which direct it to a container.
The level. in this container is checked 'twice per shift.
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r Past operating experience has shown the leakage to be very small.
In addition, leak detection is possible should the pool level drop 20 inches below the top of the spent fuel pool.
This would activate the spent fuel pool low level alarm on the main control board.
P We have reviewed the above information and conclude that adequate measures have been provided to detect leakage and.to provide makeup water.. The design is therefore acceptable.
- 6. 0 CONCLUS ION Based on our,review,.we conclude that the proposed SFPCS modification "is acceptable and that this system, and the existing backup systems, will maintain pool temperature below that at which the pool was structurally analyzed and found to be acceptable.
Date:
November 3,
1981
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