ML20211A495
| ML20211A495 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 09/26/1986 |
| From: | NORTHEAST NUCLEAR ENERGY CO. |
| To: | |
| Shared Package | |
| ML20211A486 | List: |
| References | |
| TAC-61560, NUDOCS 8610150175 | |
| Download: ML20211A495 (12) | |
Text
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REFUELING OPERATIONS DECAY TIME LIMITING CONDITION FOR OPERATION 3.9.3.1 The reactor shall be subcritical for a minimum of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> prior to movement of irradiated fuel in the reactor pressure vessel.
APPLICABILITY: MODE 6.
ACTION:
With the reactor subcritical for less than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, suspend all operations involving movement of irradiated fuel in the reactor pressure vessel.
SURVEILLANCE REQUIREMENTS 4.9.3.1 The reactor shall be determined to have been subcritical for at least l 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> by verification of the date and time of subcriticality prior to movement of irradiated fuel in the reactor pressure vessel.
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8610150175 860926 '
PDR ADOCK 05000336 P PDR MILLSTONE - UNIT 2 3/49-3
REFUELING OPERATIONS' DECAY TIME LIMITING CONDITION FOR OPERATION 3.9.3.2 At least two trains of the spent fuel pool cooling system shall be OPERABLE.
APPLICABILITY: MODE 5 and 6 with the most recent 1/3 core offload
- decayed less than 504 hours0.00583 days <br />0.14 hours <br />8.333333e-4 weeks <br />1.91772e-4 months <br /> from subcriticality. This specification is not applicable if Shutdown Cooling is being used to cool the spent fuel pool.
ACTION:
With the above conditions not satisfied;
- a. Immediately initiate actions to restore both trains of spent fuel pool cooling, and
- b. Within one hour, suspend all fuel movement in the spent fuel pool, and i
- c. With one hour, isolate the spent fuel pool cleanup demineralizers.
4 SURVEILLANCE REQUIREMENTS 4.9.3.2 Within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> prior to fuel movement into the spent fuel pool, and every 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> thereafter while this specification is applicable, verify that two trains of the spent fuel cooling system are OPERABLE.
For the purposes of this specification, the most recent 1/3 core offload is defined as the fuel bundles discharged at the end cf the most recent fuel cycle. This specification does not apply to partial mid-cycle discharges resulting from defective or damaged fuel if the total decay heat load on the spent fuel pool cooling system resulting from such a discharge is less than the total decay heat load of the spent fuel pool at 504 hours0.00583 days <br />0.14 hours <br />8.333333e-4 weeks <br />1.91772e-4 months <br /> after subcriticality of the most recent 1/3 core offload.
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REFUELING OPERATIONS' DECAY TIME LIMITING CONDITION FOR OPERATION 3.9.3.3 The reactor shall be maintained in MODE 5 or 6 until the most recent 1/3 core offload
- in the spent fuel pool has decayed for greater than 504 hours0.00583 days <br />0.14 hours <br />8.333333e-4 weeks <br />1.91772e-4 months <br /> from subcriticality.
APPLICABILITY: MODE 5 and 6 with the most recent 1/3 core offload
- decayed less than 504 hours0.00583 days <br />0.14 hours <br />8.333333e-4 weeks <br />1.91772e-4 months <br /> from subcriticality.
ACTION:
With the above conditions not satisfied, immediately initiate actions to restore the reactor to MODE 5 or 6.
SURVEILLANCE REQUIREMENTS 4.9.3.3 Within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> prior to entry into MODE 4, verify that the most recent 1/3 core offload
- has decayed for greater than 504 hours0.00583 days <br />0.14 hours <br />8.333333e-4 weeks <br />1.91772e-4 months <br /> from subcriticality.
