NSD-NRC-97-5024, Provides W Responses to Items Discussed in NRC Ltr .Attachment Includes Dates for Completion of Certain Analytical Activities Re AP600 Design Changes Addressing Post 72 H Actions.Nrc Comments Requested by 970331

Provides W Responses to Items Discussed in NRC Ltr .Attachment Includes Dates for Completion of Certain Analytical Activities Re AP600 Design Changes Addressing Post 72 H Actions.Nrc Comments Requested by 970331

ML20137C689
Person / Time
Site:	05200003
Issue date:	03/14/1997
From:	Mcintyre B WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:	Quay T NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NSD-NRC-97-5024, NUDOCS 9703250086
Download: ML20137C689 (18)

Text

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Westinghouse Energy Systems Ba 3ss Pittsburgh Pennsylvania 15230-0355 Electric Corporation NSD-NRC-97-5024 DCP/NRC0773 Docket No.: STN-52-003

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March 14,1997 Document Control Desk Nuclear Regulatory Commission Washington, DC 20555 ATTENTION: T. R. Quay

Subject:

AP600 DESIGN CIIANGES TO ADDRESS POST 72 IIOUR ACTIONS

Dear Mr. Quay:

j In a February 4,1997, meeting with NRC staff, Westinghouse presented AP600 design changes to meet the NRC staff position on post 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> actions, as approved by the staff requirements memorandum on SECY-96128, dated January 15,1997. In NRC letter, Thomas T. Martin to Nicholas J. Liparulo, dated February 18,1997, NRC staff provided results of their preliminary assessment of the AP600 design changes.

The attachment provides the Westinghouse responses to the items discussed in the NRC letter. The attachment includes dates for completion of certain analytical activities. These dates are consistent with the schedule in SECY-97-051 for Westinghouse activities to achieve an FSER in November,1997.

Revision 11 to the AP600 SSAR included descriptions of the changes to the plant discussed at our February 4,1997, meeting for staff review.  ;

1 The NRC is requested to review the attached material and provide any further comments to Westinghouse by l March 31,1997. Please contact Mr. Ron Vijuk (412)374-4728, if you have any questions concerning this material.

Sincerely yours, A

Brian A. McIntyre, Man lager 7 l

Advanced Plant Safety and Licensing rpv/ cmp p" C O 'i 1 i l

{R03250086 970314 ADOCK 05200003 Attachment kJUUA . PDR , _

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cc: N. J. Liparulo, Westinghouse (w/o attachment)

A. lxvin, NRC/NRR (w/ attachment)

T. Martin, NRC/NRR (w/ attachment) we .@N.U.0

AttNhment to NsD-NRC 97-5024 DCP/N RC0773 Docket No.: sTN-52-003

, Page 1 T

Westinghouse Responses to NRC Concerns NRC Concern:

Based on a preliminary assessment of the proposed AP600 design changes, the staff has several concerns:

(a) Although the addition of a seismically qualified 7 day supply of makeup water for the spent fuel pool along with the backup cooling protection from the RNS appears to represent an improvement to the current AP600 ; pent fuel pool caoling system design, and may meet the stalT's post-72 hour action policy, it is stillless rolaust than many operating plant designs. In addition, the spent fuel pool ventilation and filtration (HVAC) system is not seismically qualified as recommended in the Standard Review Plan (SRP) in order to meet the requirements of GDC 2. Westinghouse considers that tFis is acceptable since no credit is taken for the SFP IIVAC system in mitigating the offsite dose rates which Westinghouse helieves will be a small fraction of 10 CFR Part 20. This will need to be verified.

Westinghouse Response:

The AP600 spent fuel pool cooling capability is very robust. The combination of nonsafety-related active features and safety-related passive features in AP600 for spent fuel pool cooling result in an extremely low likelihood of exposing the public to harmfu! releases from a failure to cool the spent fuel. The AP600 design changes improve the non-safety related active features by providing backup capability to the Spent Fuel Pool Cooling System (SFS) via cross connect piping from the Normal Residual Heat Removal System (RNS), and improve the passive safety-related features by providing additional gravity driven, safety-related water makeup to last for at least 7 days following an event.

The AP600 design meets SRP guidance by providing a makeup water system, water sources and a fuel pool building which are Seismic I. and by meeting 10CFR20 dose limits without credit for ventilation and filtration systems. Westinghouse is performing analyses on this basis which are expected to verify that the offsite dose rates are a fraction of the 10CFR20 dose limits. These analyses will be available for NRC review by March 28,1997.

