ML17299A669

Responds to Request & Commitments Made During 851008 Meeting & in Re Auxiliary Pressurizer Spray Sys. Implementation of Listed Enhancements Scheduled for First Refueling Outage for Unit 1.Concurrence Requested by 851022

ML17299A669
Person / Time
Site:	Palo Verde
Issue date:	10/15/1985
From:	Van Brunt E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	Knighton G Office of Nuclear Reactor Regulation
References
ANPP-33713-WFQ, TAC-56648, NUDOCS 8510170107
Download: ML17299A669 (107)

Text

REGULATORi NFORMATION DISTRIBUTION S EM (RIDS)

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'- ill ACCESSION NBR 8510170107 DOC ~ DATE: 85/10/15 NOTARIZED: YES, DOCKET" 0 FAC.IL:PN 50-528 Palo Verde Nuclear-Stationi Unit 1~ Ar)zona Publi 05000528 STN-50-529 Palo Verde Nuclear Stationi Unit ?( Arizona Publi 05000529 STN<<50>>530 Palo Verde Nuclear Station~

Unit 3g Arizona Publi 05000530 AUTH,NAME AUTHOR AFFILIATION VAN BRUNTrE,E, Arizona Nuclear Power Project (formerly Arizona Public Serv RECIP ~ NAMEi RECIPIENT AFFILIATION KNIGHTON<G AN.

Office of Nuclear Reactor Regulationi Director;

SUBJECT:

Responds to request 8 commitments made during 851008 meeting 8 in 850918 ltr re auxiliary pressurizer spray sys, Implementation of listed enhancements scheduled for first'efueling outage for Unit 1,Concurrence requested by 851022',

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~(p Arizona Nuclear Power Pro)ect P.o. SOX 52034 ~ PHOENIX. ARIZONA85072-2034 ANPP-33713-WFQ/TFQ October 15, 1985 Director of Nuclear Reactor Regulation Attention: Mr. George W. Knighton, Project Director PWR Project Directorate 87 Division of Pressurized Water Reactor Licensing B U. S. Nuclear Regulatory Commission Washington, D.C. 20555

Subject:

Palo Verde Nuclear Generating Station (PVNGS) Units 1, 2 and 3 Docket Nos. STN-50-528 (License No. NPF-41)/529/530 Auxiliary Pressurizer Spray Design File: 85-056-026. G.l.01.10

Reference:

(A) Letter from E. E. Van Brunt, Jr.,

ANPP, to J.

B. Martin,

NRC, dated September 18, 1985 (ANPP-33487).

(B) NUREG-0852, "Safety Evaluation Report Related to the Final Design of the Standard Nuclear Steam Supply Reference

System, CESSAR System 80", Supplement 1, dated March 1983.

(C) NUREG-1044, "Evaluation of the Need for a Rapid Depressurization Capability for Combustion Engineering Plants", dated December 1984.

Dear Mr. Knighton:

In meetings on September 20, 1985 and October 8, 1985, between representatives from the NRC staff, ANPP and Combustion Engineering, we discussed several aspects of the PVNGS Auxiliary Pressurizer Spray System (APSS). The discussion included design

history, Steam Generator Tube Rupture (SGTR) accidents, the existing APSS design, and proposed APSS design modifications.

This letter is submitted in response to the request made by the staff and our commitments made during the October 8, 1985 meeting, and our commitments made in Reference (A). The design history included discussions of the licensing basis for the APSS. The licensing basis for the APSS is founded on Branch Technical Position (BTP) RSB 5-1 for a Class 2 Plant which allows a) dependence on manual actions inside containment after a SSE or single failure or b) remaining at hot standby until manual actions or repairs are complete, if such actions are found to be acceptable for the individual plant. The APSS was reviewed by the NRC staff against the BTP RSB 5-1 requirements for a Class 2 plant, and their approval is documented in Section 5.4.3 of Reference (B). p5 fpf7p 1p7, pppppp28 Ql esgPf 5 - epDR ADO'. 0 pDR

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i ~ j Mr. George W. Knighton Palo Verde Nuclear Generating Station Units 1, 2 and 3 Auxiliary Pressurizer Spray Design ANPP-33713 Page Two The PVNGS SGTR analysis, documented in the PVNGS PSAR Appendix 15A, includes APSS operation at 1015 seconds after a SGTR. This analysis was performed in response to a staff request to model actions required by the operating procedures, rather than to form a licensing basis for mitigation of a SGTR. The effect of the APSS in the analysis is to cause an increase in pressurizer, liquid level which (along with adequate heat removal and minimum subcooling) allows the high pressure safety injection (HPSI) flow to be throttled. This HPSI throttling accomplishes the final phase of plant depressurization to shutdown cooling initiating conditions. To demonstrate that operation of the APSS is not required at 1015

seconds, Attachment 1 provides a revised SGTR analysis which confirms that APSS is not needed in the first two hours to mitigate the consequences of the accident, relative to meeting the acceptance criteria of 10CPR100.

