ML20199D019
| ML20199D019 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 01/13/1999 |
| From: | Nunn D SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20199D024 | List: |
| References | |
| TAC-M95861, TAC-M95862, NUDOCS 9901190264 | |
| Download: ML20199D019 (12) | |
Text
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- i. Th 50UnitRN CAufORNIA i
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as Dwight E. Nunn 1
Vice President l
An wlSON INTLRNATIONAL* Company a
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January 13, 1999 l'
U. S. Nuclear Regulatory Commission Attention:
Document Control Desk Washington, D.C.
20555 Gentlemen:
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Subject:
Docket Nos. 50-361 and 50-362 Supplement 1 to Amendment Application Nos.157 and 141, Change to 1
Technical Specification 3.9.4 " Shutdown Cooling (SDC) and Coolant Circulation -- High Water Level" and Technical i
Specification 3.9.5, " Shutdown Cooling (SDC) and Coolant 3
Circulation -- Low Water Level" l
]i San Onofre Nuclear Generating Station Units 2 and 3 1
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References:
See Enclosure 1 i
This letter provides, in Enclosure 2, the additional information as requested by the U.S. NRC in the September 8, 1998, letter (Reference 1).
This letter also provides, in Enclosure 3, Supplement 1 to Amendment Application Numbers 157 and 141 to Facility Operating Licenses NPF-10 and NPF-15, respectively, for the San Onofre Nuclear Generating Station Units 2 and 3.
These amendment applications consist of Proposed Change Number 458 (PCN-458),
Supplement 1, which replaces the original PCN-458 in its entirety.
PCN 458, Supplement 1 is a request to revise Technical Specifications (TSs) 3.9.4 and TS 3.9.5.
Revisions to the Bases B 3.9.4 and B 3.9.5 are provided for information.
Amendment Application Numbers 157 and 141 were originally submitted by Reference 2.
1 Supplement 1 is a request to conservatively restrict the required action
. completion time to close all containment penetrations providing direct access from containment atmosphere to outside atmosphere from "4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />" to "4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> or within the calculated time to boil, whichever is less." This change is to revise the Technical Specification to reflect the current practice at San Onofre Units 2 and 3.
This Supplement also updates the Significant Hazards Consideration section.
The purpose of TS 3.9.4 and TS 3.9.5 is to ensure that:
- 1) sufficient cooling is available to remove decay heat from the Reactor Coolant System, 2) water in the reactor vessel is maintained below 140*F, and 3) sufficient coolant circulation is maintained in the reactor core to minimize boron stratification leading to a boron dilution incident.
9901190264 990113
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PDR ADOCK 05000361 I
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P. O. Ikix 128 San Clemente. CA 42674 0128 949 368-1480 Fax 949-368-1490
Document Control Desk While not affecting the purpose of the TSs, PCN 458, Supplement I requests changes which will facilitate testing of Low Pressure Safety Injection System components and will permit additional flexibility in scheduling maintenance on the shutdown cooling system.
The specific requests made by PCN-458, Supplement 1 are as follows:
1)
Reduce the water level in the reactor cavity when two loops of shutdown cooling (SDC) are required from 23 feet to 20 feet above the reactor pressure vessel flange, 2)
Increase the time a required loop of the SDC system may be removed from service from up to I hour per 8-hour period to up to 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> per 8-hour period, provided the upper guide structure has been removed from the reactor pressure vessel, 3)
Allow for running only 1 loop of shutdown cooling with additional requirements when the water level in the reactor cavity is less than 20 feet but greater than 12 feet above the reactor pressure vessel flange, 4)
Add an action to be taken when operating only 1 loop of SDC with less than 20 feet of water above the reactor pressure vessel flange when the specified requirements.are not met, 5)
Make editorial changes, and 6)
Revise the completion time of the required actions 3.9.4 A.4 and 3.9.5 C.3 to include the restriction "or within the calculated time to boil, whichever is less."
Parts of this request for a TS change were made possible due to a design change which allows the SDC system to be cross-tied with the containment spray system. The NRC approved the cross-tie design change by License Amendments 106 and 95 for Units 2 and 3, respectively.
Now that this capability exists, cost savings-due to reduced outage times are possible.
By a letter dated February 15, 1995, Reference 3, the NRC issued Amendment Nos.116 and 105 to Facility Operating License Nos. NPF-10 and NPF-15 for the San Onofre Nuclear Generating Station Units 2 and 3, respectively.
These amendments were issued for the Cycle 8 refueling outages only in response to amendment applications consisting of PCN 402, Reference 4.
PCN 458 is similar to PCN 402, however, PCN 458 requests a permanent change to the technical specifications.
Although Amendment Nos. 116 and 105 were issued in time for use during the Cycle 8 refueling outages, emergent turbine generator work caused the outage plans to change.