NRC Concern:

(b) Of particular concern to the staff is the proposal by Westinghouse to open the main control room doors after 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and rely on natural circulation ventilation and cooling for plant operators and instrumentation and control systems. This could result in exposing plant operators to a potentially harmful environment generated by the boiling of the spent fuel pool (e.g steam, radiological elements). In addition, opening the control room doors compromises any protection from toxic gas releases which the control room is designed to protect against.

Consequently, the staff cannot conclude that the Westinghouse proposal meets the requirements of GDC 19 for protection of control room operators from environmental hazards. Westinghouse will need to provide additional justification for its current position, addressing the concerns identified above, or an alternative approach for assuring adequate protection of control room personnel.

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Attachment to NsD-NRC-97-5024 l . DCP/N RC0773 j , Docket No.: STN-52-003 ,

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Page 2 Westinghouse Responses to NRC Concerns  :

1 Westinghouse Response:

Westinghouse has decided to add small ancillary fans to provide MCR and I&C room ventilation in the post j 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> period. This avoids complex analyses to determine natural ventilation and these fans are small i loads on the 15 kW ancillary diesels. Ventilation maintains the MCR in a habitable condition and is expected to result in personnel exposures less than 5 rem total effective dose equivalent, as required by t GDC 19.

I j Analysis is being performed to determine operator GDC 19 dose including effects from spent fuel pool )

d boiling coincident with a LOCA and is expected to show that the dose limit is not exceeded when MCR i doors are assumed open at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. This analysis will be available for NRC review by April 18, 1997.

The analysis considers that spent fuel pool evaporation is vented from the fuel handling area to the outside environment via a blowout panel. The panel is located along the east wall of fuel handling area south of

the annex building. There is no internal pathway between the radiologically controlled area and I

nonradioactive portions of the auxiliary building via the annex building. The ancillary powered fan draws outside air from the air intake opening located on the roof of the auxiliary building. This airflow path precludes a significant volume of air from infiltrating into the MCR from locations other than the intake opening on the roof of the auxiliary building. Providing ventilation to the MCR with outside air maintains 4

the MCR environment near the average outdoor air temperature, j Accidents involving the release of toxic chemicals from nearby mobile and stationary sources is a site i specific accident category that will be considered in determining the frequency of occurrence by the l Combined License applicant as specified in SSAR Chapter 2. Compliance with NRC R.G. l.78 and R.G.

) 1.95 will be discussed on a site specific basis, j Current plants with active control room HVAC systems incorporate design features to cope with hazardous chemicals and chlorine gas releases in compliance with NRC R.G.1.78 and R.G.1.95. Gas analyzers in the control room air intakes isolate the control room from the outside and the HVAC system operates in complete recirculation mode. Should a specific site require this protection, the AP600 nonsafety-related

! HVAC system can provide it in a similar manner as current plants. The AP600 safety-related Control Room Emergency Habitability System (VES) provides another level of defense with the capability to supply air to the MCR for at least 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> considering a single failure. Without the single failure, or if the failure

is repaired within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, the operator can adjust the air flow to maintain MCR pressurization for 144 hours0.00167 days <br />0.04 hours <br />2.380952e-4 weeks <br />5.4792e-5 months <br />. A combination of a seismic or hurricane event together with a core damage source term in contr inment, a toxic gas release in the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 7 day time window, failure of non-safety related HVAC extendn.g beyond 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, and failure of one train of safety-related VES is considered beyond the design basis for MCR toxic gas release protection.

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, Attachment to NSD-NRC-97-5024 DCP/N RC0773 Docket No.: STN-52-003 l

, Page 3 !

Westinghouse Responses to NRC Concerns l

l NRC Concern:

(c) In order to contain the additional 150,000 gallons of water in the PCS storage tank, j Westinghouse proposed to change the design of the PCS tank by (1) increasing the maximum water level from Elevation 298 ft. to 303 ft., (2) raising the top of the tank by one foot, (3) reducing the thickness of the tank room from 24 inches to 15 inches, (4) decreasing the thickness of the inner tank wall from 24 inches to 18 inches, and (5) adding a 9 inch deep fire water tank composed of two stainless steel plates underneath the PCS tank roof. From these design changes, Westinghouse estimated that the affected mass decreases by 2 percent in the horizontal direction and increases by 5 percent in the vertical direction. From this estimated effect, Westinghouse concludes that these changes are small enough that they will have negligible effect on the global seismic analyses of the nuclear island structures, and will only have small effects on the structural design of the shield building roof. The design calculations for the shield building roof for the local seismic analyses are currently being updated by Westinghouse. These new design calculations will include, (1) a 3D finite element analysis of the roof used to develop the equivalent stick model used in the global nuclear island seismic j analysis, (2) a dynamic sloshing analysis with increased inventory, (3) a design calculation of l the shield building roof, (4) a concrete outline and reinforcement drawings, and (5) a seismic margin evaluation of roof structures, which will be available for staff review when complete.

