ML060180262

Supplemental Response to Requests for Additional Information Regarding Topics Described by Letters Dated August 24, 2005 and October 28, 2005

ML060180262
Person / Time
Site:	Ginna
Issue date:	01/11/2006
From:	Korsnick M Constellation Energy Group, Ginna
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
1001471, TAC MC7382
Download: ML060180262 (52)

Text

Maria Korsnick R.E. Ginna Nuclear Power Plant, LLC Site Vice President 1503 Lake Road Ontario, New York 14519-9364 585.771.3494 585.771.3943 Fax maria.korsnick@constellation.com Constellation Energy I Generation Group January 11, 2006 U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 ATTENTION: Document Control Desk

SUBJECT:

R.E. Ginna Nuclear Power Plant Docket No. 50-244 Supplemental Response to Requests for Additional Information Regarding Topics Described by Letters Dated August 24, 2005 and October 28, 2005 By letter dated December 9, 2005, R.E. Ginna Nuclear Power Plant, LLC (Ginna LLC) submitted a response to an October 28, 2005 request for additional information (RAI), (TAC NO. MC7382).

In our letter we indicated that the responses denoted as "Post-LOCA Long-Term Cooling" RAls

1. 2, #3, and #5 would be submitted by January 16, 2006; the responses to that request are enclosed. Additionally, by letter dated August 24, 2005 (TAC NO. MC 7382) the NRC requested additional information regarding loss of coolant (LOCA) analysis. The response to that request is also enclosed.

Attachment 1 contains the list of regulatory commitments; specifically the response includes one new regulatory commitment:

Prior to startup from the fall 2006 refueling outage, revise the Emergency Operating Procedures (EOPs), and the attendant basis background documents, to account for the maximum times available to complete operator actions to establish simultaneous reactor coolant system injection paths. As described in regulatory commitments made in our July 7, 2005 license amendment request for extended power uprate (EPU), the commitment to modify the procedures includes the commitment to provide operations staff training on these changes.

Attachment 2 contains the Ginna LLC supplemental response to the above referenced October 28, 2005 RAI.

Attachment 3 contains the Ginna LLC response to an August 24, 2005 RAI.

With this response Ginna LLC has provided responses to all remaining written requests for additional information related to the Ginna EPU.

1001u47/

If you have any questions, please contact George Wrobel at (585) 771-3535 or george.wrobel @constellation.com.

STATE OF NEW YORK  :

TO WIT:

COUNTY OF WAYNE I, Mary G. Korsnick, being duly sworn, state that I am Vice President - R.E. Ginna Nuclear Power Plant, LLC (Ginna LLC), and that I am duly authorized to execute and file this response on behalf of Ginna LLC. To the best of my knowledge and belief, the statements contained in this document are true and correct. To the extent that these statements are not based on my personal knowledge, they are based upon information provided by other Ginna LLC employees and/or consultants. Such information has been reviewed in accordance with company practice and I believe it to be reliable.

(I Subscribed and sworn before me, a Notary Public in and for the State of New York and County of M'0n7 R ,this il dayof JanLL arII ,2006.

WITNESS my Hand and Notarial Seal:

Notary Public' SHARON L MILLER No try PWtk, Sha eof New York My Commission Expires: /l4 2 I- 0 G Reqai No. 01M16017755 monm. EON 21,20

Attachments Cc: S. J. Collins, NRC P. D. Milano, NRC Resident Inspector, NRC Mr. Peter R. Smith New York State Energy, Research, and Development Authority 17 Columbia Circle Albany, NY 12203-6399 Mr. Paul Eddy NYS Department of Public Service 3 Empire State Plaza, 10th Floor Albany, NY 12223-1350

ATTACHMENT 1 R.E.Ginna Nuclear Power Plant List of Regulatory Commitments The following table identifies those actions committed to by R.E. Ginna Nuclear Power Plant, LLC in this document. Any other statements in this submittal are provided for information purposes and are not considered to be regulatory commitments.

Regulatory Commitment Due Date Modify Emergency Operating Procedures (EOPs) Prior to Start up from 2006 RFO and Bases to ensure operator actions account for the maximum times available to establish simultaneous RCS injection paths I 1

ATTACHMENT 2 RESPONSES TO NRC RAls 2,3,5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28, 2005 Post LOCA LTC RAI #2

2. Small breaks were not addressed. The boric acid concentration for the limiting SBLOCA needs to be evaluated. Provide a summary of the results to show that the boric acid concentration is not sufficient to cause precipitation should the operators inadvertently depressurize the reactor coolant system (RCS) in a rapid manner.

Response

Breaks smaller than 4 inches require operator action to initiate cooldown and depressurization. A review of Emergency Procedures and simulator experience indicates that operators will begin RCS depressurization within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> of the pipe break. If RCS depressurization to upper plenum injection (UPI) cut-in pressure occurs within the calculated system depressurization time", flushing flow will be available and boric acid precipitation cannot occur. Using the results from a NOTRUMP Small Break LOCA Boric Acid Analysis, a *system depressurization time" was calculated using assumptions consistent with the longest RCS depressurization and the boric acid solution solubility limit corresponding to atmospheric conditions (29.27 wt0 /o). For very small breaks (less than 1.1 inches) boric acid precipitation is not a concern because natural circulation will not be lost, or it will be restored within the system depressurization time. A comprehensive description of the boric acid precipitation phenomena and coping strategy for the full spectrum of break sizes, as well as a description of the NOTRUMP Small Break Post-LOCA Cooldown Analysis is provided in Attachment A.

Inadvertent RCS depressurization will not cause boric acid precipitation when it occurs before the "system depressurization time" since the boric acid atmospheric solubility limit will not be exceeded at any time. Operator coping strategies are such that, after the "system depressurization time" the UPI flow or natural circulation flow will be sufficient to flush the core with or without a full system depressurization.

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ATTACHMENT 2 RESPONSES TO NRC RAIs 2,3,5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28, 2005 Post LOCA LTC RAI #3

3. Provide information to show that for the largest break that does not actuate upper plenum injection (UPI) (where a cooldown is required) that there is sufficient time to perform this function given an appropriate precipitation time based on consideration of the four items in item 1 above.