This revised SGTR analysis shows a deferred reliance on APSS which is consistent with other accident scenarios which assume a loss-of-offsite power. That is, after the plant has stabilized and the accident has been essentially mitigated, APSS is used to depressurize the Reactor Coolant System to allow entry into shutdown cooling as part of the post-accident recovery. The scope of the APSS was also discussed at the September 20, 1985 and October, 8, 1985 meetings. It is our position that the APSS portion of the CVCS includes two safety-related auxiliary spray valves in parallel (CH-203 and CH-205), a check valve (CH-431) and their associated piping. This is consistent with the NRC staff's description of the APSS portion of the CVCS as documented in Appendix B of Reference (C). The PVNGS depressurization capability includes the APSS and a source of borated water (via charging system). Attachment 2, provides a summary of the design features of each component in the primary path between the refueling water tank and the pressurizer. Attachment 2 also provides information concerning compensating operator actions for failure of a component. Any or all of these operator actions, if necessary, are reasonably achievable within the time period (2 hours) used in the SGTR reanalysis for commencement of operation of the APSS. The capabilities of the PVNGS design meet the requirements of BTP RSB 5-1, for a Class 2 plant, and are commensurate with the needs for depressurization. At the October 8, 1985 meeting, we also presented a description of our planned enhancements to the CVCS as a result of our evaluation of the September 12, 1985 Outage. These enhancements, which are further described in Attachment 3, will Provide power .to CH-501 and 536 from an IE Motor Control 'enter following a Loss-ofWffsite Power and/or a Safety Infection Actuation Signals

0 1'e H 1 P I'P ~ I 'Ti 'I 1 ) 'I

Mr. George W. Knighton Palo Verde Nuclear Generating Station Units 1, 2 and 3 Auxiliary Pressurizer Spray Design ANPP-33713 Page Three Enhance the reliability of the Volume Control Tank (VCT) level indication. Provide automatic realignment of CH-501 and 536 on Lo-Lo VCT level and loss' mffsite

power, to align charging pump suction from the refueling water tank.

The schedule for implementation for these enhancements is the first refueling outage for Unit 1, prior to exceeding 5X power for Unit 2, and prior to fuel load for Unit 3. The information and commitments provided by this letter should address the NRC staff's concerns on the APSS and charging capabilities, and we request your concurrence with the proposed modifications by October 22, 1985 so that committed schedules can be met. Please contact Mr. W. F. Quinn of my staff if you have any questions on this matter. Very truly yours, E. E. Van Brunt, Jr. Executive Vice President Project Director EEVB/TFQ/dim Attachments

1. Revised Steam Generator Tube Rupture Analysis 2.

PVNGS Auxiliary Pressurizer Spray and Charging Component Capability Summary

3. Engineering Evaluation of September 12, 1985 Outage cc:

R. P. Zimmerman E. A. Licitra A. C. Gehr M. Ley

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STATE OF ARIZONA ) ) ss. COUNTY OF MARICOPA) I, Edwin E. Van Brunt, Jr., represent that I am Executive Vice President, Arizona Nuclear Power Project, that the foregoing document has been signed by me on behalf of Arizona Public Service Company with full authority to do so, that I have read such document and know its contents, and that to the best of my knowledge and belief, the statements made therein are true. I Edwin E. Van Brunt, Jr. Sworn to before me this day 'o , 1985. Notary Public Hy: Commission Expires: My Commlsslon Expires April B, 1987

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ATTACHMENT 1 STEAM GENERATOR TUBE RUPTURE WITH A LOSS OF OFFSITE POWER AND A FULLY STUCK OPEN ATMOSPHERIC DUMP VALVE (ADV) f The Steam Generator Tube Rupture (SGTR) analysis currently'ontained in the PVNGS FSAR Appendix 15A, was performed.in response to a NRC staff concern that tl operator actions may affect the assumption of 'a worst "single failure. As a

result, the Appendix 15A analysis was submitted, (Appendix to Reference 1 and l

subsequent information in References' and 3) considering the operator actions 1 that are outlined in the plant procedures. These procedures provide guidance to the operator in the event of a SGTR with a Loss of Offsite Power to lower RCS pressure through the use of the Auxiliary Pressurizer Spray System (APSS).