Early in the outage it became apparent that the turbine generator work would determine the length of the outage.
Because utilizing the new technical specifications would not result in shortening the length of the Cycle 8 refueling outages, Southern California Edison (SCE) decided to maintain the more conservative limits of the original / current technical specifications.
Document Control Desk Supplement 1 to Amendment Application Nos.157 and 141 is a request to conservatively restrict the Completion Time for the Required Actions to close all containment penetrations providing direct access from containment
. atmosphere to outside atmosphere from "4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />" to "4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> or within the calculated time to boil, whichever is less." This change is to revise Technical Specifications 3.9.4 and 3.9.5 to reflect the current practice that containment closure can be achieved prior to the calculated time to boil at San Onofre Units 2 and 3.
Even though SCE was not able to take advantage of the proposed changes during the Cycle 8 refueling outages, SCE still believes the proposed changes will normally allow the required outage maintenance and testing to be scheduled and performed in a cost effective way.
These proposed TS changes will potentially i
save SCE, et al., between 14 and 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> of critical path time during future refueling outages.
The savings will exceed the minimum criteria of $100,000 over the remaining life of the plant (s) established for a Cost Deneficial Licensing Action (CBLA) submittal. Therefore, these amendment applications are considered a CBLA.
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l SCE requests approval of Amendment Application Numbers 157 and 141 to be l
effective as of the date of issuance, and-to be implemented within 30 days i
from the date of issuance.
This will provide adequate time for the necessary procedure changes and training on the new Technical Specifications.
If you need additional information on this Technical Specification change l
request, please let me know.
Sincerely, I
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j Enclosure cc:
E. W. Merschoff, Regional Administrator, NRC Region IV J. A. Sloan, NRC Senior Resident Inspector, San Onofre Units 2 & 3 l
J. W. Clifford, NRC Project Manager, San Onofre Units 2 and 3 S. Y. Hsu, Department of Health Services, Radiological Health Branch I
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References I
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References 1)
Letter from James W. Clifford (NRC) to Harold B. Ray (SCE), dated September 8,1998;
Subject:
Request for Additional Information Related to Reduced Water Level in the Refueling Cavity (TAC Nos. M95861 and l
M95862) San Onofre Nuclear Generating Station Units 2 and 3 2)
Letter dated May 8, 1996, from Dwight E. Nunn (SCE) to the Document Control Desk (NRC);
Subject:
Docket Nos. 50-361 and 50-362 Amendment Application Nos.157 and 141, Change to Technical Specification 3.9.4
" Shutdown Cooling (SDC) and Coolant Circulation -- High Water Level" and Technical Specification 3.9.5, " Shutdown Cooling (SDC) and Coolant Circulation -- Low Water Level," San Onofre Nuclear Generating Station Units 2 and 3 i
3)
Letter from Mel B. Fields (NRC) to Harold B. Ray (SCE) dated February 15, 1995;
Subject:
Issuance of Amendment for San Onofre l
Nuclear Generating Station, Unit No. 2 (TAC No. M90057) and Unit 3 (TAC No. M90058) 4)
Proposed Change Number 402, Submitted by letter from R. M. Rosenblum (SCE) to Document Control Desk (NRC) dated July 28, 1994, and l
Supplemented by letters dated January 30, and February 13, 1995;
Subject:
Request to revise Technical Specification (TS) 3.9.8.1 j
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" Shutdown Cooling and Coolant Circulation -- High Water Level," TS 3.9.8.2 " Shutdown Cooling and Coolant Circulation -- Low Water Level,"
and the Refueling Operations, Bases: 3/4.9.8"ShutdownCoolingand i
Coolant Circulation."
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i Response to the U.S. NRC Request for Additional Information i
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Page 1 of 6 NRC Requested Information 1.
On page 2 [of PCN 458, Reference 1], it is stated that time to boil curves are provided in Attachment E for 23 feet and 13 feet above the reactor vessel (RV) flange and for one foot below the RV flange.
Attachment E does not provide the minus one foot information.
Please provide this curve.
Response to Question 1:
The curves provided by Attachment E are heat up rate curves.
The paragraph on page 2 of PCN 458, Reference 1 starts out by stating we performed calculations for time to boil and then states that the heat up rates curves from the calculations were provided in Attachment E.
To clarify this confusion the following table provides both heat up rate data and time to boil data for the reactor cavity water levels of 23 feet above,13 feet above, and 1 foot below the reactor vessel flange:
Time After Shutdown (days) 5 10 30 90
-l' Below RV Flange HeatupRate*(F/hr) 209 159 100 56 Time To Boil (hr) 0.44 0.58 0.92 1.66 i
13' Above RV Flange Heatup Rate * (F/hr) 40.2 30.4 19.3 10.6 Time To Boil (hr) 2.29 3.03 4.78 8.66 23' Above RV Flange Heatup Rate * (F/hr) 24.9 18.8 11.9 6.6 Time To Boil (br) 3.70 4.89 7.72 14.0
- Heatup Rate = ATemperature / Time To Boil ATemperature = 212 F - 120 F = 92 F
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1 NRC Requested Information l
2.
