ML14189A103

Enclosure 3, Westinghouse Letter, LTR-PL-14-24, Westinghouse Responses to NRC, Donald C. Cook Unit 1 - Request for Additional Information on the Application for Amendment to Restore Normal Reactor Coolant System Pressure and Temperature.

ML14189A103
Person / Time
Site:	Cook
Issue date:	06/19/2014
From:	Westinghouse
To:	Office of Nuclear Reactor Regulation
References
AEP-NRC-2014-51, LTR-PL-14-24, TAC MF2916
Download: ML14189A103 (14)

Text

ENCLOSURE 3 TO AEP-NRC-2014-51 Westinghouse Letter, LTR-PL-14-24, "Westinghouse Responses to NRC, "Donald C. Cook Nuclear Plant Unit I - Request for Additional Information on the Application for Amendment to Restore Normal Reactor Coolant System Pressure and Temperature Consistent with Previously Licensed Conditions (TAC No. MF2916) Set #2, Part I1," dated June 19, 2014 RAIs: SCVB RAI-3(c), SCVB RAI-9(a) and SCVB RAI-9(b)

NP-Attachment (Non-Proprietary)

Westinghouse Non-Proprietary Class 3

" Westinghouse To:

Cc:

John F. Victor Christopher J. Treleani Date:

June 19, 2014 Our Ref:

LTR-PL-14-24 From: Plant Licensing Ext: 412-374-4885

Subject:

Westinghouse Responses to NRC "Donald C. Cook Nuclear Plant Unit 1 - Request for Additional Information on the Application for Amendment to Restore Normal Reactor Coolant System Pressure and Temperature Consistent with Previously Licensed Conditions (TAC.No. MF2916)"

Set #2, Part II Attachments:

1)

Reference:

1)

Westinghouse Responses to NRC, "Donald C. Cook Nuclear Plant Unit I - Request for Additional Information on the Application for Amendment to Restore Normal Reactor Coolant System Pressure and Temperature Consistent with Previously Licensed Conditions (TAC No. MF2916)"

Set #2, Part II, NP-Attachment (Proprietary)

Letter from T. J. Wengert (NRC) to L. J. Weber (Indiana Michigan Power Company), "Donald C. Cook Nuclear Plant Unit I - Request for Additional Information on the Application for Amendment to Restore Normal Reactor Coolant System Pressure and Temperature Consistent with Previously Licensed Conditions (TAC No. MF2916)," May 6, 2014 (ADAMS Accession Number: ML14099A450).

Enclosed is a copy of the Non-Proprietary (NP-Attachment) version of Westinghouse responses to Set #2, Part II of the Nuclear Regulatory Commission (NRC) Requests for Additional Information (RAIs) related to the D. C. Cook Unit I Return to Normal Operating Pressure and Normal Operating Temperature Program. Note that Attachment I contains Non-Proprietary RAI text/responses that do not contain any proprietary information and can be publicly released without any brackets or redactions.

The RAI requests/responses included from Set #2, Part II are SCVB RAI-3c; SCVB RAI-9a & 9b.

Please transmit the NP Attachment (Attachment 1) to Indiana Michigan Power Company via project letter after the appropriate releases have been processed.

If there are any questions concerning this information, please contact the undersigned.

Author:

Electronically Approved*

D. K. Solomon PL Reviewer: Electronically Approved*

F. B. Baskerville PL

• Electronically approved documents are authenticated in the electronic document management system.