Thus, the current Appendix 15A analysis assumes an operator action at 1015 seconds to initiate the APSS.

In response to a staff concern that this action was required to achieve acceptable consequences, the event has been reanalyzed without operator action to initiate the APSS until two hours after the event initiation. A two-hour time delay was chosen for two reasons.

First, this delay will maximize the two-hour Exclusion Area Boundary dose for this event.

Second, the two-hour delay provides adequate time to manually establish auxiliary pressurizer

spray, even in the event failures in the system occur per BTP 5-1.

IDENTIFICATION OF EVENT AND CAUSES This transient analysis is similar to that described in the PVNGS FSAR Appendix 15A except that initiation of auxiliary pressurizer spray occurs at two hours. It assumes that the plant is challenged by a steam generator tube rupture including the conservative assumptions of the Standard Review Plan Section 15.6.3 (1088 of offsite power, accident meteorology, iodine spiking, etc.). In addition, the analysis postulates that 1) the operators open an ADV on the affected steam generator and

2) it runs to the full open position and

3) it sticks open for the duration of the transient.

0306K/0014K

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SE UENCE OF EVENTS AND SYSTEMS OPERATION Refer to the PVNGS FSAR Appendix 15A for a description of the event assumptions. In addition, Table 1 of this Attachment 1 provides the sequence of events and setpoint values used for the revised steam generator tube rupture analysis. The sequence of events and setpoint values are identical to that described in the PVNGS FSAR Appendix 15A, through 1015 seconds at which time it was assumed the operator initiated auxiliary pressurizer spray. This reanalysis conservatively delays the initiation of auxiliary pressurizer spray until two hours into the event. By delaying auxiliary pressurizer spray to this time, the primary to secondary tube leak is maximized and therefore, the 0-2 hour exclusion area boundary (EAB) radiological consequences are maximized. Most of the dose occurs in the first two hours. At 8 hours, plant conditions are such that the operator initiates shutdown cooling system operation and the radioactive releases are terminated. Therefore, with a delay in initiating auxiliary pressurizer spray until 2 hours, the limiting 0-2 hour EAB radiological consequences of a SGTR will not be reduced by the depressurization caused by auxiliary pressurizer spray. The two-hour time delay for initiating auxiliary pressurizer spray provides the operator adequate time to manually establish auxiliary pressurizer

spray, even in the event of failures in the system per BTP 5-1.

Due to the increased primary to secondary leak rate, the steam generator tubes are covered at 1347 seconds which is slightly earlier than the PVNGS FSAR Appendix 15A analysis. Approximately 10 minutes after auxiliary pressurizer spray is initiated, pressurizer level is regained. The operator then controls high pressure safety infection flow, backup pressurizer heater

output, and auxiliary pressurizer spray flow to control RCS pressure and subcooling and conducts an orderly approach to shutdown cooling entrance conditions.

The dynamic behavior of important NSSS parameters following, this revised steam generator tube rupture analysis are provided in Figures 1-14 of this Attachment l. ANALYSIS OF EVENTS AND CONSE UENCES The mathematical model used for 'this analysis is described in CESSAR'ection 15D.3.1.A. A ~ I ~ II A wc y r>r M fly lk t J I I ~ 4 0