Response

A Ginna EPU NOTRUMP Small Break Post-LOCA Cooldown Analysis showed that a 4 inch break or greater will depressurize the RCS to the UPI cut-in pressure without operator actions prior to reaching the boric acid atmospheric solubility limit (see discussion in Attachment A). For smaller breaks down to approximately 1.1 inches, the operators will depressurize the RCS in accordance with Emergency Procedure ES-1.2, Post LOCA Cooldown and Depressurization. The Small Break LOCA Boric Acid Analysis and the small break cooldown analyses described in Attachment A demonstrate that the plant will be depressurized and dilution flow will flush the core prior to the atmospheric solubility limit being reached.

For breaks smaller than 1.1 inches, analyses were performed to demonstrate that boric acid precipitation is not a concern because natural circulation will not be lost, or it will be restored within the system depressurization time calculated for the small break LOCA scenario. A comprehensive description of the boric acid strategy for the full spectrum of break sizes is provided in Attachment A.

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ATTACHMENT 2 RESPONSES TO NRC RAIs 2,3,5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28,2005 Post LOCA LTC RAI #5

5. Once UPI initiates, at what time following an LBLOCA would the core steaming rate be insufficient to entrain the hot-side injection?

Response

UPI flow provides the core flushing flow for cold leg breaks. For a large break where the RCS depressurizes rapidly, the UPI will provide a flushing flow even though there is no significant buildup of boric acid in the core. For small breaks, where the RCS depressurization is delayed and core region boric acid can accumulate, the UPI will provide a flushing flow that will dilute the core. In either case, entrainment around the loops would reduce the volume of flushing flow that provides core dilution. The limiting condition for entrainment that would reduce the volume of flushing flow would be a condition where the top of mixture level is into the hot legs and steam flow through the loops carries liquid around the loop. A liquid entrainment threshold for this scenario is calculated below. Note that entrainment around the loops is not relevant to large break LOCA core cooling since the large break LOCA ECCS evaluation model demonstrates the capability to cool the core with UPI flow.

The liquid entrainment threshold in the hot leg can be established from applying the Ishii-Grolmes (Reference 1) or Wallis-Steen (Reference 2) liquid entrainment onset criteria as shown below. These entrainment correlations are valid for flow conditions where the liquid phase does not take up a significant volume of the pipe (such as in the hot legs in post-LOCA) and viscous effects in the liquid are not dominant, that is, that the liquid phase is in the turbulent regime. Note that the correlations have very similar form; however, the Ishii-Grolmes entrainment onset criterion uses liquid phase viscosity whereas Wallis-Steen uses gas phase viscosity.

Ishil-Grolmes Liquid Entrainment Onset Criterion The liquid entrainment onset correlation per Reference 1 can be expressed as follows:

jg 2 No 8(P.') i) for N, < I where NP is the viscosity number and jg is the superficial velocity of gas phase.

Wallis-Steen Liquid Entrainment Onset Criterion The liquid entrainment onset correlation per Reference 2 can be expressed as follows:

ig 2 'T2 (P' t i where 7Z2 represents dimensionless gas velocity. Steen suggested a value of 2.46E-04 for A 2 , however, a more conservative value of 2.OE-04 will be used for this calculation.

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ATTACHMENT 2 RESPONSES TO NRC RAls 2,3,5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28,2005 The following properties of saturated liquid and gas phases of water at atmospheric conditions (14.7 psia) are used in the above correlations:

1f = surface tension of liquid = 4.03E-03 Ibf/ft

= viscosity of liquid = 5.93E-06 Ibf-s/ft2

-af ju = viscosity of gas = 2.56E-07 Ibf-s/ft 2 Pf = density of liquid = 59.8 Ibmf 3 Pg = density of gas = 0.0373 Ibm/ft3 Liquid Entrainment Threshold in Terms of Hot Lea Superficial Steam Velocity Using the above properties as input, the following results are obtained for the liquid entrainment threshold in terms of superficial steam velocity in the hot leg:

JgISHII-GROLUES = 86.6 fWs with N,. = 0.000756 JgWALLJS-STEEN = 126 ft/s Applying the lower value of 86.6 ft/s obtained from Ishii-Grolmes with comparable steam flow in each hot leg, the following total core steam mass flow rate at the entrainment threshold becomes:

mcoresteam = ig.ISH11-GROLMES 2* AhotIg - Pg = 29.65 Ibm/s where for a single hot leg, AhotCg = 4.59 ft2.

The decay heat fraction can be related to the core steam mass flow rate as follows, where PWL is the licensed power of 1811 MWt (including calorimetric uncertainty) is applied.

mcoreseam = [PwL PIP *948BtulsII(h +Ahs)

For Ginna with no subcooling and atmospheric conditions, a decay heat fraction is obtained.

PI Po = 0.0168 Decay Heat Fraction This decay heat fraction corresponds to approximately 4300 seconds after shutdown for Appendix K decay heat and approximately 2400 seconds for 1979 ANS+2a decay heat.

Therefore, steam flow in the hot legs should drop below the entrainment threshold at about 1 hr. 12 min. based upon the Appendix K decay heat function. Since the LOCA Boric Acid Analysis (see Attachment A) showed that hot side dilution flow (via UPI) is not needed until after 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> after the pipe break, the volume of flushing flow that provides core dilution will not be reduced due to hot leg entrainment.

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ATTACHMENT 2 RESPONSES TO NRC RAls 2,3,5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28, 2005

References:

1. Ishii, M.; Grolmes, M. A., Inception Criteria for Droplet Entrainment in Two-Phase Concurrent Film Flow, AlChE Journal, Vol. 21, No. 2, pp. 308-319, 1975.

2. Wallis, G. B., One-Dimensional Two-Phase Flow, pp. 390-393,1969.

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ATTACHMENT 2 RESPONSES TO NRC RAls 2,3,5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28, 2005 Attachment A Ginna EPU Long Term Cooling Boric Acid Precipitation Post-LOCA Strategy Background/Summary Ginna is an upper plenum injection (UPI) design, i.e., the low head safety injection pumps (RHR pumps) deliver flow directly to the upper plenum, while the high head SI pumps inject into the RCS cold legs. For this reason, the hot-leg switchover procedure that is applied to the typical three-loop and four-loop Westinghouse designs to ensure long term core cooling is not applied to Ginna. During a LOCA, safety injection signal starts both high head SI pumps and low head RHR pumps. When RCS pressure decreases below the low head RHR injection pressure (140 psia) simultaneous hot (UPI) and cold side (SI) injection will occur. Upon entering the sump recirculation phase operators are instructed to establish recirculation flow using the RHR pumps which will maintain UPI, and terminate flow from the high head SI pumps. After a period of time (less than 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />, 30 minutes), operators will be instructed to restart the high head safety injection pumps to re-establish simultaneous cold side and hot side (UPI) injection to provide long term core cooling for all LOCA scenarios.