02014 Westinghouse Electric Company LLC All Rights Reserved

Westinghouse Non-Proprietary Class 3 LTR-PL-14-24, NP-Attachment Westinghouse Responses to NRC, "Donald C. Cook Nuclear Plant Unit 1 -

Request for Additional Information on the Application for Amendment to Restore Normal Reactor Coolant System Pressure and Temperature Consistent with Previously Licensed Conditions (TAC No. MF2916)" Set #2, Part II SCVB RAI-3c; SCVB RAI-9a & b NP-Attachment (Non-Proprietary)

Westinghouse Electric Company LLC 1000 Westinghouse Drive Cranberry Township, PA 16066

©2014 Westinghouse Electric Company LLC All Rights Reserved NP-1

LTR-PL-14-24, NP-Attachment Response to RAI SCVB RAI-3 (c) of Set #2 Related to LOCA Containment Response Analysis SCVB RAI-3 Reference 1, Enclosure 6, Section 5.4.2.4 states:

"For the containment integrity analysis, this was completed by evaluating the effects of increased delay times for CTS actuation and containment air recirculation fan actuation on the LOCA containment integrity analysis."

(c)

As per the UFSAR Section 14.3.4.1.3.1.3, the AOR input assumption for the initial containment air temperature is 56°F in the upper and 60°F in the lower volume. Since it is: not stated that these initial condition were revised, the NRC staff assumes that the proposed analysis used the same initial temperatures. Please provide justification that these initial temperatures are conservative and would maximize the peak containment pressure and temperature transients compared to the transient obtained by using the initial TS 3.6.5 maximum value of 100F in the upper volume and 120°F in the lower volume.

Response

In preparing the response to SCVB RAI-3 (c), it was found that the impact of the NOP/NOT changes on peak containment pressure presented in Sections 5.4.2.5, Results, and 5.4.2.6, Conclusions, of Reference 1 Enclosure 6 is incorrect relative to changes in containment air recirculation fan delay and CTS delay. As a result, a replacement for the text in Section 5.4.2.5 and 5.4.2.6 is provided following this paragraph for your convenience. Changes to containment pressure values are identified in brackets.

5.4.2.5 Results The key parameters assumed in the LOCA M&E AOR are compared below with the parameters developed to support Cook Unit 1 NOP/NOT. In all cases, the AOR values remain bounding. The RCS temperatures below for AOR and NOP/NOT both include uncertainties of 5.1 F. The secondary pressure and temperature values ore the high safety analysis values provided with the NSSS design parameters.

Core stored energy is provided as a bounding value, and no additional uncertainty is applied in the LOCA M&E analysis.

Parameter AOR NOP/NOT Vessel Inlet Temperature (OF) 552.5 548.7 Vessel Outlet Temperature (*F) 620.3 614.2 Core Inlet Temperature (*F) 552.5 548.7 SG Secondary Pressure (psia) 878 870 SG Secondary Temperature (°F) 529.1 527.9 Core Stored Energy (full power seconds) 4.95 4.76 NP-2

LTR-PL-14-24, NP-Attachment The evaluation indicated that the effect of the containment air recirculation fan delay as well as the CTS delay resulted in a pressure increase of [0.0486] psi. The AOR peak containment pressure is 11.6884 psig and the combined effect of CTS and containment air recirculation fan delays results in a peak containment pressure of [11. 737] psig.

5.4.2.6 Conclusions Subsection 5.4.2.5 indicates that the NSSS design parameters supporting the Cook Unit 1 LOCA M&E AOR are bounding relative to the NOP/NOT NSSS design parameters. It is concluded that the NSSS design parameter inputs are conservative and operation at NOP/NOT is supported.

The core stored energy in the Cook Unit 1 LOCA M&E AOR, 4.95 full power seconds, is-greater than the value calculated for NOP/NOT (including effects of thermal conductivity degradation) of 4.76 full power seconds. It was concluded that the fuel modeling in the AOR supports operation at NOP/NOT.

There was no impact due to an increase in the low pressurizer pressure reactor trip nominal setpoint since rod drop is not credited in the LOCA M&E release calculations (the core shuts down due to voiding).

It is concluded that the AOR calculations for Cook Unit 1 LOCA M&E support operation at NOP/NOT.