RADIOLOGICAL CONSE UENCES The physical model is the same as that discussed in CESSAR Section 15D.3.2 except that the ADV of the affected steam generator opens fully. In order to reduce the radiological releases, the operator takes appropriate actions to recover the U-tubes of the affected steam generator. Actions assumed in this analysis included overriding the automatic isolation of Auxiliary Feed Water (AFW) flow to the affected steam generator and diverting the flow of both AFW pumps to the affected steam generator. The mathematical dose model is as described in CESSAR Section 15D.3.2.C. The assumptions and conditions employed for the evaluation of radiological releases are the same as those discussed in CESSAR Section 15D.3'.B with the exceptions of assumptions 7, 9, and 10. The assumptions used in this analysis are: 70 During the period when the water level in the affected steam generator is above the top of the U-tubesp that portion of the leaking primary fluid which flashes to steam'pon entering the steam generator is assumed to be released to the atmosphere with a decontamination factor (DF) of 1.0 ~ The portion of the leaked fluid that does not flash, mixes with the liquid in the steam generator and is released to the atmosphere with a DF of 100. During that period when the water level is below the top of the U-tubes, it is assumed that all the leaking primary fluid escapes to the atmosphere with a DF of 1.0, which is more conservative than the CESSAR assumption. No credit is taken for the presence of steam separators and dryers which would retain a part of the escaping primary liquid in the steam generator. 9. The 0-2 hour and 2-8 hour primary-to-secondary leakage through the rupture are 447,600 ibm and 570,400 ibm, respectively. 10. The PVNGS site specific atmospheric dispersion factors employed in -4 3 the analyses are: 3.1 x 10 sec/m for the exclusion axea -5 3 boundary and 5.1 x 10 sec/m for the low population zone. ~ ~ 4 ) P r ~ 4 4 ~ 1 ~ 4 4 ~ 4 l I l 4 4 4 v V

I The two-hour exclusion area boundary (EAB) and the eight-hour low population zone (LPZ) boundary inhalation doses for both the Generated Iodine Spike (GIS) and the Preaccident Iodine Spike (PIS) are presented in Table 2 of, this. The calculated EAB and LPZ doses are well within the acceptance criteria of 10CFR Part 100. The dose results from the PVNGS FSAR Appendix 15A are also provided in Table 2 for reference. CONCLUSIONS Assuming the APSS is not actuated until two hours after the

event, the radiological releases calculated for the SGTR event with a loss of offsite power and a fully stuck open ADV are well within the acceptance criteria of 10CFR100.

The secondary system pressures are well below the llOX of the design pressure limits ensuring the integrity of these systems. The time assumed for operator action of the auxiliary spray system is consistent with the system design.

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REFERENCES (1) Letter from E. E. Van Brunt, Jr.,

APS, to G.

W.

Knighton, NRC, dated September 19,

1984, ANPP-30572.

Subject:

Steam Generator Tube Rupture Analysis. (2) Letter from E. E. Van Brunt, Jr., APS to G. W.

Knighton, NRC, dated October 5,

1984, ANPP-30746.

Subject:

Steam Generator Tube Rupture Analysis. I ( (3) Letter from E. E. Van Brunt, Jr.,

APS, to G.

W. Knighton,

NRC, dated October 24,

1984, ANPP-30938.

Subject:

Steam Generator Tube Rupture Analysis.

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TABLE 1 SE UENCE OF EVENTS FOR A STEAM GENERATOR TUBE RUPTURE WITH A LOSS OF OFFSITE POWER AND FULLY STUCK OPEN ADV (Sheet 1 of 3) (See) Event Setpoint* or Value Success Path or Comment 0.0 Tube Rupture Occurs 40 40 47 47.15 48 51 Third Charging Pump Started, feet below program level Letdown Control Valve Throttled Back to Minimum Flow, feet below program level CPC Hot Leg Saturation Trip Signal Generated Trip Breakers Open Turbine/Generator Trip Loss of Offsite Power -0.75 -0.75 Primary System Integrity Primary System Integrity Reactivity Control Reactivity Control Secondary System Integrity 52 52 121 LH Main Steam Safety Valves Open, psia RH Main Steam Safety Valves Open, psia Maximum Steam Generator Pressures Both Steam Generatorsy psia Steam Generator Water Level Reaches Auxiliary Feedwater Actuation Signal (AFAS) Analysis Setpoint in Unaffected Generator, percent wide range level 1265 1265 1330 25 Secondary System Integrity Secondary System Integrity Secondary System Integrity 122 AFAS Generated 131 Steam Generator Water level Reaches AFAS Analysis Setpoint in the Affected Generator, percent wide range level 25 Secondary System Integrity

TABLE 1 SE UENCE OF EVENTS FOR A STEAM GENERATOR TUBE RUPTURE WITH A LOSS OF OFFSITE POWER AND FULLY STUCK OPEN ADV (Sheet 2 of 3 (See) Event Setpoint* or Value Success Path or Comment 132 AFAS Generated 167.0 Auxiliary Feedwater Initiated to Unaffected Steam Generator Secondary System Integrity 177.0 Auxiliary Feedwater Initiated to Affected Steam Generator Secondary System Integrity 460 Operator Initiates Plant Cooldown by Opening One ADV on Each SG ADV of the Affected SG Instantaneously Opens Fully Reactor Heat Removal 484 Pressurizer Empties 513 MSIS Actuation, Secondary