Three categories of LOCA break sizes were considered for the boric acid precipitation evaluation: (1) large or intermediate breaks (greater than approximately 4" in diameter) where the RCS pressure rapidly decreases to the UPI initiation pressure (140 psia) with no operator action, (2) small breaks (between approximately 1.1" and 4" in diameter) where RCS pressure decreases but stabilizes above the UPI initiation pressure, and (3) very small breaks (approximately 1.1" in diameter and smaller) where high head safety injection refills the RCS and natural circulation is established.

For large or intermediate breaks in the cold leg, boric acid precipitation cannot occur since the RCS will depressurize quickly and upper plenum injection will provide flushing flow through the core.

For large or intermediate breaks in the hot leg, the core region boric acid concentration will only begin to increase with the termination of high head safety injection to the cold legs.

Calculations for a large break LOCA scenario have shown that the boric acid solution will approach the solubility limit for atmospheric pressure conditions at 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />, 49 minutes after the termination of SI to the cold leg. For the EPU, the Ginna Emergency Operating Procedure ES-1.3, Transfer to Cold Leg Recirculation will be revised to instruct operators to re-establish cold leg SI (i.e. simultaneous injection) no later than 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />, 30 minutes after the termination of SI in the cold leg. In this case boric acid precipitation will be prevented.

There are no limitations on early switchover to simultaneous injection.

For small breaks in the cold leg, RCS pressure will stabilize above the UPI initiation pressure and the core region boric acid concentration will begin to increase prior to upper plenum injection. Emergency Operating Procedure ES-1.2, Post-LOCA Cooldown and Depressurization directs the operators in this scenario to depressurize the RCS using the condenser steam dumps or SG atmospheric relief valves. Calculations for depressurization after a small break LOCA scenario have shown that the boric acid solution will not approach the solubility limit until approximately 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, 48 minutes after the break. When the RCS is depressurized through operator action to below 140 psia, UPI using the RHR (low head SI) pumps will initiate and this will provide immediate core flushing flow.

Operational experience, simulator training, and NOTRUMP small break LOCA cooldown/depressurization analyses indicate that operators will depressurize the RCS to less than 140 psia before 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, 48 minutes after the break. Results from the NOTRUMP Small Break LOCA Boric Acid Analysis demonstrate that if UPI is initiated within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, 48 minutes after the break boric acid precipitation is precluded even for sudden RCS depressurization to atmospheric pressure.

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ATTACHMENT 2 RESPONSES TO NRC RAls 2,3,5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28, 2005 For small breaks in the hot leg, RCS pressure will again stabilize above the UPI initiation pressure; however the core boric acid concentration will not increase until the high head cold leg Si is terminated. Operators are again directed to depressurize the RCS, and maintain UPI using the RHR pumps on recirculation and terminate the high head SI as necessary. Once high head Si to the cold leg is terminated, this scenario is bounded by the large hot leg break scenario where cold leg Si (i.e. simultaneous injection) will be re-established no later than 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />, 30 minutes after termination.

For very small hot leg or cold leg breaks (less than approximately 1.1" in diameter) the RCS remains pressurized such that natural circulation will not be lost, or if lost, will be re-established. Emergency Operating Procedure (EOP) actions will cooldown and depressurize the RCS under controlled conditions with eventual realignment to RHR normal shutdown cooling. Natural circulation or RHR normal shutdown cooling will dilute any buildup of boric acid in the core.

A summary of the GINNA EPU long term cooling post-LOCA boric acid control strategy for various size breaks is shown in Table 1.

To summarize the procedural requirements related to preventing boric acid precipitation:

1. During a small break LOCA when RCS depressurization to the UPI injection pressure does not occur without operator action, operators will take action to initiate a plant cooldown and depressurization at the maximum Technical Specification allowed cooldown rate within one hour after the break occurs.

2. During a small break LOCA the RCS will be depressurized to less than the UPI injection pressure within six hours and 30 minutes after the break occurs.

3. During a LOCA when SI flow to the cold leg is terminated upon entering sump recirculation, Si flow to the cold leg will be re-established within 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> and 30 minutes after initial termination.

These procedural requirements will be captured in procedure background documents and will be incorporated into the operator training program. The capability to meet these requirements will be verified prior to the startup for the EPU and periodically verified as part of operator re-qualification training thereafter.

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ATTACHMENT 2 RESPONSES TO NRC RAls 2,3,5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28, 2005 BREAK SIZE SCENARIO ANALYSIS DEG 1.0 FT2 0.8 T2 l Large or Intermediate Breaks Breaks of this size will depressurize LB Mixing Volume 0.6 FT2 to RHR cut-in pressure without Analysis and operator action. LB Boric Acid Analysis 8.0 IN 6.0 IN 4.0 IN 2.0 IN Small Breaks For breaks of this size, operators will take 1.8 IN action to depressurize RCS to RHR cut-in SB Boric Acid Analysis 1.4 IN pressure before boric acid atmospheric and Depressurization/

solubility limit is reached. Cooldown Analysis 1.4 IN 1.3 IN 1.2 IN 1.1 IN Very Small Breaks Natural circulation is lost but regained 1.0 IN before boric acid atmospheric solubility 0.9 IN limit is reached.

SB Depressurization 0.8 IN 0.7IN 0.6 IN

} Very Small Breaks Natural circulation is not lost.

Analysis Natural circulation will keep the core diluted.

0.5 IN 0.375 IN - Charging Flow Makeup Capacity

_-.1 Table IGINNA EPU -Long Term Cooling Post-LOCA Boric Acid Control Strategy 9

ATTACHMENT 2 RESPONSES TO NRC RAls 2,3,5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28,2005 Large Break LOCA Boric Acid Analysis Description A Large Break LOCA Boric Acid Analysis was performed to address the limiting large break LOCA scenario, that is, breaks in the hot leg where the core region boric acid concentration will begin to increase with the termination of high head safety injection to the cold legs.

The Large Break LOCA Boric Acid Analysis was based on calculations that used a time-varied mixing volume extracted from modified Ginna WCOBRA/TRAC Large Break LOCA Evaluation Model computer runs. The modifications to the Ginna WCOBRAITRAC Large Break LOCA Evaluation Model were as follows:

• Appendix K decay heat was used (1971 ANS, Infinite Operation + 20%).