Sensitivity studies showed that the effect of the CTS and containment air recirculation fan actuation delays was a containment peak pressure increase to [11.737] psig which is acceptable for containment integrity because the containment design limit of 12 psig is not exceeded.

The evaluation of the long-term LOCA M&E and peak containment pressure is predicated upon the continued application of the operability assessment supporting NSAL-11-5 (Reference 3), in conjunction with the AOR.

In direct response to the RAI question on initial temperature in the upper and lower containment compartments, a review found that it was originally determined that the initial containment temperatures are biased low because of the density effect on air mass function; however, more recent analysis has determined that it is also influenced by the timing of ice bed meltout, which is affected by initial ice mass, containment spray operation and energy content of the mass and energy release. The analysis of record presented in UFSAR Section 14.3.4.1.3.1.3 (based on initial temperatures biased low) results in a maximum calculated containment pressure of 11.69 psig (includes adjustments).

In response to RAI-3 (c), a sensitivity analysis was performed using the D. C. Cook LOTIC1 (Reference 3) containment model for the AOR case and assuming the maximum Technical Specification (TS) 3.6.5 (a)

(b) maximum value of 100°F in the upper volume and 120°F in the lower volume.

The input model was revised to reflect containment initial air and heat slab temperatures based on the technical specification maximum values. The resulting peak containment pressure was higher than the analysis of record (AOR) case.

The results of the sensitivity indicate the calculated containment pressure would increase 0.72 psi to 12.41 psig (includes adjustments). Further, the addition of the effects of the containment air recirculation fan (CEQ) delay as well as the CTS delay would result in a peak containment pressure of 12.46 psig. This elevated pressure exceeds the containment design pressure limit of 12 psig specified in the D. C. Cook Unit 1 and 2 TS Basis B 3.6.4 Containment Pressure.

NP-3

LTR-PL-14-24, NP-Attachment Conservatism exists in the Westinghouse LOCA M&E methodology (Reference 4) to justify that a substantial safety hazard (SSH) could not exist. These conservatisms are presented in Reference 4, Section 5.1, "Model Conservatisms," which has been approved by the United States Nuclear Regulatory Commission (U.S. NRC). The NRC's Safety Evaluation Report (SER) is attached at the beginning of Reference 4. Reference 4 has shown that the conservatisms in the LOCA M&E methodology result in an increase in the calculated containment pressure that is on the order of 6 or more psi greater than what would be calculated using less conservative LOCA M&E releases. It is noted that approximately 2.8 psi of the 6 psi margin was used in the Reference 5 notification. (Subsequent Cook-specific sensitivity runs have further refined the 2.8 psi penalty from Reference 5 to a Cook-specific value of 2.31, as further described in the response to SCVB RAI-5(b).) Thus, there is still 3.2 psi of conservatism that can be used to offset the use of the non-conservative containment initial air temperature bias application.

Therefore, the containment structural integrity will not be challenged and this issue could not create a SSH if it were left uncorrected. Note, results relative to the generic pressure penalty supplied in NSAL-14-2 (Reference 6) continues to be applicable.

Additionally, to supplement the generic operability evaluation, described above, either one of two independent actions can be taken to mitigate the containment pressure increase due to the impact of the elevated compartment temperature input.

Relax RHR containment spray actuation time from 4500 seconds to 4200 seconds. Sensitivity studies have shown this will provide approximately one psi of pressure relief for the conditions generated above. The results of the sensitivity indicate the calculated containment pressure would be 11.29 psig (includes adjustments). Further, the addition of the effects of the containment air recirculation fan (CEQ) delay as well as the CTS delay would result in a peak containment pressure of 11.34 psig.

Or, Credit available ice in ice condenser above technical specification minimum. (Projected additional ice mass 25,000 Ibm). Sensitivity studies have shown this will provide approximately 0.7 psi of pressure relief for the additional initial ice mass credit or a calculated peak containment pressure of 11.72 psig (includes adjustments). Further, the addition of the effects of the containment air recirculation fan (CEQ) delay as well as the CTS delay would result in a peak containment pressure of 11.77 psig.