Pressure, psia 535 Automated Isolation of AFW to Affected SG, AP SGs, psi 919 185 Secondary System Integrity Secondary System Integrity 581 Pressurizer Pressure Reaches Safety Injection Actuation Signal (SIAS) Analysis

Setpoint, psia 581 Safety Injection Actuation Signal Generated 581 Safety Injection Flow Initiated 1578 (1837)

Reactivity Control Reactivity Control 655 Operator Overrides the AFW Isolation Signal and Starts Feeding the Affected SG with 'FW 775 Operator Takes Manual Control of the AFW System, Feeds Affected SG with Both AFW Pumps

IL

a I 4 TABLE 1 SE UENCE OF EVENTS FOR A STEAM GENERATOR TUBE RUPTURE WITH A LOSS OF OFFSITE POWER AND FULLY STUCK OPEN ADV (Sheet 3 of 3 (Sec) Event Setpoint* or Value I Success Path or Comment 895 Operator Shuts the ADV of the Unaffected Steam Generator 1347 Level in the Affected SG Above the Top of U-tubes, percent wide range 71.5 7200 7800 7800 28j800 Operator Initiates Auxiliary Spray to the Pressurizer Pressurizer Level, percent Operator Controls HPSI Flow, Backup Pressurizer Heater

Output, and Auxiliary Spray Flow to Control RCS Pressure and Subcooling,

'F Shutdown Cooling Entry Conditions are Reached RCS psia/'F 50 20 400/350 28$ 800 Operator Activates Shutdown Cooling System

• Where the Technical Specification (TS) Setpoint is different from what was used, the TS value is listed in parenthesis for reference.

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TABLE 2 RADIOLOGICAL CONSE UENCES OF THE STEAM GENERTOR TUBE RUPTURE WITH A LOSS OF OFFSITE POWER AND FULLY STUCK OPEN ADV APSS OPERATION DELAYED TWO HOURS Offsite Doses Rems Location 1 ~ Exclusion Area Boundary 0-2 hr. Thyroid 2. Low Population Zone Outer Boundary 0-8 hr. Thyroid GIS 42 22 PIS 208 RADIOLOGICAL CONSE UENCES OF THE STEAM GENERTOR TUBE RUPTURE WITH A LOSS OF OFFSITE POWER AND FULLY STUCK OPEN ADV APSS OPERATION AT 1015 SECONDS (PVNGS FSAR APPENDIX 15A Offsite Doses Rems Location GIS PIS 1. Exclusion Area Boundary 0-2 hr. Thyroid 2. Low Population Zone Outer Boundary 0-8 hr. Thyroid 40 20 200 41

FIGURE 1 CORE POMER VS, TItlE (SHEET '1 OF 2) 100 80 60 CD CD (0 20 1200 2t'00 3600 4800

TINE, SECONDS 6000 7200

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FIGURE j. CORE POWER YS, TINE (SHEET 2 OF 2) 120 100 80 60 CD 00 20 5000 10000 15000 20000 25000

TINE, SECONDS SOCIO

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FIGURE 2 RCS PRESSURE VS. TINE CSHEET 1 OF 2) 2500 2000 li00 1000 500 1200 28400 3600

TINE, SECONDS

~800 6000 72CO

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FIGURE 2 RCS PRESSURE VS. TINE (SHEET 2 OF 2) OPERATOR TAKES CONTROL Of PLANT-OPENS ONE ADV IN EACH SG 2000 a-1500 a 1000 OPERATOR INITIATES AUXILIARYSPRAY OPERATOR CONTROLS AUXILIARYSPRAYFLOM, BACKUP PRESSURIZER HEATER OUTPUT, AND HPSI FLOH IN ORDER TO KEEP THE RCS 20 F SVBCOOLED 500 RCS REACHES SHUTDOHN COOLING ENTRY CONDITIONS 5300 10000 15000 20000 25000 3OCQL

TPE, SEC"NDS

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FIGURE 3 CORE COOLANT TB'IPERATURES VS, TIYiE (SHEET 1 OF 2) 650 575 ~HOT LEG 500 5 t425 AVERAGE CO CD 350 COLO LEO~ 275 200 1200 21400 3600. l"800 Tt'lE, SECONDS 7ZCO