It is also stated on page 2 [of PCN 458, Reference 1] that the containment can be closed within one hour for any water level above the RV flange. Please provide the time to boil for water level at the RV flange and, if this is less than one hour, please discuss how containment closure is ensured.
Response to Question 2:
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Containment closure policy and guidelines were developed in response to NUMARC 91-06, " Guidelines for Industry Actions to Assess Shutdown Management,"
(Reference 3) December 1991 and incorporated into plant shutdown procedures.
Containment closure control is in effect and maintained whenever the RCS is breached and fuel is in the containment.
Containment closure control requires containment closure prior to core boiling.
Hence, containment closure must be achievable within the calculated time to boil (TTB) at all times.
If the TTB is less than 30 minutes, then containment openings are not allowed with the exception of the Personnel Airlock / Escape Hatch, which requires a dedicated person stationed to close the Airlock Door or Escape Hatch prior to core boiling.
Additionally, Supplement 1 to PCN 458 recognizes the importance of ensuring l
containment closure prior to reaching the boiling point. Therefore, the l
current Southern California Edison (SCE) practice of assuring the containment can be closed within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> or withing the time to boil is being elevated to j
a technical specification requirement and not just a plant procedure.
At one foot below the RV flange (-l'WR), the calculated TTB at 6 days after shutdown is 28.5 minutes.
Per the containment closure guidelines, containment openings would not be allowed for this configuration. When the cavity level is raised to +12'WR, then containment openings would be permitted because the TTB is 2.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />. The demonstrated time to containment closure is less than 1 i
hour.
NRC Requested Information j
The staff believes that the phrase " containment penetration with direct 3.
access to the outside atmosphere" refers to any opening in the reactor i
building pressure boundary that provides a direct path from the atmosphere inside the reactor building to outside the reactor building.
Please confirm the staff's understanding of this phrase or, if incorrect, provide a correct description of the phrase.
i Response to Question 3 Yes, SCE agrees.
Please see the following definitior, of a Closed Containment from Attachment 1, " Definitions," of SCE operating procedure 5023-5-1.8.1, Reference 4.
The Definition step 1.5 states:
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Page 3 of 6 Closed Containment - A Containment that provides at least one integral barrier to the release of radioactive material. Sufficient separation of Containment atmosphere from the outside environment must be provided such that a barrier to the escape of radioactive material is reasonably expected to remain in place following a Reactor Core melt accident.
This can be accomplished by providing reasonable assurance that all of the following conditions are met:
1.5.1 The Equipment Hatch door is closed and held in place by at least four reasonably spaced bolts, plus additional bolts as necessary, to ensure that no gap exists in the sealing surface.
1.5.2 A minimum of one door in the Personnel Airlock and the Emergency Airlock is closed.
1.5.3 Each penetration providing access from Containment atmosphere to the outside atmosphere is closed by a valve or blind flange.
Closure by valves and blind flanges other than those used at power operation may be used if they are similar in capability to those used for Containment Isolation.
These may be constructed of standard materials and may be justified on the basis of either normal analysis methods or reasonable engineering judgement.
Plywood and plastic sheeting are not acceptable unless specifically allowed by an engineering evaluation that considers the potential effects of Containment internal pressure and combustion.
1.5.4 The Fuel Transfer Tube can be considered closed if the FTT
[ Fuel Transfer Tube] Isolation Valve, S2(3)1219MU110 is shut or the FTT is covered by a water seal of at least 6 feet (level within 1 foot of the RX [ Reactor Vessel]
Flange deck).
The Fuel Handling Building may be used as a temporary secondary containment, provided the FTT is closed or is sealed with a blind flange within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> af ter core boiling begins.
NRC Requested Information 4.
On page 7 [of PCN 458, Reference 1], it is stated that the risk of inventoryboilingandofcoredamageisstatedtobe1.5X10-5/dayand 6 x 10-9/ day, respectively, when the requested TS change is compared to the current TS requirements.
What are the current values (per day)?
What is the benefit of the anticipated outage reduction time on core damage probability during the outage and how is overall annual core damage probability affected?
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j Page 4 of 6 Response to Question 4:
o What are the current values per day?
SCE Response: Based on the current Living Probabilistic Risk Assessment (PRA) model, the current values per day for the risk of inventory boiling with two trains of shutdown cooling available with the water level at 12 feet or greater above reactor vessel flange is estimated to be 9.4E-5.