• A hot leg break was modeled (the limiting large break scenario for boric acid buildup).

• SI flows were adjusted to better represent long-term SI delivery including sump recirculation.

• Hot rod and hot assembly power was adjusted to allow code execution. However, total core power was preserved.

• The transient was extended to beyond switchover to sump recirculation.

The use of the WCOBRAITRAC Large Break LOCA Evaluation Model in this analysis has the following advantages.

a) Appropriate capturing of system effects on core mixture level and core void fractions.

b) Appropriate capturing of UPI effects on core mixture level and core void fractions.

c) Direct source for mixing volume and core boiloff rates for the early part of the transient.

d) All other input assumptions were consistent to those used in 10 CFR 50.46 PCT calculations.

Items a) and b) above satisfy the NRC request to consider void fractions and system effects in the calculation of core mixing volume (Post-LOCA LTC RAI#1 [a,b]). The significant assumptions in the large break boric acid precipitation calculations are as follows:

1. The core region mixing volume is limited to the region from the bottom of the active fuel to the bottom elevation of the hot legs plus 50% of the lower plenum (justified in Reference 1) volume (the region from the bottom of the active fuel to the bottom of the reactor vessel). Hot leg volume or barrel/baffle/former region volumes are not included.

2. Core boiloff rates are obtained in part from the Ginna WCOBRA/TRAC Large Break LOCA Evaluation Model computer runs. The core boiloff rate used in the calculations is given in Figure 3.

3. Time-based liquid mixing volume is extracted from the Ginna WCOBRAITRAC Large Break LOCA Evaluation Model computer runs. The core and upper plenum average voiding assumed in the analysis is given in Figure 1. The associated mixing volume used in the calculations is given in Figure 2.

4. The calculations were based on a vessel pressure of 14.7 psia.

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ATTACHMENT 2 RESPONSES TO NRC RAls 2,3, 5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28, 2005

5. An atmospheric boric acid solution solubility limit of 29.27 wt% is assumed. This represents the solubility limit at the atmospheric boiling point of a boric acid and water solution (Reference 2). No credit was taken for containment overpressure.

No credit was taken for the increased boric acid solution solubility limit due to the presence of containment sump PH additives.

6. Appendix K decay Heat (1971 ANS, Infinite Operation + 20%) was used in all calculations.

Item 5 above satisfies the NRC request to justify the boric acid precipitation limit (Post-LOCA LTC RAI#1[c]) Item 6 above satisfies the NRC request to use 10 CFR 50 Appendix K decay heat (Post-LOCA LTC RAI#1 [d]).

Results The results of the large break boric acid precipitation calculations are shown in Figure 3.

As seen in Figure 3, for large hot leg breaks with no cold leg safety injection during an extended period in sump recirculation, boric acid precipitation will be prevented if cold leg safety injection (i.e. simultaneous injection) is re-established 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />, 49 minutes after the termination of safety injection in the cold leg. This is based on a calculated minimum time to terminate Si to the cold leg of 24 minutes after the break. Figure 3 also shows core boil-off, Si dilution flow, and the rate of dilution of core region if dilution flow is initiated at 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />, 30 minutes after the earliest expected termination of cold leg safety injection.

Small Break LOCA Boric Acid Analysis Description A Small Break LOCA Boric Acid Analysis was performed to address the limiting small break LOCA scenario, that is breaks in the cold leg where the RCS pressure will stabilize above the UPI initiation pressure and the core region boric acid concentration will begin to increase prior to upper plenum injection. This analysis provides the time available to depressurize the RCS to below 140 psia through operator action prior to reaching the boric acid solution solubility limit. Once the RCS is below 140 psia, the UPI will initiate and will provide immediate core flushing flow. The boric acid solution solubility limit is based on atmospheric conditions to account for an inadvertent, sudden RCS depressurization.

The Small Break LOCA Boric Acid Analysis was based on calculations that used a time-varied mixing volume and core boil-off extracted from extended Ginna NOTRUMP Small Break LOCA Evaluation Model computer runs. A 4 inch break was selected since the Ginna EPU NOTRUMP Small Break Post-LOCA Cooldown Analysis (discussed in the next section) showed that a 4 inch break or greater will depressurize the RCS to RHR cut-in pressure without operator actions prior to reaching the boric acid atmospheric solubility limit. The RCS pressure versus time for a 4 inch break is given in Figure 4. The modeling features of these runs were as follows:

• Appendix K decay Heat (1971 ANS, Infinite Operation + 20%).

• Cold Leg Break (the limiting small break scenario for boric acid buildup).

• Sump recirculation flows were modeled.

• Transients were run beyond switchover to sump recirculation.

The use of the Ginna NOTRUMP Small Break LOCA Evaluation Model in this analysis has the following advantages.

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ATTACHMENT 2 RESPONSES TO NRC RAls 2,3,5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28, 2005 a) Capturing of system effects on core mixture level and core void fractions (credited only to bottom of hot leg).

b) Provided direct source for mixing volume and core boiloff rates.

c) Consistency with assumptions used in 10 CFR 50.46 PCT calculations.

Item a) above satisfies the NRC request to consider void fractions and system effects in the calculation of core mixing volume (Post-LOCA LTC RAI#1[a,b]). The significant assumptions in the small break boric acid precipitation calculations are as follows:

1. Time-based liquid mixing volume and core boiloff rates are extracted from the Ginna NOTRUMP Small Break LOCA Evaluation Model computer runs. The core and upper plenum average voiding assumed in the analysis is given in Figure 5.

The associated mixing volume used in the calculations is given in Figure 6.

2. Core region boric acid concentrations are calculated assuming a 120 psia RCS pressure.

3. The core region mixing volume is limited to the region from the bottom of the active fuel to the bottom elevation of the hot legs plus 50% of the lower plenum (justified in Reference 1) volume (the region from the bottom of the active fuel to the bottom of the reactor vessel). Hot leg volume or barrel/baffle/former region volumes are not included.

4. An atmospheric boric acid solution solubility limit of 29.27 wt% is assumed. This represents solubility limit at the atmospheric boiling point of a boric acid and water solution (Reference 2). No credit was taken for containment overpressure. No credit was taken for the increased boric acid solution solubility limit due to the presence of containment sump pH additives.