In summary, the penalty for to the initial condition assumption for the'containment air temperature has been assessed against the generic margin communicated in NSAL-11-5, the excess ice contained within the ice condenser, and relaxation of RHR containment spray actuation and each separate source is sufficient to offset the penalty as identified above.

NP-4

LTR-PL-14-24, NP-Attachment References

1.

WCAP-17762-NP, Revision 1, "D. C. Cook Unit 1 Return to Reactor Coolant System Normal Operating Pressure/Normal Operating Temperature Program - Licensing Report,"

September 2013.

2.

Letter from Thomas J. Wengert (NRC) to Lawrence J. Weber (SEP), "Donald C. Cook Nuclear Plant, Unit 1 - Request for Additional Information on the Application for Amendment to Restore Normal Reactor Coolant System Pressure and Temperature Consistent with Previously Licensed Conditions (TAC No. MF2916)," May 6, 2014.

3.

WCAP-8354-P-A (Proprietary), "Long Term Ice Condenser Code - LOTIC Code," April 1976.

4. WCAP-10325-P-A (Proprietary), "Westinghouse LOCA Mass and Energy Release Model for Containment Design March 1979 Version," May 1983.

S.

NSAL-11-5, "Westinghouse LOCA Mass and Energy Release Calculation Issues," July 2011.

6.

NSAL-14-2, "Westinghouse Loss-of-Coolant Accident Mass and Energy Release Calculation Issue for Steam Generator Tube Material Properties," March 31, 2014.

NP-5

LTR-PL-14-24, NP-Attachment Response to RAI Set #2 for the D. C. Cook Unit 1 NaP/NOT Program Related to SLB Containment Response Analysis SCVB RAI-9 "Reference 1, Enclosure 6, Table 5.5.2.2:

(a)

The input assumption in the seventh bullet states the containment upper volume initial temperature as 57°F. By a sensitivity analysis, please justify that this initial condition is conservative and would maximize the peak containment temperature transient compared to the transient obtained by using the initial TS maximum value of 120°F.

(b)

By sensitivity analysis, please justify using initial containment upper volume temperature of 57°F would maximize the peak containment pressure transient compared to the transient using the initial TS maximum value of 120YF."

Response

In preparing the response to SCVB RAI-9, it was found that the seventh bullet in Section 5.5.2.2 of to Reference 1 only provides the set of input parameters (ambient temperatures, pressures, and relative humidity) for the double-ended ruptures (DERs) that were analyzed for NOP/NOT and does not identify the changes to these inputs that are unique to the split breaks. Historically, some of the input parameters for these two break types are different to ensure limiting results. For example, past sensitivity studies have found that high relative humidity is conservative for the split breaks while low relative humidity is conservative for the DERs. As a result of this finding, a replacement for the bulleted information is provided following this paragraph. This information will help put the responses to RAI-9 Parts (a) and (b) in proper perspective.

"The initial conditions in the containment are a temperature of 120F in the lower compartment, 1207F in the dead-ended compartment, a temperature of 557F (for the DERs) or 577F (for the split breaks) in the upper compartment, and a temperature of 5F (for the DERs) or 277F (for the split breaks) in the ice condenser. All containment volumes are at a pressure of 0.3 psig and a relative humidity of 15 percent (for the DERs) or 100 percent (for the split breaks), with the exception of the ice bed, which is 100 percent relative humidity for all cases.

SCVB RAI-9 (a) - Sensitivity of the Upper Containment Temperature on SLB Peak Containment Temperature The response to SCVB RAI-9 (a) is presented in two subsections that follow. The first addresses the impact of an elevated upper containment initial temperature on the limiting split break and the second examines the impact on two DERs, all of which are identified in Table 5.5.2-1 of Enclosure 6 to Reference 1.