I

FIGURE 3 CORE COOLANT TEIlPERATURE VS. TINE (SHEET 2 OF 2) CD 500 425 350 IJJ CAHOT LEG AYERAGE COLD LEG 275 200 0 5000 10000 15000 20000

TINE, SECONDS 25000 3CC":0

1

FI6URE 4 UPPER HEAD TE"tPERATURE VS TINE (SHEET 1 OF 2) 650 550 500 450 400 350 300 0 1200 24OO 3600

TITHE, SECONDS 4800 6000 72"0

FIGURE 0 UPPER HEAD TENPERATURE VS. TIt1E (SHEET 2 OF 2) 650 550 500 4J 450 000 350 300 0 5000 itj000 15000 Tli'lE, SECONOS 20000 25000 30iQO

t I f

0 FI6URE 5 PRESSURIZER I'JATER VOLU."lE VS. TIME (SHEET 1 OF 2) 2000 1500 1000 500 1200 2000 3600

TtNE, SECONDS 0800 6660 72GO

FIGURE 5 PRESSURIZER HATER VOLUl1E VS, TIVE (SHEET 2 OF 2) 2000 1500 OPERATOR CONTROLS AUXILIARYSPRAY, BACKUP PRESSURIZER

HEATERS, AND HPSI FLOE TO MAIi4TAIN 20~F SUBCOOLfi'tG 1000 500 OPERATOR INITIATES AUXILIARYSPRAY

-500 5000 10000 1)000 ?0000 25 CO 3OOOO Tli'lE, SECG ~ITS

f 1

FIGURE 6 LIQUID LEYEL MOYE. 73P OF HOT LEGS (SHEET 1 OF 2) 2000 TOP OF RV~ 1600 1200 CD 800 L4 000 TOP OF HOT LEG 00 ]200 2000 3600 4800 6000 7200 TIiIE, SECONDS

FIGURE 6 LIQUID LEVEL AB3VE 10P OF HOT LEGS (SHEET 2 OF 2) 2000 TOP CF RV 2.600 1200 CD 800 CD UJ 000 (WATER LEVEL RENAlNS AT TOP OF HOT LEGS) 0 0 TOP OF HOT LEGS 5000 10000 15000 20000 25000 >OOOO

TINE, SECONDS

FI6URE 7 RCS LIQUID NASS VS TINE (SHEET 1 OF 2) 6no 550 5nn 450 0 1200 2400 5600 480Ij 6000 7200 TI~E, SECONDS

FIGURE 7 RCS LIQUID NASS YS. TINE (SHEET 2 OF 2) 700 650 600 CD 550 5 500 450 40() 5000 10000 15000 20000 TIME, SECONDS

FIGURE 8 STEAN GENERATOR PRESSURE VS, TINE (SHEET 1 OF 2) 1400 1000 800 600 5 400 200 1200 2400 3600 4800 6000

TtME, SECONDS 7200

I I

FIGURE 8 STEAN GENERATOR PRESSURE VS. TINE (SHEET 2 OF 2) 1~<00 j.::OO c F000 800 600 000 HSIYS CLOSE UNAFFECTED SG 200 AFFECTED SG 5000 ]OPPP 15000 20000 TIr~E, SECONDS 25000 30000

t

FIGURE 9 INTEGRATED AFW FLOW TO AFFECTED SG VS, TINE (SHEET 1 OF 2) 1200 " 1000 800 CD 600 c5 qpp 200 1200 2400 3t".00 TIME, SECONDS 6000

tl Iii

FIGURE 9 INTEGRATED AFM FLOW TO AFFECTED SG yS, TPE-(SHEET 2 0F 2) 1000 800 600 ch 5 000 200 0 0 5000 100GO 15000 20000

TINE, SECONDS 25000 3C~"< 3

FI6URE 10 TUBE LEAK RATE VS, TIt'lE (SHEET 1 OF 2) 70 50 00 50 20 10 1200 2000 5600

TtjRE, SECONDS 0800 6000 7200

I I

FI6URE 10 TUBE LEAK RATE VS TI,tE (SHEET 2 OF 2)