- For the purposes of this specification, the most recent 1/3 core offload is defined as the fuel bundles discharged at the end of the most recent fuel cycle. This specification does not apply to partial mid-cycle discharges resulting from defective or damaged fuel if the total decay heat load on the spent fuel pool cooling system resulting from such a discharge is less -
than the total decay heat load of the spent fuel pool at 504 hours0.00583 days <br />0.14 hours <br />8.333333e-4 weeks <br />1.91772e-4 months <br /> af ter subcriticality of the most recent 1/3 core offload.
i MILLSTONE - UNIT 2 3/4 9-3h
3/4.9 REFUELING OPERATIONS BASES 3/4.9.1 BORON CONCENTRATION he limitations on reactivity conditions during REFUELING ensure that: 1) the reactor will remain subcritical during CORE ALTERATIONS, and 2) a uniform boron concentration is maintained for reactivity control in the water volume having direct access to the reactor vessel.
%ese limitations are consistent with the initial conditions assumed for the boron dilution incident in the accident analyses.
3/4.9.2 INSTRUMENIATION The OPERABILITY of the source range neutron flux monitors ensures that redundant monitoring capability is available to detect changes in the reactivity condition of the core.
3/4.9.3 DECAY TIME The minimum requirement for reactor subcriticality prior to movement of irradiated fuel ensures that sufficient time has elapsed to allow the radioactive decay of the short lived fission products. This decay time is consistent with the assumptions used in the accident analyses.
We requirement for two trains of spent fuel pool cooling to be OPERABLE for 504 hours0.00583 days <br />0.14 hours <br />8.333333e-4 weeks <br />1.91772e-4 months <br /> after subcriticality for the most recently discharged 1/3 core ensures that high water temperature will not degrade resin in the spent fuel pool demineralizers and that the temperature and humidity above the pool are compatible with personnel comfort and safety requirements. We shutdown cooling (SDC) system is a high capacity system. One train of the SDC is sufficient to cool both the core and the spent fuel pool should a failure occur in the spent fuel pool cooling system.
We requirement for the reactor to remain in MODE 5 or 6 until the most recent 1/3 core offload has decayed 504 hours0.00583 days <br />0.14 hours <br />8.333333e-4 weeks <br />1.91772e-4 months <br /> ensures that alternate cooling is available during this time to cool the spent fuel pool should a failure occur in one train of the spent fuel p;ol cooling system, s 3/4.9.4 CCNTAINMENT PENETRATIONS he requirements on containment penetration closure and OPERABILITY ensure that a release of radioactive material within containment will be restricted from leakage to the environment. %e OPERABILITY and closure restrictions are sufficient to restrict radioactive material release from a fuel element rupture based upon the lack of containment pressurization potential while in the REFUELING MODE. ,
MILLS'IONE - UNIT 2 B 3/4 9-1
REFUELING OPERATIONS BASES 3/4.9.5 COMMUNICATIONS
'Ihe requirement for communications capability ensures that refueling station personnel can be promptly informed of significant changes in the facility status or core reactivity condition during fuel or CEA movement within the reactor pressure vessel.
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MILLS'IONE - UNIT 2 B 3/4 9-la f
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l Docket No. 50-336 B12267
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1 ATTACHMENT 2 Millstone Nuclear Power Station, Unit No; 2
- Safety Evaluation and No Significant Hazards Consideration Determination J
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I. Spent Fuel Pool Cooling System Safety Evaluation Proposed Technical Specification 3.9.3.2 requires that when in Mode 5 or 6 and the most recent 1/3 core offload having decayed less than 504 hours0.00583 days <br />0.14 hours <br />8.333333e-4 weeks <br />1.91772e-4 months <br />, both spent fuel pool cooling trains shall be OPERABLE. This proposed specifica-tion is required because the spent fuel pool cooling system does not possess the cooling capacity required by the NRC for a single active failure. During the first 504 hours0.00583 days <br />0.14 hours <br />8.333333e-4 weeks <br />1.91772e-4 months <br /> after subcriticality with all available storage locations occupied with spent fuel and with a fresh 1/3 core offload, both trains of spent fuel pool cooling are required to maintain the spent fuel pool water at a temperature which is compatible with the spent fuel pool cleanup system demineralizer resins and to ensure personnel exposure to elevated temperatures and humidity ova the pool resulting from elevated water temperature does not pose a personnel safety hazard. Should one train become inoperable, the proposed specification action statement requires suspension of all fuel movement in the spent fuel pool and isolation of the demineralizers within one hour if both trains have not been restored. Also, Operating Procedure 2305 requires isolation of the demineralizers if inlet temperature exceeds 1400F.-
This proposed specification is not applicable when the spent fuel poolis being cooled by the Shutdown Cooling System. The Shutdown Cooling System is a high-capacity cooling system which is designed to maintain a full core at 1300F at 275 hours0.00318 days <br />0.0764 hours <br />4.546958e-4 weeks <br />1.046375e-4 months <br /> after shutdown. Because of this large capacity, it can easily maintain the spent fuel pool at a stable, acceptable temperature (less than 1400F) at several days following subcriticality and 1/3 core offload.