The current risk of core damage from the Living PRA model is negligible since the core uncovery time without makeup is long (i.e., about 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />) when the refueling cavity water level is 12 feet or greater above the reactor vessel flange, and an inventory makeup system is assumed to be restorable within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.
o What is the benefit of the anticipated outage reduction time on core damage probability during the outage and how is overall annual core damage probability affected?
SCE Response: The expected savings associated with PCN-458 is between 14 and 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> of outage time during future outages at each unit. The reduction of 14 to 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> in outage duration does not result in any significant impact on outage or annual core damage probability. The water level during this period is 12 feet or greater above the reactor vessel flange.
The probability of core damage during this period is negligible since the core uncovery time without makeup is about 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> and an inventory makeup system is assumed to be restorable within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.
NRC Requested Information 5.
On page 8 [of PCN 458, Reference 1], it is stated that the time to boil 6 days after shutdown [with the water level] at 23 feet is 4.0 hours0 days <br />0 hours <br />0 weeks <br />0 months <br />, and at 20 feet it is 3.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />.
These values appear to correspond to an initial temperature of 120*F in Figure 1, but the proposed revision 1s with respect to a maximum temperature of 140 F.
In the revised TS 3.9.4, Action A.4., you retain the previous 4.0 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> as completion time for containment closure as opposed to a change such as "4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> or within the calculated time to boil, whichever is less."
In the revised l
TS 3.9.5, Action C.3., you also retain the 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> in contrast to a time to boil of 2.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> as stated on page 10 of your submittal.
Please clarify the apparent inconsistencies, provide corrections if consistencies exist, and either justify retaining the 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> or submit a revision consistent with your calculations.
Note this comment applies to multiple locations in the submittal.
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'O Page 5 of 6 Response to Question 5:
The TTBs specified are referenced to an initial RCS temperature of 120 F.
The maximum RCS temperature of 140 F in the Note under LC0 3.9.4 is applicable only with the SDC loop removed from operation and includes the heatup for the 2-hour period that the SDC loop is removed from operation. When RCS temperature is above 120 F, the time-to-boil calculations performed during the refueling outage will always be based on actual RCS/SDC temperature conditions.
The containment closure time in TS 3.9.4 Action A.4 and TS 3.9.5 Action C.3 will be changed from "4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />" to "4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> or within the calculated time to i
boil, whichever is less" to be consistent with the more restrictive administrative requirements in plant shutdown procedures.
This change is being requested in Supplement 1 to to License Amendment l
Application Numbers 157 and 141 to Facility Operating Licenses NPF-10 and NPF-15, respectively, for San Onofre Nuclear Generating Station Units 2 and 3.
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This Supplement is provided in Enclosure 3.
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NRC Requested Information
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6.
Provide the basis for the maximum heatup rate of 2.6 F/hr stated on page 9.
If this value is incorrect, please provide the correct value and its basis.
Response to Question 6:
The basis for the heatup rate of 2.6 F/hr estimated at the time of the request for the San Onofre Unit 2 waiver of compliance on October 10, 1991 (Reference 5) was for the conditions present on that date, which included a cavity level of 19' WR and low decay heat associated with a refueled core at 55 days after shutdown.
The value of 2.6 F/hr was estimated prior to the conservative calculation of TTB for refueling cavity water levels performed to support a response to NUMARC 91-06 in 1993.
The heatup rate for the October 10, 1991 conditionusingthe1993calculationresultswouldbe5.1F/hr.
The 1993 calculation of TTB for cavity levels, the basis for all current heatup analyses, conservatively credits only one-half the water in the upper refueling cavity, which explains the factor of two difference.
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References 1)
Letter dated May 8, 1996, from Dwight E. Nunn (SCE) to the Document r
l Control Desk (NRC);
Subject:
Docket Nos. 50-361 and 50-362 Amendment Application Nos.157 and 141, Change to Technical Specification 3.9.4
" Shutdown Cooling (SDC) and Coolant Circulation -- High Water Level" l
and Technical Specification 3.9.5, " Shutdown Cooling (SDC) and Coolant Circulation -- Low Water Level," San Onofre Nuclear Generating Station l
Units 2 and 3 l
2)
Southern California Edison Calculation N-0220-029, " Reactor Coolant System (RCS) following Loss of Safety Display Console (SDC)"
3)
NUMARC 91-06, " Guidelines for Industry Actions to Assess Shutdown Management," December 1991 4)
Southern California Edison Station Procedure 5023-5-1.8.1 " Shutdown Nuclear Safety" 5)
Letter from R.P. Zimmerman (NRC) to R.W. Krieger (SCE) dated October 10, 1991;
Subject:
" Region V Waiver of Compliance with San Onofre Unit 2 Technical Specifications (TS) 3.9.8.1 and 3.9.8.2" l
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