7G AUXI LIARY SPRAY INITIATED 50 40 30 OPERATOR OPENS ADV 20 5000 10000 15000

20000 25000 30000 Tli'lE, SECONDS

FIGURE 11 INTEGRATED LEAK FLOtI VS. TINE (SHEET 1 OF 2) 1200 1000 c) 800 600 400 200 1200 2400 3600 4800 Tlf'1E, SECONDS 6000 72"0

FIGURE 11 INTEGRATED LEAK FLOI'! VS, TINE (SHEET 2 OF 2) 1200 800 600 000 200 5000 10000 15000 20000 TIi"E, SECONDS 25000 30000

FIGURE 12 FRACTION'OF LEAK FLASHED VS, TINE (SHEET 1 OF 2) 1.0 0,16-Ch 0,12 CD 0,08 0,04 0,00 0 1200 2400 3600 TlflE, SECGiIDS -'.<00

FI6URE 12 FRACTION OF LEAK FLASHED VS, TINE (SHEET 2 OF 2) (AFFECTED STEA,'tI GENE'ATOR LEVEL ABOVE TOP OF U-TUBES) 5000 10000 15000 TIi'lE, SECONDS 20000 '5000 3cc 0

l' 1 II

FIGURE 13 STEN GENERATOR ttASS VS, TIf'1E (SHEET I OF 2) 390 240 tnC) V 180 120 AFFECTED SG 60 UNAFFECTED SG 1200 2400 3600

TtME, SECONDS 4800 6000 7200

FIGORE 13 STEAM GENERATOR MASS YS, TIME (SHEET 2 OF 2) 360 200 AFFECTED SG~ 180 120 UNAFFECTED SG (OPERATOR FEEDS AFFECTED SG KITH BOTH AF}0 PUMPS) 5000 10000 1SOOO 20000 TIi'lE, SECONDS 25900

l l I h Il' I I

FIGURE 14 INTEGRATED ADV FLOW VS.. TI IE (SHEET 1 QF 2) 15GO 1200 900 600 300 1200 2400 3600 4800

TlHE, SECONDS 6000 7200

Ir I t f

FIGURE 10 INTEGRATED ADV FLOW VS, TIME (SHEET 2 OF 2) 1800 1500 CD 1200 900 600 I 500 5000 10000 aSO00

TIVE, SECONDS

~'F00 25000

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ATTACHMENT 2(a) PVNGS AUXILIARYPRESSURIZER SPRAY AND CHARGING COMPONENT CAPABILITY

SUMMARY

COMPONENT HV-532 I Pneumatic IValve I(Normally Iopen (NO) IFail Open) IRWT Isolation DESCRIPTION FUNCTION (b) ACTIVE/ PASSIVE ACTUATION SIGNAL IHand Swi Passive tch in IControl Room I(CR) SINGLE RECEIVES FAILURE ELECTRICAL POWER. E (c)I VULNERABILITY SINGLE FAILURE LOCATION OF (d) COMPENSATORY ACTIONI OPERATOR ACTION Non-IE alternate gravity feed path,(via CH-327,755,756, 757) Building No IOperator Error li) Operator Action Ii) Control Room to Reopen CH-532,I I or I Iii) Alignment of an lii) Auxiliary IMotor I RWT Gravity IFeed IOperate IValve (MOV) HV-536 d Active IHand Switch in ICR or Lo-Lo VCT IZ vel(g) IE(f) No IFails to Open li) Open CH-536 Ii) Auxiliary Ifrom CR manually, or I Building Iii) Establish alter-Iii) Auxiliary I I UV-501(e) MOV VCT Outlet Valve Active I Hand Switch in CR or Lo-Lo VCT Level IE(f) No I Fails to Close I from CR nate gravity feed suction by: a) Opening CH-327 and CH-757 for Charging Pump E, or b) Opening CH-327 and CH-756 for Charging Pump B, or c) Opening CH-327 and CH-755 for Charging Pump A Building i) Close CH-501 Ii) Auxiliary manually and Vent Building VCT, if necessary or 0308K/0014K

M YR I .I It lM R ~ '