The worst case single failure that could occur within 504 hours0.00583 days <br />0.14 hours <br />8.333333e-4 weeks <br />1.91772e-4 months <br /> after subcriticality while in two train operation would be the failure of the cooling
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water supply to a spent fuel pool heat exchanger. With half the fluid in the spent fuel pool cooling system flowing through an idle heat exchanger, the temperature of the pool would peak out in excess of 1700F. However, this is not a realistic failure since operator action can be taken within several hours to isolate the idle heat exchanger. With two spent fuel pool cooling pumps delivering flow to one spent fuel pool heat exchanger, the peak pool
- l. temperature will be approximately 1570F.
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l The other single failure evaluated was the mechanical failure of a single spent fuel pool cooling pump. This failure is less limiting because with
- one pump delivering flow through two heat exchangers, the spent fuel pool i temperature will peak at approximately 1450F.
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After the most recent 1/3 core offload has decayed greater than 504 hours0.00583 days <br />0.14 hours <br />8.333333e-4 weeks <br />1.91772e-4 months <br />, the spent fuel pool cooling system can tolerate. a single failure and still maintain acceptable temperatures. According to CE calculations,490 hours0.00567 days <br />0.136 hours <br />8.101852e-4 weeks <br />1.86445e-4 months <br /> are required to reach this point. Preliminary independent calculations by the NRC Staff concluded that 504 hours0.00583 days <br />0.14 hours <br />8.333333e-4 weeks <br />1.91772e-4 months <br /> would be required before one train of spent fuel pool cooling could maintain acceptable temperatures. Since both calculated times are close, the more conservative 504 hours0.00583 days <br />0.14 hours <br />8.333333e-4 weeks <br />1.91772e-4 months <br />.was chosen as the basis for this specification.
Proposed Technical Specification 3/4.9.3.3 prevents the reactor from enter-Ing Mode 4 until 504 hours0.00583 days <br />0.14 hours <br />8.333333e-4 weeks <br />1.91772e-4 months <br /> of decay time have elapsed on the most recent 1/3 core offload. This ensures that alternate cooling is available to cool the spent fuel pool if required due to a failure in the spent fuel pool cooling system. Although' shutdown cooling is not required by technical specifica-1 tions in Mode 5, it is operationally required to maintain the unit in Mode 5.
The footnote in the proposed Technical Specifications permits a partial mid-cycle fuel discharge. This is valid as'long as the partial discharge would result in a lower decay heat load than would exist following a normal 1/3 core refueling offload with 504 hours0.00583 days <br />0.14 hours <br />8.333333e-4 weeks <br />1.91772e-4 months <br /> of decay.
The proposed change to Technical Specification 3.9.3 to be renumbered
! 3.9.3.1 is required for consistency with the proposed new Technical Specifica-tions 3.9.3.2 and 3.9.3.3. The proposed change to Technical Specification Bases 3/4.9.3 requires the addition of a new page numbered B 3/4 9-la to '
provide sufficient space for the expanded Bases.
II. Spent Fuel Pool Mechanical Safety Evaluation 4
The proposed technical specifications would establish an operability require-4- ment for both trains of spent fuel pool cooling together with a decay time limit of 504 hours0.00583 days <br />0.14 hours <br />8.333333e-4 weeks <br />1.91772e-4 months <br /> to restrict startup after a refueling 1/3 core offload. This will ensure that the spent fuel pool and spent fuel storage racks are i maintained within the design criteria for Millstone Unit No. 2 in the event of a single active failure of the spent fuel pool cooling system; that is, the spent
, fuel rack structures are maintained below 2350F and the peak pool tempera-I ture is maintained below 2120F.