5. Appendix K decay Heat (1971 ANS, Infinite Operation + 20%) was used in all calculations.

Item 4 above satisfies the NRC request to justify the boric acid precipitation limit (Post-LOCA LTC RAI#1[c]) Item 5 above satisfies the NRC request to use 10 CFR 50 Appendix K decay heat (Post-LOCA LTC RAI#1 [d]).

Results The results of the small break boric acid precipitation calculations are shown in Figure 7.

As seen in Figure 7, for small breaks where delayed RCS depressurization would occur, the boric acid solution will not approach the solubility limit until approximately 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, 48 minutes after the break. If the RCS is depressurized through operator action to below 140 psia, UPI using the RHR (low head SI) pumps will initiate and this will provide immediate core flushing flow. Cooldown/depressurization calculations show that operators could depressurize the RCS to less than 140 psia long before 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, 48 minutes. Figure 7 also shows core boil-off, Si dilution flow, and the rate of dilution of core region once dilution flow is initiated.

Small Break Post-LOCA Cooldown Analysis A range of break sizes from 0.75-inch to 1.5-inches were studied to identify the smallest cold leg break size for Ginna that would result in the loss of natural circulation and therefore 12

ATTACHMENT 2 RESPONSES TO NRC RAls 2,3,5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28,2005 result in a situation that could potentially lead to inadvertent boric acid precipitation. The important modeling features are as follows:

1. Appendix K analysis assumptions consistent with those used for design basis Small Break LOCA analysis.

2. Operator action to start plant cooldown per emergency operating procedure ES-1.2 commences at 3,600 seconds (1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />) into the transient using 1 atmospheric dump valve (ADV) per steam generator. The cooldown rate is limited to a maximum of 1002F/hr.

Based on the results of these studies, it was determined that breaks approximately 0.8-inch equivalent diameter and less will not lose natural circulation, whereas larger ones will. It is quite possible that during the cooldown process these larger breaks could potentially regain natural circulation at some point; however, there will be some break size where this does not occur. For Ginna, this occurs for approximately a 1.1-inch equivalent diameter break.

Figures 8 and 9 show the broken loop hot leg and cold leg liquid flow for the 0.8-inch and 1.1-inch breaks, respectively. The pressurizer pressure and broken loop hot leg mixture temperature for these same breaks are shown in Figures 10 and 11 and the inner vessel mixture level is shown in Figures 12 and 13.

The 1.1-inch break demonstrates the cooldown aspects for breaks where natural circulation is lost and not regained. This break size establishes the maximum time required to cooldown and depressurize the RCS to the UPI cut-in pressure. This analysis shows that the operators will be capable of depressurizing the RCS to the UPI cut-in pressure within approximately 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />, 15 minutes after the break occurs assuming the cooldown begins within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> after the break occurs.

Attachment A References

1. Westinghouse Letter LTR-LIS-05-56, Revision 0, 'Waterford 3 Uprate RAls, Transmittal of Summary of MHI BACCHUS Tests," dated 02-03-05.MHI Tests.

2. P. Cohen, P., 1969, Water Coolant Technology of Power Reactors, Chapter 6, "Chemical Shim Control and pH Effect," ANS-USEC Monograph.

13

ATTACHMENT 2 RESPONSES TO NRC RAls 2,3,5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28, 2005

.8

.75

.7 0

U- .65

.6

.55

.5 Time (s)

Figure 1 Large Break LOCA Boric Acid Concentration Analysis - Core/Upper Plenum Average Vold Fraction versus Time 14

ATTACHMENT 2 RESPONSES TO NRC RAIs 2,3,5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28,2005 480 460-440-380 0 10000 200D0 300D0 4000 Time (S)

Figure 2 Large Break LOCA Boric Acid Concentration Analysis - Mixing Volume versus Time 15

ATTACHMENT 2 RESPONSES TO NRC RAls 2, 3, 5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28, 2005 GINNA EPU LARGE BREAK LOCA - 14.7 PSIA J3oric Ac d Concentrat ion (frncticn)

- CRIC ACID WITH CL 'i TERl'INA- :N AT 24 WIN

---

CILU- ON WH RESlOREO CL SI hcss Fiow Rnole ( I bmn/s s

____--_CORE DCILOF-

--- Ct Si FLOW AT b.5 NRS A: rER -ERYINATION

.5 100

.4 80 C,

60 I--E 0

.3 -o E

L.)

I--, a, 0

Q-0

-o C,

.2 40 .

0 En 0

0 m

.1 20 0 0 Figure 3 Large Break LOCA Boric Acid Concentration Analysis - Vessel Boric Acid Concentration I Boiloff and Dilution Flow versus Time 16

ATTACHMENT 2 RESPONSES TO NRC RAIs 2,3,5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28, 2005 RGE 4.0 Inch Transient RCS Conditions / Pressurizer Pressure PFN 9 0 0 PRESSURIZER

- --- ' LHSI Cut-in Pressure 0-a-_

ECa, a,

tW CL 0 5000 10000 15000 20000 25000 Time (s)

Figure 4 Small Break LOCA inch Break RCS Depressurization Without Operator Actions 17

ATTACHMENT 2 RESPONSES TO NRC RAIs 2,3,5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28,2005

.33

.32

.31

.3 C:

0 C-0 L.. .29 U-

-o ---

.28

.27

.26 I I I I I I I I I

.25 I I U 10000 20000 30000 40000 Time (s)

Figure 5 Small Break LOCA Boric Acid Concentration Analysis - CoretUpper Plenum Average Vold Fraction versus Time 18

ATTACHMENT 2 RESPONSES TO NRC RAIs 2,3,5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28, 2005 610 605 -

600

~2595 CD 19)020030000 40000 Figure 6 Small Break LOCA Boric Acid Concentration Analysis - Mixing Volume versus Time 19

ATTACHMENT 2 RESPONSES TO NRC RAIs 2, 3. 5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28, 2005 GINNA EPU SMALL BREAK LOCA - 120 PSIk Boric Acid Concentroticn (fro.Lion)

NC UPI DILUTION FLOW

- - - - uPI DILUTION FLOW AT 6.5 HRS UI Moss F ow Rcle (Ibm/sJ CORE BOILOFF

_-- UP FrLOYW

.4 100 80

.3 0

UZ-U, E

I._ 60 6-1 D0 0

0) a>

.2 M Q

CD 0 02 C-, 40 Lo 0

LU 0_

20 0 0 Figure 7 Small Break LOCA Boric Acid Concentration Analysis - Vessel Boric Acid Concentration I Bolloff and Dilution Flow versus Time 20

ATTACHMENT 2 RESPONSES TO NRC RAIs 2,3,5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28, 2005 Broken Loop Hot Leg Liquid Flow

--- - Broken Loop Cold Leg Liquid Flow 1000 900 800 c/,

E

-o 700 aO U,

COr 600 3',

0 en mo 500 400 300 Figure 8 0.8-Inch Break Broken Loop Hot Leg and Cold Leg Liquid Flow 21

ATTACHMENT 2 COOLING RESPONSES TO NRC RAIs 2,3,5 REGARDING POST-LOCA LONG-TERM OCTOBER 28, 2005 Broken Loop Hot Leg Liquid Flow

- -- - Broken Loop Cold Leg Liquid Flow 1000 I-I I I II I I II II I I I~ I II 800 I I Ii I III II I II II II.