Based on the presentation by Westinghouse and the staff's discussion with Westinghouse during the February 4,1997 meeting, Westinghouse needs to justify its conclusion that the ,

global effect of the design change is negligible by appropriate calculations and evaluation, i From the staff's engineering judgement, the design changes of the PCS tank will raise the height of the roof structure centroid and, in turn, will affect the rocking and translational responses (seismic shear forces, bending moments and in-structure response spectra) during a seismic event. The staff also believes that the design changes to the roof structures will affect j the design of the nuclear island foundation mat. l l

Westinghouse Response:

As described during the February 4,1997 meeting, Westinghouse has initiated appropriate calculations and l evaluation to support our judgement that the global effect of the design change is negligible. These tasks and their schedule are described in the responses to the staff comments 11,12 and 13.

?nt LP

. Attachment to NSD-NRC-97-5024 DCP!N RC0773 Dxket No.: STN-52-003 Page 4 Westinghouse Responses to NRC Comments Containment Systems Comments NRC Comment:

1 There are two areas related to post-72 hour action design changes that affect the containment systems 4

branch review: (a) the PCCSWT capacity was increased by 150,000 gallons (from its current 400,000 ,

, gallon capacity), and (b) an additional stand pipe was added to provide four periods of flow, instead i of the current three periods. The fourth and final phase (72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 7 days) provides about 18 gpm flow to cool containment. Westinghouse needs to address the following questions:

(1) There is no known data at 18 gpm to support a water coverage fraction for use in IVGOTIIIC.

l The minimum imown test data is for an equivalent value of about 50 gpm, from the cold 4

water distribution tests.

Westinghouse Pesponse:

Subsequent to the February 4,1997, meeting, Westinghouse has decided to provide an additional water tank for PCS makeup in the post-72 hour period. This tank is located at grade level and is analyzed to show it will withstand an SSE and a 145-mile-per-hour wind. The PCS recirculation pumps described at the ,

i meeting take suction from this tank for the post 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> period and supply makeup flow to the PCCWST to supplement its initial inventory. A sketch of the PCS including this additional tank is provided at the end of this attachment. Standpipe elevation / orifice size are adjusted to account for this additional water inventory J in the post 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> period and maintain flow onto the containment vessel consistent with achieving

) sufficient coverage and heat removal to maintain containment pressure below 50 percent of design pressure j during the 3 to 7 day period. The grade level tank is sized such that the flow rate onto the containment i

shell in the 3 to 7 day period is maintained at or above the minimum corresponding value from the cold water distribution tests. Additional description, including SSAR markups, of the additional tank will be available for NRC review with the WGOTHIC analysis identified in the response to NRC Comment 2.

NRC Comment:

(2) A preliminary WGOTHIC prediction indicates that after 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> with the 18 gpm flow rate, the pressure will rise above the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> criteria used by Westinghouse (50 percent of design pressure). It is not clear if this represents a change in the Westinghouse acceptance criteria for the PCCS performance.

Westinghouse Response:

The preliminary WGOTHIC analysis was based on PCS flow rates greater than 50 gpm for the first 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Although the preliminary analysis showed the containment pressure above 50 percent design pressure during part of the 24 to 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> period, it does not represent a change in acceptance criteria and was found to be a result of erroneous code input. WGOTHIC analysis with correct input is being performed and will be available for NRC review by April 18. 1997. The acceptance criteria of maintaining the contaiament pressure below 50 percent of design pressure is retained.

411P

Attachment to NSD-NRC-97-5024 DCP/NRC0773

, Docket No.: STN-52-003 Page 5 Westinghouse Responses to NRC Comments Reactor Systems Branch Comments NRC Comment:

(3) Are any changes to the at power or shutdown ERGS necessary in light of these design changes?

Westinghouse Response:

No changes to power or shutdown ERGS are necessary for the post-72 hour design changes. Long term

actions such as those associated with post-72 hour scenarios are dealt with in the accident management plan for the site rather than ERGS or emergency operating procedures.

Radiation Protection Branch Comments NRC Comment:

(4) In addition to the offsite radiological consequence assessment, Westinghouse should also assess the main control room operator doses due to the spent fuel pool boiling after 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and up to 30 days. Iodine partition factor of 100 used by Westinghouse for offsite radiological consequence assessment is not acceptable to the staff since pool water level (could be as low as 2 feet) does not warrant such a partition factor. Westinghouse should provide the offsite and control room radiological consequence analyses for our review.