The following tables delineate the heat loads, operating temperature 9 and thermal hydraulic criteria of the spent fuel pool for which the racks have i
been analyzed, qualified and licensed.
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Table I SPENT FUEL POOL COOLING SYSTEM HEAT LOADS AND OPERATING TEMPERATURES Normal Maximum Heat Load: 15.2 X 106 BTU /hr(I)
Abnormal Maximum Heat Load: 37.8 X 106 BTU /hr(2)
OPERATING CONDITION POOL TEMPERATURES Design Basis Design Calculated Normal Mr.ximum 1200F 1310F(3)*
Abnormal Maximum 1500F 1200F(4)
Single Active Failure of a SFP Cooling Train Normal Maximum 2120F 1780F**
Abnormal Maximum 2120F 1850F Total Loss of Forced Pool Cooling Normal Maximum 2120F 9 3/4 hrs. to boiling Abnormal Maximum 2120F 4 hrs, to boiling (1) This heat load is predicted for normal refueling with the most recently unloaded one-third core having decayed for 150 hours0.00174 days <br />0.0417 hours <br />2.480159e-4 weeks <br />5.7075e-5 months <br />. After 12 more days, the decay heat load will be less than 11.3 X 106 BTU /hr.
(2) This heat load is predicted for spent fuel in the pool with the entire core offloaded.
(3) This temperature is a function of using only the Spent Fuel Pool cooling heat exchangers.
(4) This temperature value is a function of using one train of the Shutdown Cooling Heat Exchangers in addition to Spent Fuel Pool Heat Exchangers.
The consequences of exceeding the design value were previously addressed and found to be acceptable in a letter dated July 24,1985, 3.F. Opeka to E.3.
Butcher, " Millstone Nuclear Power Station, Unit No. 2 Proposed Change toTechnical Specifications Modifications to Spent Fuel Storage Pool," Docket No. 50-336, Section 5.2.1 and a letter dated May 21,1986,3.F. Opeka to A.C.
- Thadani, " Millstone Nuclear Power Station, Unit No. 2 Proposed Change to Technical Specifications Storage of Consolidated Spent Fuel," Docket No. 50-336, Sections 5.2.1 and 5.2.2.
- The 1780F value is representative of the failure of Valve 2-RB-8.lA (or IB) controlling RBCCW flow to the heat exchanger. The resulting temperature assumes no corrective action to realign flow and isolate the subject heat exchanger.
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TABLE II THERMAL HYDRAULIC DESIGN PARAMETERS Number Assemblies Normal Reload 1/3 core Minimum Decay Time One Assembly 3 days Minimum Decay Time Full Core 6 days Minimum Cooling Time of a Fuel Assembly 5 years before the Rods are Consolidated -
Water Height Above Fuel 23 feet Minimum Water Height Above Rack 10 feet /1.4 feet **
(Accident)*
Maximum Bulk Water Temperature 1500F (Normal)
Maximum Water Temperature in the 2350F/2300F**
Rack Region (Accident)*
' First value is for loss of external cooling accident.
- Although it is not considered a design basis accident, the review of. this submittal has considered the consequences of a reactor cavity seal failure accident. These values represent the water height and maximum tempera-ture for such an accident.
The following spent fuel pool time / temperature profiles were generated to confirm the criteria of 504 hours0.00583 days <br />0.14 hours <br />8.333333e-4 weeks <br />1.91772e-4 months <br /> and to establish the responses of the spent fuel pool for the worst cases of single active failures that occur. within 504 hours0.00583 days <br />0.14 hours <br />8.333333e-4 weeks <br />1.91772e-4 months <br /> ~ af ter shutdown. The results show that the spent fuel pool temperature drops to less than or equal to 1400F at or before 504 hours0.00583 days <br />0.14 hours <br />8.333333e-4 weeks <br />1.91772e-4 months <br /> in the event of a single active failure.