I

____ _I~

I Ii Ii1 I- I W

E I I I III I I I I II a0 600 I__

IiI 1-I V II II I'II 'I II III 11 Ii-0- _1.

II

-a 0

E- 400 0

uM I

200 I

I Ii 50 II I00i~o 0

0 5000t 10000 15000 20000 Time (s)

Figure 9 1.1-Inch Break Broken Loop Hot Leg and Cold Leg Liquid Flow 22

ATTACHMENT 2 RESPONSES TO NRC RAls 2,3,5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28, 2005 Pressure (psia)

Pressurizer Pressure

- --- LHSI Cut-In Pressure (140 psia)

Temperature (F)

---

Broken Loop Hot Leg Mixture Temperature 2500 650 K

2000 600

. ij~-I \ - ,_

U-(1,1500 - II - 4 4. "'

---

I 550 I

a, 0 0-1000 500 E L@a 0L __-N __ Q) 0-500 j "vsss~s> 450

- - - -- - .-.. - - - -1 - - - - - - - -

I_ _ _ __ __

I_____ __ __ ._ __I I I SM 0 2000 4000 6000 8000 100 00 Time (s)

Figure 10 0.8-Inch Break Pressurizer Pressure and Broken Loop Hot Leg Mixture Temperature 23

ATTACHMENT 2 RESPONSES TO NRC RAls 2,3,5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28,2005 Pressure (psia)

Pressurizer Pressure

- -- - LHSI Cut-In Pressure (140 psia)

Temperature (F)

---

Broken Loop Hot Leg Mixture Temperature 2500 650 600 2000 ' - - - L 550

,, 1500 500 a 0)

L._ 0 en 450 0-a) 1000 E 400 500 350 0 300 0o 5000 15000 2000 D0 Time (s)

Figure 11 1.1-Inch Break Pressurizer Pressure and Broken Loop Hot Leg Mixture Temperature 24

ATTACHMENT 2 RESPONSES TO NRC RAls 2,3,5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28,2005 Inner Vessel Mixture Level

- - - - Top of Hot Leg Elevation

---

Top of Core Elevation 32 30 28 lI, I I 0 26

=3 24 22 20 0 2000 4000 6000 8000 10000 Time (s)

Figure 12 0.8-Inch Break Inner Vessel Mixture Level 25

ATTACHMENT 2 RESPONSES TO NRC RAIs 2,3,5 REGARDING POST-LOCA LONG-TERM COOLING OCTOBER 28,2005 Inner Vessel Mixture Level

-- -- Top of Hot Leg Elevation

---

Top of Core Elevation 32 30 28 4-24 I

22 20 10000 Time (s)

Figure 13 1.1-Inch Break Inner Vessel Mixture Level 26

ATTACHMENT 3 RESPONSES TO NRC RAls REGARDING LOCA ANALYSES AUGUST 24,2005 LOCA RAI #1 Regarding the small-break LOCA analysis, the licensee evaluated only the 1.5, 2, and 3-inch diameter line breaks, with only limited plots provided for the 2-inch break, in its application. In its August 15, 2005, supplemental letter, the licensee stated that no core uncovery occurred for 4-inch and 6-inch break sizes. However, the licensee did not provide documentation to support its statement. Further, the integer break spectrum approach is too coarse to identify the worse case peak clad temperature (PCT). Also, the analysis of a severed cold-leg injection line was not provided.

Provide: (1) an analysis of break sizes up to and including 1.0 ft 2 in area, including break sizes other than integer break sizes to demonstrate that the worst break has been identified, (2) the major response parameters for the break spectrum, and (3) the NOTRUMP nodalization diagram.

Response

See RAI response to November 3, 2005 letter LOCA Analysis RAI #2, RAI response to October 28, 2005 letter SBLOCA RAI #4 and SBLOCA RAI #5. The NOTRUMP nodalization diagram utilized for the Ginna SBLOCA analysis is the standard Westinghouse NOTRUMP noding diagram and is identical to that provided to the NRC via Reference 1, Enclosure 2, page 125 of 314.

References (1) FirstEnergy Nuclear Operating Company (FENOC) Letter L-05-112, "Beaver Valley Power Station, Unit Nos. 1 and 2, BV-1 Docket No. 50-334, License No. DPR-66, BV-2 Docket No.

50-412, License No. NPF-73, Responses to a Request for Additional Information in Support of License Amendment Request Nos. 302 and 173, July 8, 2005.

LOCA RAI #2 There were no quantitative analysis results supplied justifying the operator action time to reinitiate cold-side injection to control boric acid precipitation following a LOCA. No boron concentration vs. time curves were provided for the limiting breaks. No analyses of breaks where the reactor coolant system pressure remains above the residual heat removal pump shut off head were provided nor was the effect of the timing for reinitiating cold-side injection identified to show sufficient time exists to control boric acid concentration for small breaks. The margin in flushing flow was not identified nor was the time needed to turn around the boric acid concentration once flushing begins. The detail of how the boron concentration was calculated was also not provided.

Provide the following information concerning the boron concentration calculation:

a. Does the mixing volume vary with time?

b. Was the loop resistance taken into account in calculating the mixing volume?

c. What constitutes the mixing volume?

The minimum injection temperature and maximum boron concentration in the core was not identified to demonstrate that precipitation is precluded at the time to activate cold-side injection.

The 1975 methods cited in the submittal for calculating boric acid concentration contain many unsubstantiated assumptions. See the Westinghouse-CE Topical Report CENPD-254 as an example of the analysis methods and results needed in order to complete the review of long-term cooling performance.