Westinghouse Response:

Analyses are being performed for both offsite doses and for MCR operator doses considering spent fuel pool boiling out to 30 days. These analyses will be available for NRC review by March 28.1997, including justification for the iodine partition factor in the pool. The results are expected to show that dose criteria are not exceeded.

NRC Comment:

(5) Westinghouse stated that the radiological consequence analysis is currently being performed for design basis accidents in Chapter 15 for opening the control room after 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> into the accident. Westinghouse should provide the offsite and control room operator dose assessment for the time period of the accident (30 days) for our review. The staff notes that Westinghouse cited 10CFR20 limits when discussing operator doses in the main control room.

The staff believes that GDC 19 is the applicable regulation in this instance. Westinghouse should also clarify the regulatory bases being applied to the radiological releases associated with spent fuel pool boiling.

Westinghouse Response:

The offsite and MCR dose assessments being performed will cover the 30 day time period. Westinghouse agrees that GDC 19 is the applicable regulation for MCR operator doses, and that 10CFR20 is the applicable regulation for offsite doses following a loss of spent fuel cooling event (not coincident with an accident).

2M tP

, Attachment to NSD-NRC-97-5024 DCP'N RC0773 Docket No.: STN-52-003 Westinghouse Responses to NRC Comments Plant Systems Branch Comments NRC Comment:

In consideration of possible spent fuel pool boiling and its relationship to main control room habitability, the Plant Systems Branch has some additional concerns regarding the main control room habitability system.

(6) Current operating reactors have comparatively much larger unfiltered in-leakage problems than assumed for the AP600. The VES design in-leakages are not verified through periodic testing in accordance with AST51 E741, " Standard Test hiethod for Determining Air Leakage Rate by Tracer Dilution".

1 Westinghouse Response:

4 htCR operator dose analyses are being performed including consideration of releases from spent fuel pool boiling. These analyses will be available for NRC review by March 28,1997, and are expected to show i that MCR operator dose limits are not exceeded.

l In-leakage to the MCR during VES operation (0-72 hours) is controlled by maintaining a positive pressure in the MCR and with a vestibule style entrance which restricts the volume of containment air that can enter l the MCR as a result of ingress and egress. The in-leakage assumed in the MCR dose ana'yses is due to I ingress / egress and is conservatively estimated. The MCR pressure envelope on AP600 is more leak tight  !

than current operating plants because of fewer electrical cable penetrations and a passive habitability system

, which allows the HVAC supply, exhaust and return air ductwork penetrating the MCR to be isolated. The MCR pressurization capability is tested every 24 months in accordance with Technical Specification Section l

. 3.7.6.8. This precludes the need for AP600 testing according to ASTM E741, which is more suited to active HVAC systems. Between 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and 30 days, MCR habitability is evaluated assuming that the MCR is ventilated with outside air, in this mode of operation, the MCR and auxiliary building personnel

, access doors are opened to provide a path for the ventilation air to exfiltrate from the MCR into the annex building.

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. Attachment to NSD-NRC-97-5024 DCP/NRC0773 Docket No.: STN-52-003 Page 7 Westinghouse Responses to NRC Comments NRC Comment:

(7) AP600 assumed single failure design flow of 25 SCFht per train will support only 5 people within the NICR envelope and remain within the OSIIA regulations of maintaining carbon dioxide levels at less than 0.5 percent. Ilowever, the current Westinghouse proposal is to permit up to 11 occupants into the main control room during a DBA. The staff has still not accepted the higher control room occupancy number which would result in carbon dioxide levels exceeding OSIIA regulations. In addition, it is unclear what control room occupancy number is assumed when performing heat load calculations in the main control room for post-72 hour actions.

Westinghouse Response:

A review of the literature beyond that presently referenced in SSAR section 6.4.8 has been completed with respect to providing supporting documentation for human tolerance of CO2 concentrations above the limit of 0.5%, established in Reference 1.