Specifically, the accident scenarios consist of:
,1. Mechanical Failure of One Spent Fuel Cooling Pump
- (resulting in one pump and two heat exchangers remaining operable) o Time for the discharged batch to be placed 150 hours0.00174 days <br />0.0417 hours <br />2.480159e-4 weeks <br />5.7075e-5 months <br /> in spent fuel pool o Time for pool temperature to increase from 27 hours3.125e-4 days <br />0.0075 hours <br />4.464286e-5 weeks <br />1.02735e-5 months <br /> 1200F to maximum of 1450F o Time for pool temperature to decrease 72.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> from 1450F to 1400F o Total cycle time 249.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />
- a. .
- 2. Failure of One Spent Fuel Pool Cooling Heat E'xchanger (resulting in isolation of the heat exchanger with the flow from two pumps directed to the one remaining
- heat exchanger) .
o Time for the discharged batch to be 150 hours0.00174 days <br />0.0417 hours <br />2.480159e-4 weeks <br />5.7075e-5 months <br /> placed in the spent fuel pool o Time for the pool temperature to 27 hours3.125e-4 days <br />0.0075 hours <br />4.464286e-5 weeks <br />1.02735e-5 months <br /> increase from 1200F to a maximum 1570F o Time for the pool temperature to 313 hours0.00362 days <br />0.0869 hours <br />5.175265e-4 weeks <br />1.190965e-4 months <br /> decrease from 1570F to 1400F o Total cycle time 490 hours0.00567 days <br />0.136 hours <br />8.101852e-4 weeks <br />1.86445e-4 months <br /> III. Conclusion Based on the analysis provided in Sections I and II, this proposed change to the Technical Specifications does not constitute an unreviewed safety question or a significant hazards consideration per 10 CFR 50.59 and 10 CFR 50.92 since it does not:
- 1. Increase the probability of occurrence or the consequences of an accident or malfunction of equipment important to safety. previously evaluated in the safety analysis report. The only design basis accident considere'd for the spent fuel pool is the fuel handling accident, which is not impacted by the proposed technical specification change. Since no new failure mode is identified, the proposed change does not result in an initiating event. ' The probability of failure of safety systems is not applicable since no safety systems are affected by the change.
'The operability requirements of the proposed technical specification change are designed to satisfy the design basis of the Millstone Unit No. 2 spent fuel pool 504 hours0.00583 days <br />0.14 hours <br />8.333333e-4 weeks <br />1.91772e-4 months <br /> af ter shutdown. Since at present there is no Limiting Condition of Operation for the Spent Fuel Pool Cooling System, addition of any operability requirements is an improvement.
Therefore, the proposed change does not increase the probability of exceeding the design basis of the spent fuel pool.
- 2. Create the possibility of an accident or malfunction of a different type than previously analyzed in the safety analysis report. The proposed.
change does not impact the design basis accident.and creates no new failure modes and does not create a new -accident by modifying the plant response. Since there are no failure modes associated with the change, the proposed change does not create an unanalyzed accident.
- 3. Reduce the margin of safety as defined in the Technical Specifications.
The proposed Technical Specification change has no impact on the protective boundaries, therefore, the change does not reduce the
. margin of safety provided for the protective boundaries.
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w The Federal Register, Volume 51, No. 44, page 7751 dated March 6,1986, lists examples of proposed amendments the Commission considers not likely-to involve significant hazards considerations. In accordance with example -
(ii), a proposed amendment to an operating license will likely be found to involve no significant hazards considerations if operation of the facility in accordance with the proposed amendent involves a change that constitutes an-additional limitation, restriction, or control not presently included in the -
technical specifications.
The proposed changes to the Technical Specifications conform to example (ii) of the Federal Register, Volume 51, No. 44, page 7751 dated March 6,1986 by_ providing a Limiting Condition for Operation for the Spent Fuel Pool Cooling System where none was specified previously, restricting reactor-startup until the most recently discharged refueling offload has decayed 504 ~
hours, and mitigating the consequences of a single active failure by con-trolling the temperature in the Spent Fuel Pool. The applicability of this example, as well as the fact that this proposal is responsive to a previous NRC request, supports the conclusion that this amendment involves no significant hazards considerations.