27

ATTACHMENT 3 RESPONSES TO NRC RAls REGARDING LOCA ANALYSES AUGUST 24,2005

Response

See Attachment 2 to this letter and RAI responses to October 28, 2005 letter Post-LOCA LTC RAls #1-5, Post-LOCA LTC RAls, #8, Post-LOCA LTC RAls, #10, and Post-LOCA LTC RAls,

1. 14.

LOCA RAI #3 Additional analysis results are also required for the best-estimate large-break LOCA analysis.

Only the PCT plot for the hot rod and hot bundle were provided for the limiting break.

Provide the complete analysis results including all of the key major response parameters. Also, did the analysis include downcomer boiling effects and what was the worst single failure if downcomer boiling occurs? What containment pressure was assumed?

Response

Additional plots for the limiting LBLOCA PCT case are provided on the following pages to illustrate the key major response parameters for this transient.

Figure 1.1 is a plot of the pressurizer pressure throughout the transient. Figure 1.2 is a plot of the mass flow rate through the split break, and Figure 1.3 of the void fraction in both the intact and broken loop pumps. Figure 1.4 is a plot of the vapor flow rate at the top of the core for the first 20 transient seconds, and Figure 1.5 a plot of the total flow rate at the bottom of the core for the same time period.

Figure 1.6 is a plot of the accumulator injection flow, Figure 1.7 a plot of the High Head Safety Injection Flow into the intact cold leg, and Figure 1.8 a plot of the Low Head Safety Injection Flow into the upper plenum. Figures 1.9, 1.10, and 1.11 are plots of the lower plenum, downcomer, and core collapsed liquid levels, respectively. The reference point for the lower plenum liquid level is the bottom of the vessel. The reference point for the downcomer liquid level is the point at which the outside of the core barrel, if extended downward, intersects with the vessel wall. The reference point for the core collapsed liquid levels is the bottom of the active fuel.

The vessel fluid inventory throughout the transient is plotted in Figure 1.12. Figure 1.13 is a plot of the Peak Clad Temperature for all 5 rods modeled in WCOBRAfTRAC, and Figure 1.14 a plot of the hot rod PCT elevation versus time. Note, the peak clad temperatures in Figure 1.13 are the WCOBRA/TRAC calculated temperatures, not the HOTSPOT calculated temperatures.

The R. E. Ginna LBLOCA analysis considers downcomer boiling as appropriate. The WCOBRA/TRAC computer code will determine if downcomer boiling occurs for a particular transient. If downcomer boiling is determined to occur in a transient, WCOBRA/TRAC will include the effects of downcomer boiling in the transient calculation. The worst single failure for the LBLOCA analysis is the loss of one train of ECCS injection (consistent with the ASTRUM Topical); however, all containment systems which would reduce containment pressure are modeled for the LBLOCA containment backpressure calculation. The single failure analyzed does not change with regard to the calculation of downcomer boiling or the lack thereof. A comparison of the containment backpressure utilized for the LBLOCA analysis compared to the calculated containment backpressure was previously provided in Section 2.6.6 of the R. E. Ginna Extended Power Uprate License Amendment Request (Letter from M. Korsnick to USNRC, "License Amendment Request Regarding Extended Power Uprate,/July 7, 2005). This figure has also been provided as Figure 1.15. The Best Estimate LBLOCA analysis and associated model to support the Ginna EPU are both Ginna plant-specific.

28

ATTACHMENT 3 RESPONSES TO NRC RAls REGARDING LOCA ANALYSES AUGUST 24,2005 Figure 1.1 - Pressurizer Pressure 2500 -

2000 1500-

.2 a) 5-500A 0

29

ATTACHMENT 3 RESPONSES TO NRC RAIs REGARDING LOCA ANALYSES AUGUST 24,2005 Figure 1.2 - Break Flow 35000 -

30000 -

25000 -

20000 -

E aL) 15000-0

/3 U,

0 10000-5000 -

0

-5000- , I , I I 30

ATTACHMENT 3 RESPONSES TO NRC RAls REGARDING LOCA ANALYSES AUGUST 24,2005 Figure 1.3 - Void Fraction In Pumps

-~ Intact Loop Pump

-- -- Broken Loop Pump I1-

.8 -

.6 0

C-)

U-

-0

.4

.2 -

I I I I I I I I I , I I I I I I 0 _ .

0 100 200 300 400 510 Time After Break (s) 31

ATTACHMENT 3 RESPONSES TO NRC RAls REGARDING LOCA ANALYSES AUGUST 24,2005 Figure 1.4 - Vapor Flow at Top of Core 1000 -

800 -

600-E 1 400 -

0 200 0

-200 Time After Break (s) 32

ATTACHMENT 3 RESPONSES TO NRC RAIs REGARDING LOCA ANALYSES AUGUST 24, 2005 Figure 1.5 - Total Flow at Bottom of Core 20000 -

15000 10000-U, E

a 5000 0

-5000

-10000 Time After Break (s) 33

ATTACHMENT 3 RESPONSES TO NRC RAIs REGARDING LOCA ANALYSES AUGUST 24, 2005 Figure 1.6 - Accumulator Injection Flow 2500 -

2000 -

1500-U)

E

-o v)

U-.

co 500 0

-500 I Time After Break 34

ATTACHMENT 3 RESPONSES TO NRC RAIs REGARDING LOCA ANALYSES AUGUST 24, 2005 Figure 1.7- High Head Safety Injection Flow 50 40 -

U, E 30-a) 0 0

Br

,, 20-10 I It I I , I I I I I I I I I I 0

0 100 200 300 400 500 Time After Break (s) 35

ATTACHMENT 3 RESPONSES TO NRC RAIs REGARDING LOCA ANALYSES AUGUST 24,2005 Figure 1.8 - Low Head Safety Injection Flow 200 -I 150-U, E

a) 100-0 0

50 I. I II I I I I I I I I I I I I I I I 0 _

0 100 200 310 400 500 Time After Break (s) 36

ATTACHMENT 3 RESPONSES TO NRC RAls REGARDING LOCA ANALYSES AUGUST 24, 2005 Figure 1.9 - Lower Plenum Collapsed Liquid Level 10 - _

8

'4-0f) 0~

2 0

Time After Break (s) 37

ATTACHMENT 3 RESPONSES TO NRC RAIs REGARDING LOCA ANALYSES AUGUST 24,2005 Figure 1.10 - Downcomer Collapsed Liquid Levels Broken Loop Downcomer Not Attached to o Cold Leg