Reference 2 documents a Navy medical study performed on 23 volunteers exposed for 42 continuous days to a 1.5% CO, concentration. The study evaluated basal pulse rate, blood pressure, oral temperatures, I weight, and the respiratory response to various degrees of work loads. Reference 3 provides a more concise l summary of the results of that study (pp. 601) in that " .certain physiologic adaptations took place, and  ;

that mild evidence of stress reactions were apparent, There were, however, no alterations in the basic l physiologic functions or measurable decrement in psychomotor performance. These data were interpreted to j mean that' l.5% was the upper limit of tolerance for carbon dioxide during prolonged exposures." i Additional data is documented in Reference 4, which examined the effects of various elevated CO concentrations, with respect to potential equipment problems in spacecraft cabin atmospheres. The CO, concentrations studied were "0",8,15,21, and 30 mm Hg. The report summary notes that " .no difficulty was encountered by the exercising subjects at low CO levels of 8 and 15 mm Hg." [Aside: 0.03% CO, concentration correspond.s to ~ 0.23 mm Hg,8 mm Hg corresponds to ~ 1% concentration,15 mm Hg is -2%

concentration]

In considering the results of these studies as they pertain to the AP600, when a single failure is postulated for one train of compressed air delivered to the control room, in combination with a full complement of II individuals in the room, the CO2 level in the control room does not exceed I %. In light of the medical studies referenced below, it is safe to conclude that exposures to a level of 1 %, while above the Reference I criteria, is acceptable, especially when considering that they will not be continuously exposed to this level, nor will they be performing physically exerting activities.

In scenarios where the MCR doors are opened at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, the MCR CO2 content will become equivalent to outside air.

.. Heat loads from control room occupancy are discussed in the response to NRC Comment 9.

References

1. 29 CFR Part 1910 Subpart Z " Toxic and Hazardous Substances," and Part 1910.1000 Table Z-1,

" Limits for Air Contaminants."

268 SP

Attshment to NsD-NRC-97-5024 DCP!NRC0773 Docket No.: sTN-s2-003 Page 8 Westinghouse Responses to NRC Comments 1

2. V.F. Borum, et al, "The Effect of Exposure to Elevated Carbon Dioxide Tension over a Prolonged Period on Basal Physiological Functions and Cardiovascular Capacity," hiedical Research Laboratory Report No. 241, Bureau of hiedicine and Surgery, Navy Department Project Nh1002 015.10.05.

3. J.H. Ebersole, "The New Dimensions of Submarine Medicine," The New England Journal of hiedicine, Volume 262, No.12, pp. 599-610.

l 4. R.D. Sinclair, et al, " Carbon Dioxide Tolerance Levels for Space Cabins," Proceedings of the 5th Annual Conference on Atmospheric Contamination in Confined Spaces," Ah1RL-TR-69-130.

September 16-18,1969, pp. 53-66.

i l

NRC Comment:

(8) Westinghouse has not established the environmental qualification for main control room sealing materials.

Westinghouse Response:

As discussed in SSAR Section 6.4.2.4, the h1CR pressure boundary is designed for low leakage.

Penetration sealing materials are designed to withstand 1/4 inch water gauge pressure differential.

Penetration seals are a combination of materials, such as silicone foam, ceramic fiber, rubber boots, silicone elastomer and silicone caulk. The expected environment is mild, and the seals are compatible with the materials of penetration commodities.

The pressure integrity of the h1CR pressure boundary will be tested at regular intervals per AP600 Technical Specification. Any damaged seals or leak path will be identified and repaired accordingly.

Steam from the SFP will not adversely impact the environment for the htCR sealing materials because the steam is vented from the fuel handling area directly to the atmosphere. This vent location is more than 150 feet from the A1CR. >

Environmental qualification of the htCR sealing materials beyond that of the supplier standard is not anticipated due to the mild environment.

NRC Comment:

(9) The methodology used to calculate the passive heat removal capability of the natural circulation ventilation of the main control room needs to be clarified.

Westinghouse Response:

As indicated in the response to NRC concern (b), Westinghouse has decided to add small ancillary fans to provide h1CR and I&C room ventilation in the post 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> period. This avoids complex analyses to determine natural ventilation, and these fans are small loads on the 15 kW ancillary diesels.

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. --. - . ~ ~ . - - - - =. - - - __. _ - _ .

Attachment to NSD-NRC-97-5024

, DCP!N RC0773 Docket No.: STN-52-003

. Page 4 Westinghouse Responses to NRC Comments To provide cooling and ventilation, the small ventilation ancillary fans maintain 6e htCR temperature close to the average outside air temperature. Heat loads from MCR occupancy up to 11 people and from the post accident monitoring equipment are accommodated. The ancillary fan inlet duct is connected to MCR HVAC main supply duct, upstream of the pressure boundary isolation dampers. The duct connection flange is accessible from the control room. SFP boiling does not affect the habitability of the MCR since its exhaust point is remote from the MCR intake.

NRC Comment:

(10) Westinghouse should address the habitability requirements of the technical support center (TSC) under accident and post-72 hour conditions.