Impact on the Limiting Split Break The limiting SLB containment temperature response for NOP/NOT is identified in Table 5.5.2-1 of to Reference 1 as the 100.34% power, 0.865 ft2 split break with an MSIV Single failure. This break yields a peak lower containment temperature of 324.670F. In response to RAI-9 (a), a sensitivity analysis was performed for this limiting break using the D. C. Cook Unit 1-specific containment model and assuming the maximum Technical Specification (TS) 3.6.5a upper compartment temperature of 100°F.

[Note that RAI-9(a) refers to a maximum temperature of 120°F; however, this higher limit only applies to the lower containment, as indicated in TS 3.6.5b.] The initial containment temperature input NP-6

LTR-PL-14-24, NP-Attachment parameters for the base and sensitivity cases are presented in Table 1 [all other inputs remain unchanged] and the containment temperature transients for both cases are provided in Figure 1.

Table 1 Limiting SLB Split Break and Associated Sensitivity Case for Elevated Upper Containment Temperature Input Parameter Comparisons Initial Coni nment Temperatures (F)

- Maximum Lower Case Uper

>Lower Deadi End Containment Heat Air Heat Air Heat Air Temperature (F)

Heats Sinks Sinks________

Base

[100.34% power, 0.865 ft2 split 60 57 120 120 None 120 324.67 break with an MSIV single failure]

Sensitivity Increased Upper Containment 100 100 120 120 None 120 324.96 Temperature Figure 1 Lower Compartment Temperature Transient Comparison low (60F) initial temperature high (101F) initial temperature 05) o200 E

T060 N0 1000 0

Time (sec)

As shown in Figure 1, the effects on the lower compartment temperature due to the increase in initial upper containment temperatures are minimal, both from the peak and overall temperature transient perspectives. A review of the numerical output did, however, indicate a slight increase in peak temperature of 0.3°F to a value of 324.96°F. The change in the peak temperature is not discernible on Figure l and clearly represents an intermittent temperature spike. Nevertheless, this elevated temperature exceeds the current 324.7°F maximum containment temperature limit specified in TS Basis B3.6.5, Containment Air NP-7

LTR-PL-14-24, NP-Attachment Temperature. As a result, the next paragraphs describe actions taken to offset the impact of the elevated upper containment temperature input with a reduction in the very conservative input value assumed for the initial relative humidity in containment.

The current conservative initial relative humidity input used in the split SLB analyses for D.C. Cook Unit 1 is identified as 100% RH [see the new information provided immediately following the first paragraph of this response to SCVB RAI-9]. In response to the findings in the previous paragraph, AEP provided documentation supporting a maximum value of 65% for the initial relative humidity in containment during power plant operation. Using this new information, a second set of sensitivity analyses for the split SLBs for NOP/NOT was performed during which the conservative 100% initial relative humidity input was reduced in increments to determine the parameter's effects on both the containment temperature and pressure responses. The containment temperature and relative humidity input values for the base and sensitivity cases are presented in Table 2 [all other inputs remain unchanged], as are the peak containment temperature and pressure results.

Table 2 Limiting SLB Split Break and Associated Sensitivity Cases Elevated Upper Containment Temperature and Relative Humidity Changes Input Parameter Comparisons Initial Containment Temperatures (°F)

Maximum Lower Upper Lower Dead End Containment Case Conditions Heat Heat Heat Sinks Air Sinks Air Sinks Air Temp.

Press

(°F)

(psig)

Base(l)

[100.34% power, 0.865 ft2 split 60 57 120 120 None

ý120 324.67 6.77 break with an MSIV single failure]

Sensitivity 1 100% RHI(21(3) 100 100 120 120 None 120 324.96 7.00 Sensitivity 2 75% RH(2)(3) lob 100 120 120 None 120 323.95 6.58 Sensitivity 3 60% RHS(2)(i) 100 100 120 120 None 120 324.04 6.56 Sensitivity 4 50% RHS(2)(3) 100 100 120 120 None 120 324.12 6.84 Table 2 Notes:

(1) The Base Case assumes 100% relative humidity in the upper, lower, and dead-end compartments. It also assumes low initial temperatures in the upper containment.