-- -- Broken Loop Downcorner Attached to o Cold Leg

---

Intact Loop Downcorner Not Attached to o Cold Leg

- -- Intact Loop Downcorner Attached to a Cold Leg 30 25-20-1-

73 Q-

-o

-5 0o- '4 I 1I 1 1I 11 I

Time After Break (s) 38

ATTACHMENT 3 RESPONSES TO NRC RAis REGARDING LOCA ANALYSES AUGUST 24, 2005 Figure 1.11 - Core Collapsed Liquid Levels Low Power Channel Collapsed Liquid Level

- -- -OH/SC/SP Average Channel Collapsed Liquid Level

---

Guide Tube Average Channel Collapsed Liquid Level

-- Hot Assembly Channel Collapsed Liquid Level 12-10

-J C-04 CS 2

0*

Time After Break (s) 39

ATTACHMENT 3 RESPONSES TO NRC RAls REGARDING LOCA ANALYSES AUGUST 24,2005 Figure 1.12 - Vessel Fluid Mass 120000 -

100000 -

80000

- 0 -

6000 C-,

40000-20000 0

Time After Break (s) 40

ATTACHMENT 3 RESPONSES TO NRC RAIs REGARDING LOCA ANALYSES AUGUST 24, 2005 Figure 1.13 - Peak Clad Temperature for all 5 Rods Hot Rod

- -- - Hot Assembly

---

Guide Tubes

-- Open Holes. Support Columns. and Source Plates

- - - Low Power 2000 -

500 ll Time After Break 41

ATTACHMENT 3 RESPONSES TO NRC RAls REGARDING LOCA ANALYSES AUGUST 24, 2005 Figure 1.14 - Peak Clad Temperature Elevation for the Hot Rod 121 10 -

7I 8-0 4-a) 6-4-

2 -p . . . . . . .

0 100 200 300 4o0 500 Time After Break (s) 42

ATTACHMENT 3 RESPONSES TO NRC RAIs REGARDING LOCA ANALYSES AUGUST 24, 2005 Figure 1.15 - Analysis versus Calculated Containment Backpressure 50 -

45-35 -_

co ,,

40 -__

C20-

0) -

1..

0 0 100 200 300 400 500 Time (s) 43

ATTACHMENT 3 RESPONSES TO NRC RAls REGARDING LOCA ANALYSES AUGUST 24,2005 Core Quench Calculation In order to demonstrate stable and sustained quench, the WCOBRA/TRAC calculation time for the limiting PCT case was extended. Figure 2.1 shows the peak cladding temperatures for the five rods modeled in WCOBRA/TRAC. This figure indicates that quench occurs at approximately 50 seconds for the low power rod, 100 seconds for the core average rods under guide tubes, 375 seconds for the balance of the core average rods, and 500 seconds for the hot rod and hot assembly average rod. Once quench is predicted to occur, the rod temperatures remain slightly above the fluid saturation temperature for the remainder of the simulation. Figure 2.2 is a plot of the collapsed liquid level in the four downcomer channels and shows steady behavior, with the level in each quadrant remaining near the bottom of the cold leg. Figure 2.3 shows the collapsed liquid level in the four core channels and indicates a gradual increase in the core liquid inventory.

This is consistent with the expected result based on the removal of the initial core stored energy and the gradual reduction in decay heat. Figure 2.4 shows the collapsed liquid level in the upper plenum and indicates that there is a pool of water that has accumulated on the upper core plate.

Figure 2.5 is a plot of the vessel fluid inventory, which shows a trend of increasing vessel inventory with time after 300 seconds. This indicates that the increase in inventory due to the pumped safety injection is more than offsetting the loss of inventory through the break. Based on these results, it is concluded that stable and sustained quench has been established for the R. E.

Ginna Large Break LOCA analysis.

44

ATTACHMENT 3 RESPONSES TO NRC RAls REGARDING LOCA ANALYSES AUGUST 24,2005 Figure 2.1 - Peak Cladding Temperature for all 5 Rods Hot Rod PCT

- -- - Hot Assembly PCT

.-Guide Tube Average Channel PCT

-_-- OH/SC/SP Average Channel PCT

- -- Low Power Rods PCT 2000 -

1500 -

U-1000 -

A 11 0, III\ \

I-I--

[I lb. \

500 1 A] , II'I fir

.hL . 111 IJ I if __=->Eww I I I I I I I I I I I 0 .4 I I I I I 1 200 400 600 800 1000 1200 1i40 Time After Break (s) 45

ATTACHMENT 3 RESPONSES TO NRC RAIs REGARDING LOCA ANALYSES AUGUST 24,2005 Figure 2.2 - Downcomer Collapsed Liquid Levels Broken Loop Downcomer Not Attached to Cold Leg

- - - - Broken Loop Downcomer Attached to Cold Leg

--- Intact Loop Downcomer Not Attached to Cold Leg

-- Intact Loop Downcomer Attached to Cold Leg 30 -

25

-20

~15

-o CD

. 10 I' l Time After Break (s) 46

ATTACHMENT 3 RESPONSES TO NRC RAIs REGARDING LOCA ANALYSES AUGUST 24, 2005 Figure 2.3 - Core Collapsed Liquid Levels Low Power Chonnel Collapsed Liquid Level

-- -- OH/SC/SP Average Channel Collapsed Liquid Level

---

Guide Tube Average Channel Collapsed Liquid Level

-- Hot Assembly Channel Collapsed Liquid Level 12 10-04-C-,

2 0 200 400 600 800 1000 1200 14 00 Time After Break (s) 47

ATTACHMENT 3 RESPONSES TO NRC RAts REGARDING LOCA ANALYSES AUGUST 24, 2005 Figure 2.4 - Upper Plenum Collapsed Liquid Level Upper Plenum Inner Global Collapsed Liquid Level 10 8

6 a)

-J

.5 a'

5

.-en cn_

4 C-D o2 2

0 Time After Break (s) 48

ATTACHMENT 3 RESPONSES TO NRC RAls REGARDING LOCA ANALYSES AUGUST 24, 2005 Figure 2.5 - Vessel Fluid Inventory 120000 1 100000 80000 E

-o 60000 co) cnm Ci) 0 40000 20000

_I I I I I I I I I I I I I I 0

U 200 400 600 800 1000 1200 1400 Time After Break (s) 49