Westinghouse Response:

Like the MCR, the TSC is located more than 150 feet from the steam venting location in the fuel handling area, so its habitability is not affected. Habitability of the TSC under accident conditions with offsite or onsite AC power available will be equivalent to the MCR as described in SSAR Section 9.4.1. In the accident and post 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> scenarios without offsite and onsite ac power sources, the TSC equipment would not be powered and ventilation is not available. MCR communication links with offsite locations would be used to support the MCR staff.

Civil Eneineerine and Geosciences Branch Comments NRC Comment:

In order to resolve the major seismic concerns discussed in the cover letter to this enclosure from the Civil Engineering and Geosciences Branch, Westinghouse should:

(11) Revise the seismic roof structure model to reflect the design changes of PCS tank structures and the increased amount of water.

Westinghouse Response:

The seismic model of the shield building roof is being updated to reflect the change in structure and water inventory. This model will also include snow mass as required by the NRC staff position. The analyses follow the same procedure used to develop the existing model which was reviewed by NRC staff during the meeting in June,1996. Mode shapes and frequencies are calculated from a 3D finite element model of the shield building roof and cylinder in which the water inventory is treated as rigid mass. A stick model is i I

developed having similar dynamic characteristics. The masses of this stick model are adjusted based on a separate sloshing analysis of the water in the tank. The following comparisons will be made between the existing stick model including sloshing mass, and the updated stick model including sloshing mass to l determine if the design changes are significant-  !

l

• frequency and mode shapes '

response spectrum analysis for seismic input at base of cylinder 2nl 9P

Attxhraent to NSD-NRC-97 5024 DCP/NRCo773 Docket No.: STN-37-o03 j Page 10 '

Westinghouse Responses to NRC Comments l The results cf the analyses will be evaluated to determine if the design changes are significant to global ,

behavior. Generally the change will be considered insignificant based on the following: I

• frequency of significant modes differ by less than 2% ,

translational acceleration response of structural masses in updated model do not exceed those from  !

the existing model by more than 5%

member forces at the base of the updated model do not exceed those from the existing model by more than 5% j

\

These comparisons will be completed and available for NRC review by April 15, 1997. If the comparisons j do not meet the acceptance criteria described above to demonstrate that the design changes are insignificant l to global behavior, the hard rock fixed base analysis of the nuclear island stick model will be repeated. I The masses of the nuclear island stick model will be increased to account for mass due to live load in l accordance with the staff position. Comparisons will be made at a few representative locations against the l tloor response spectra from the existing analyses at 5% damping. The change will be considered - .

insignificant based on the following: I frequency of significant peaks on the floor response spectra differ by less than 5% i magnitude of peaks of updated spectra does not exceed existing spectra by more than 10% l member forces from updated model do not exceed existing member forces by more than 10% i NRC Comment:

(12) Perform seismic analysis for each of the design site conditions and evaluate the impact (both global and local) of these design changes to the design of the PCS tank, shield building roof structures and nuclear island foundation mat, and in-structure response spectra which are to be used for the design of subsystems such as piping, l I

i Westinghouse Response:  !

The procedure to review impact of the design change is described in the response to NRC Comment 11. It is expected that this process will demonstrate that the design change has no significant global impact and that it is unnecessary to reanalyze each of the design site conditions.

The impact of the design change on the shield building roof will be included in an update of the local analyses and design calculations for the roof. These will follow the same methodology as the existing calculations which were compared against independent staff analyses. These calculations will incorporate resolution of the remaining open issues from the staff review. The update of the design calculations and drawings will be completed and available for NRC review by May 30, 1997.

>l 19

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Attachment to NsD-NRC-97-5024 DCP!NRC0773

, , Dodet No.: STN-52-003 Page 11  ;

Westinghouse Responses to NRC Comments NRC Comment:

(13) evaluate the adequacy of the 39 inches of free board distance above the water surface to ensure there will not be any water splashing to the bottom of the fire water tank, and Westinghouse Response:

The analyses of the models described in the response to NRC Comment !! will update the water sloshing analysis and demonstrate adequacy of the free board. These calculations will be completed and available for NRC review by April 15, 1997.

NRC Comment:

(14) complete the design details of the fire water tank and make the design calculations available for staff review.

Westinghouse Response:

Design criteria for the fire water tank and liner design will be added to the SSAR. Design details will be available for NRC review by April 15. 1997.

Miscellaneous Comments NRC Comment:

(15) Westinghouse should provide additional details on the availability controls that will be placed j on the COL applicant to ensure that the post-72 hour diesel generators will be functional when ,

needed. This should include how the quarterly testing requirements will be implemented and I a description of the testing specifics. Westinghouse should also clarify what the 10 year IST system testing program is and how it differs from the quarterly testing.