(2) Sensitivity Case Nos. 1-4 assume maximum temperature in the upper containment.

(3) Sensitivity Case Nos. 2-4 assume reduced values from the Base Case for relative humidity for the upper containment. The lower compartment and the dead-end compartment relative humidity are unchanged at 100% for all Sensitivity Cases.

The transient results for Sensitivity Case Nos. 2-4 in Table 2 show that reductions in the assumed initial relative humidity to <75% in the upper compartment completely offset the adverse effects on the split break maximum containment temperature from the initial assumed ambient temperature increase to 100°F in the upper compartment.

NP-8

LTR-PL-14-24, NP-Attachment Impact on the Limiting DER Although the split SLBs are limiting for the NOP/NOT Program, the two most limiting DER SLB containment temperature response cases from Table 5.5.2-1 of Enclosure 6 to Reference 1 were also examined for the impact from elevated upper containment temperature initial conditions. These are the small 1.0 ft2 DER at 0% power with an MSIV single failure, which has the highest peak temperature for all DERs analyzed, and the large 1.4 ft2 DER at 30% power with an AFW runout control single failure, which has a high peak temperature immediately following the initial blowdown. The small DER has a relatively "late" peak temperature for the SLB transient. In response to RAI-9(a), a sensitivity analysis was performed for the limiting DERs using the D. C. Cook Unit 1-specific containmentmodel and assuming the maximum TS 3.6.5a upper compartment temperature of 1000F. The containment temperature input values for the base and sensitivity cases are presented in Table 3 [all other inputs remain unchanged], as are the peak containment temperature and pressure results.

Table 3 SLB Limiting DERs and Associated Sensitivity Cases Elevated Upper Containment Temperature Changes Input Parameter Comparisons Initial Containment Temperatures (°F)

Maximum Lower Upper Lower Dead End Containment Case(1)

Conditions Heat Heat Heat Sinks Air Sinks Air Sinks Air Temp.

Press

(°F)

(psig)

Base Case #1 324.49 8.31 @

[0% power, 1.0 ft2 DER with an 60 55 120 120 None 120 20.22 MSIV single failure]

se.

sec Sensitivity 1 323.26 8.00 @

[Increased Upper Containment 100 100 120 120 None

ý120 236.0 18.39 Temperature]

sec sec Base Case #2 324.35 9.72 @

[30% power, 1.4 ft2 DER with an 60 55 120 120 None

120 1

2.46 12.36 AFW runout control single failure]

sec sec Sensitivity 2 324.14 9.67 @

[Increased Upper Containment 100 100 120 120 None 120 12.36 2.46 Temperature]

sec sec Table 3 Note:

(1) All Cases in Table 3 assume 15% relative humidity in the upper, lower, and dead-end compartments.

The sensitivity results for the two limiting DER SLBs in Table 5.5.2-1 of Enclosure 6 indicate that, when the initial upper compartment ambient and heat sink temperatures are increased to 100°F, the lower containment peak temperatures decrease. In addition, peak pressures in the lower compartment are relatively insensitive to upper containment temperature increases showing a slight reduction.

NP-9

LTR-PL-14-24, NP-Attachment SCVB RAI-9 (b) - Sensitivity of the Upper Containment Temperature on SLB Peak Containment Pressure As indicated previously in the response to SCVB RAI-9(a), the limiting SLB containment temperature response for NOP/NOT is identified in Table 5.5.2-1 of Enclosure 6 to Reference I as the 100.34% power, 0.865 ft2 split break with an MSIV single failure. The two most limiting DER.SLB containment temperature response cases are the small 1.0 ft2 DER at 0% power with an MSIV single failure and the large 1.4 ft2 DER at 30% power with an AFW runout control single failure. In response to RAI-9(a) and (b), sensitivity analyses were performed for these limiting breaks using the D. C. Cook Unit 1-specific containment model and assuming the maximum TS 3.6.5a upper compartment temperature of 100°F.

Impacts on the peak lower containment temperature and pressure are presented in Tables 2 and 3 in the response to RAI-9(a). Impacts on the lower containment pressure transients for the limiting split break and the two most limiting DERs from RAI-9(a) are provided in Figures 2, 3 and 4, respectively, and are described in the next paragraph.

Comparison of the lower containment pressure transients in Figure 2 for the 60°F and 100°F initial upper containment temperatures indicates that a higher initial temperature in the upper containment is slightly more conservative for both the short-term pressure transient and the peak pressure for the split break; however, it is less conservative for the longer-term transient. The short-term pressure transients including the peak pressures and the longer-term transients for the small 1.0 ft2 DER at 0% power case and the large 1.4 ft2 DER at 30% power case are less limiting assuming the 100°F initial upper contain-ment temperature compared to the 60OF initial containment temperature. Figure 3 presents the comparison for the small 1.0 ft2 DER at 0% power SILB and Figure 4 shows the comparison for the large 1.4 ft2 DER at 30% power SLB. Regardless, as indicated in Section 5.4.2.6 of Enclosure 6 to Reference 1 and in Figures 2 and 3 of this response, the containment pressure response for LOCA is more limiting with respect to the design pressure limit than the containment pressure response for SLB. It is for this reason that the initial conditions for the SLB containment analysis are defined to maximize the transient temperature and not the transient pressure response.

NP-10

LTR-PL-14-24, NP-Attachment Figure 2 Lower Compartment Pressure Transient Comparison low (60F) initial temperature high (rOOF) initial temperature Li) a-Co Co a) 0 200 400 600 800 Time (sec) 1000 Figure 3 Lower Compartment Pressure Transient Comparison low (60F) initial temperature high (102 F) initial temperature Co a-a)

Co Co a) 0~

0 200 400 600 800 Time (sec) 1000 NP-11

LTR-PL-14-24, NP-Attachment Figure 4 Lower Compartment Pressure Transient Comparison low (60F) initial temperature high (0O1F) initial temperature Cs, G)

Co 4) 0~

0 200 400 600 800 Time (sec) 1000 Summary Resronse to SCVB RAI-9(a) and (b)

Results of the sensitivity analyses demonstrate that the combination of the assumed input values for the initial upper compartment temperature (57°F) and the conservative initial relative humidity (100%) inside containment for the split breaks produces a lower compartment temperature that conservatively meets the maximum containment temperature acceptance criterion. The assumptions of a 100°F value for the initial upper compartment temperature (TS maximum) and a plant-specific maximum initial relative humidity of 65% inside containment (atthe maximum temperature) produce less limiting lower compart-ment temperatures. For the DER SLBs, the sensitivity analyses show that the assumption of a 100°F value for the initial upper compartment temperature produces less limiting lower compartment temperatures.

Peak temperature results documented in Table 5.5.2-1 of Enclosure 6 remain valid and conservative.

Results of the sensitivity analyses demonstrate that the maximum TS value for the initial upper compartment temperature (100°F) produces a minimal change in the early peak pressure and a decrease in the long-term pressure transient. Notwithstanding that finding, the containment pressure transient for the LOCA defines the limiting pressure response and easily bounds the pressure responses for a SLB.

For this reason, the initial conditions for the SLB containment analysis are defined to maximize the transient temperature and not the transient pressure response. Regardless of the initial conditions defined for the containment model, the peak pressure results documented in Table 5.5.2-1 of remain reasonable and not limiting with respect to the design pressure limit.

NP-12