Westinghouse Response:

The PCS recirculation pumps. the ancillary diesel generators and the ancillary fans are RTNSS important equipment. The following availability control recommendations for the COL applicant will be added to those for other RTNSS important equipment identified in WCAP-13856. Revision 0.

1 Passise Containment Cooling Recirculation Pump Recommendations J Both passive containment cooling water storage tank recirculation pumps should be available during all Modes of plant operation in order to support long term post accident operation. These pumps provide makeup to the passive containment cooling water storage tank from temporary water supplies after the ,

initial safety-related passive system water supplies are depleted. They will not be required to operate for I several days following an accident. This water is used to provide passive containment cooling and spent fuel cooling. SSAR section 6.2.2 provides additional information.

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Attachment to NsD-NRC-97-5024

, DCP/N RC0773

, Docket No.: STN-52-003

, Page 12 Westinghouse Responses to NRC Comments Each pump will be operated to provide passive containment cooling water storage tank recirculation Cow. The test frequency should be at least once every quarter.

Each pump will be operated to transfer water from the post 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> grade level storage tank to the .

passive containment cooling water storage tank at the required long term flow rate. The test frequency should be at least orce every 10 years.

Planned maintenance requiring less than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to perform, may be performed during any Mode .

of plant operation. Planned maintenance requiring more than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> should be performed during Mode 6 when the reactor has been shutdown for more than 150 hours0.00174 days <br />0.0417 hours <br />2.480159e-4 weeks <br />5.7075e-5 months <br />.

Remedial Action:

If these pumps are not availc.ble as described'in the preceding recommendations, then senior plant management as determined by the COL applicant, should be notified within one day and the availability of both pumps restored within 14 days. Pump restoration may include the use of temporary pumps.

If remedial action is not completed as recommended, then plant records should document the justification for management actions. These remedial recommendations are intended to provide timely return to service of these pumps.

Ancillary. Diesel Generator Recommendations Both ancillary diesel generators should be available during all Modes of plant operation in order to support long term post accident operation. The di,esel generators provide electrical power for post-accident monitoring, control room lighting and ventilation I&C room ventilation, and passive containment cooling water storage tank makeup pump operation. They will not be required to operate for several days following an accident. SSAR section 8.3.1.1.3 provides additional information.

Each diesel generator will be started and operated for at least one hour connected to a test load that is representative of its total post accident load. The diesel generators do not need to be operated at the same time. The test frequency should be at least once every quarter.

Each diesel generator will be started and operated for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> while providing power to the regulating transformer and the passive containment cooling water storage tank makeup pump and ancillary fans that it will power in a long term post accident condition. Test loads will be applied to the output of the regulating transformers that represent the loads required for post-accident monitoring and control room lighting. Both diesel generators will be operated at the same time.

The test frequency should be at least once every 10 years.

The ancillary diesel generator fuel oil storage tank level should be inspected at least once every two weeks to determine that it contains the minimum amount of fuel required for 4 days of operation of both diesels.

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Attachment to NsD-NRC-97-s024

, DCP/NRC0773

, Docket No.: STN-52-003

, Page 13 Westinghouse Responses to NRC Comments Planned maintenance requiring less than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to perform, may be performed during any Mode of plant operation. Planned maintenance requiring more than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> should be performed during Mode 6 when the reactor has been shutdown for more than 150 hours0.00174 days <br />0.0417 hours <br />2.480159e-4 weeks <br />5.7075e-5 months <br />.

l Remedial Action ,

l If these diesel generators are not available as described in the preceding recommendations. then l

senior plant management as determined by the COL applicant, should be notified within one day and the availability of both diesel generators restored within 14 days. Diesel generator restoration may include the use of temporary diesel generators.

If remedial action is not completed as recommended, then plant records should document the justification for management actions. These remedial recommendations are intended to provide i timely return to service of these diesel generators. ,

Ancillary Control Room Fans Recommendation Both ancillary control room faris should be available during all Modes of plant operation in order to support long term post accident operation. These fans provide ventilation cooling of the main control room by blowing outside air into the room in case the normal HVAC is unavailable and the safety-related passive system compressed air supply has become depleted. They will not be required to operate for several days following an accident.

Each fan will be operated with a test frequency of at least once every quarter.

The fans will be aligned to the control room and each fan will be operated to blow air into the control room. Power to the fans will be provided by the ancillary diesels. The test frequency should be at least once every 10 years.

Planned maintenance requiring less than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to perform, may be performed during any Mode of plant operation. Planned maintenance requiring more than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> should be performed during Mode 6 when the reactor has been shutdown for more than 150 hours0.00174 days <br />0.0417 hours <br />2.480159e-4 weeks <br />5.7075e-5 months <br />.

Remedial' Action:

If these fans are not available as described in the preceding recommendations, then senior plant management as determined by the COL applicant, should be notified within one day and the availability of both fans restored within 14 days. Fan restoration may include the use of temporary fans.

If remedial action is not completed as recommended, then plant records should document the l justification for management actions, These remedial recommendations are intended to provide timely return to service of these fans.

411P

. Attachment to NsD-NRC-97-5024 DCP/N RC0773 Docket No.: STN-52-003 Page 14 Westinghouse Responses to NRC Comments Ancillary I&C Room Fans Recommendation An ancillary I&C room fan should be available for each of two I&C rooms during all Modes of plant operation in order to support long term post accident operation. These fans provide ventilation cooling of the I&C rooms by blowing outside air into the room in case the normal HVAC is unavailable and the safety-related passive heat sinks have become depleted. They will not be required to operate for several days following an accident.

Each fan will be operated with a test frequency of at least once every quarter.

Each fan will be aligned to its associated I&C room and will be operated to blow air into the I&C room. at the required long term flow rate. Power to the fans will be provided by the ancillary diesels. The test frequency should be at least once every 10 years.

Planned maintenance requiring less than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to perform, may be performed during any Mode of plant operation. Planned maintenance requiring more than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> should be performed during Mode 6 when the reactor has been shutdown for more than 150 hours0.00174 days <br />0.0417 hours <br />2.480159e-4 weeks <br />5.7075e-5 months <br />.

t Remedial Action:

If these fans are nc,t available as described in the preceding recommendations, then senior plant management as determined by the COL applicant, should be notified within one day and the availability of both fans restored within 14 days. Fan restoration may include the use of temporary fans.

• l If remedial action is not completed as recommended, then plant records should document the '

justification for management actions. These remedial recommendations are intended to provide timely return to service of these fans.

NRC Comment:

(16) The electrical connutions between the 15 Kw post-72 hour diesel generators and the 480 volt regulating transformers is being made into a permanent connection. How will the cable run be protected to GDC 2 requirements.

Westinghouse Response:

The electrical connections between the 15 kW ancillary diesel generators and the 480 V regulatmg l transformers are protected from natural phenomena to the same extent as the ancillary generators  ;

themselves. Specifically, the equipment is protected against earthquakes,145 mph winds, and floods.

I 411P

i

, Attachment to NSD-NRC-97-5024 DCPfNRC0773

+

Docket No.: STN 52-003 Page 15 Westinghouse Responses to NRC Comments NRC Comment:

(17) The staff notes that the I&C equipment is qualified to a worst case environmental temperature of 120'F for 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> based on information in SSAR Section 7.1.4.1.6 and WCAP-13382.

Westinghouse should confirm that the I&C temperature and humidity qualification is adequate under the proposed revisions to post-72 hour actions and design changes.

Westinghouse Response:

The environmental qualification requirements for AP600 equipment are listed in SSAR Section 3.11.1. The environmental requirements for post-72 hours as stated in SSAR Section 3.11.3, Table 3.11-1, and i

Appendix 3D will be reviewed and revised (in SSAR Revision 12) as necessary based on ventilation with  !

the ancillary fans and outside air after 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Since the MCR and I&C rooms will be maintained near the conditions of the average outside air temperature, qualification of the I&C equipment for long term exposure to these conditions is within the equipment capability.

1 2*11P

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. Attachment to NsD-NRC-97-5024 DCP/ N RC0773 Docket No.: STN-52-003 Page 16 Westinghouse Responses to NRC Comments NRC Comment:

(18) Westinghouse should confirm that the applicable IE safety related electrical systems within the auxiliary building are qualified to the steam and humidity enviromnental conditions that may result from boiling of the spent fuel pool or explain why this is not a concern.

Westinghouse Response:

Table 3.11-1 of the SSAR provides a list which identifies the IE electrical equipment in the fuel handling l

~ area exposed to the steam environment (Environment Zone 11) in the event of SFP boiling. Spent fuel pool level and temperature instruments are qualified for this enviionmental zone. No other Class IE electrical equipment would be exposed to the steam since the fuel area is vented directly to atmosphere.

i

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Attnchment to NSD-NRC-97-50J4 DCP!N RC0773 Docket No.: SIN-52-003 Page 17 Westinghouse Resportses to NRC Comments f f ii i I ' If- fi-ll -[_

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