ATTACHMENT 2(a) (Sheet 2 of 4) COMPONENT DESCRIPTION FUNCTION h ACTIVE/ PASSIVE ACTUATION SIGNAL RECEIVES ELECTRICAL POWER SINGLE FAILURE SINGLE FAILURE LOCATION OF (e) E (c)) VULNERABILITY COMPENSATORY ACTIONI OPEHATOR ACTION ii Close CH-322 ii Auxiliary

manually, open Building CH-327 and CH-757 manually and vent suctionl line, if neces sary, for estab-I lishing alter-nate gravity feed suction to I

charging pump E ) I iii) Close CH-319 liii)Auxiliary

manually, open Building CH-327 and CH-756 manuallyl and vent suction line, if necessary, for establish-ing alternate gravity feed-suction to charging pump Bl iv) Close CH-316 liv) Auxiliary

manually, open Building CH-327 and CH-755 manually and vent suctionl line, if neces-I sary, for estab-I lishing alter-nate gravity feed suction to charging pump A CHA-P01

)Reciprocating I CHB-POl IPumps CHE-P01 Charging Pumps I Active IHand Switch in ICR. or )Pressurizer )Level I IE Yes Fails to Start IStart Pump B or E Fails to Start (Start Pump A or E Fails to Start IStart Pump A or B I I )Control Room IControl Room IControl Room I I

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ATTACHMENT 2(a) (Sheet 3 of 4) COMPONENT DESCRIPTION 'FUNCTION b ACTIVE/ PASSIVE ACTUATION SIGNAL RECEIVES ELECTRICAL POWER SINGLE FAILURE E (c)I VULNERABILITY SINGLE FAILURE LOCATION OF (d) COMPENSATORY ACTIONI OPERATOR ACTION LT-227 LT-226 LS-227 FT-212* PT-212 HV-524 HV-203 HV-205 PDV-240 HV-239 ILevel ITransmitter I ILevel ITransmitter I ILevel Switch I Flow ITransmitter I IPressure ITransmitter MOV l(N.O.-Fa'il-IAs-Is) I I ISolenoid IValve I ISolenoid IValve I I Pneumatic IValve (Fail IClose) I I Pneumatic IValve I(Fail Close) IVCT Level I I IVCT Level I I IProvides Isignal to BAM I Pumps, CH-501 ICH-514 and ICH-536 on Lo-ILo VCT level I Icharging Flow I Charging IPressure I IContainment IIsolation IA~iliary ISpray Valve I'Auxiliary ISpray Valve I I Charging IControl I ICharging Loop IIsolation I(Redundant to IPDV-240) I Passive N/A Passive N/A Passive N/A Passive N/A Passive IHand Switch in IcR Active Active Active Active IHand Switch in ICR I IHand Switch in ICR I IHand Switch in ICR or Charging I Line delta-P I IHand Switch in CR Active ILo-Lo VCT level IE(h) IE(h) IE(h) IE IE IE IE IE Non-IE Non-IE No No No Yes Yes Yes Yes Yes No No IInaccurate IIndication I-IInaccurate IIndication IIFail to Switch Icomparator(i) IAlarm in CR IIcomparator(i) IAlarm in CR I IOperator Action to I Iclose CH-501 and IOpen CH-536 N/A N/A Control Room IInaccurate I Indication I IInaccurate IIndication I PT-212 FT-212 IFails to Open IOpen HV-203 I I IFails to Close Iclose HV-239 N/A N/A li) Control Room Ilii) Auxiliary Building IControl Room I I IControl Room I I I control Room IFails to Close IClose PDV-240 IControl Room IOperator li) Operator Action IError I in CR, or lii) Manual Opening I of CH-524 I IFails to Open IOpen HV-205

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ATTACHMENT 2(a) (Sheet 4 of 4) NOTES: (a) The modifications discussed in Attachment 3 are reflected in this Attachment. 1 (b) An active component is defined as a component which is required to function for operation of the auxiliary pressurizer spray or charging capability. A passive component is defined as a component which is not required to function for operation of the auxiliary pressurizer spray or charging portions of the CVCS, however, the component may provide the operator with system performance indication. Therefore, the failure of these components were considered in this =review. (c) Environmental Qualification (EQ) per requirements of 10CFR50.49. (d) CH-327 Auxiliary Building, Elevation 74'H-755,

756, 757 Auxiliary Building, Elevation 100'H-501 Auxiliary Building, Elevation 100'H-316,

319, 322 Auxiliary Building, Elevation 100'H-524, Auxiliary Building, Elevation 88'e).

NRC Memorandum dated October 6, 1981, "Summary of September 17, 1981 Meeting Regarding CE Appeal of Staff Positions", Item 5, states that the staff required CH-141 (now CH-536) and CH-501 to be operable from the control room, but accepted control-grade operators for these valves provided power is supplied from a vital bus. (f) Design change willprovide power to valves HV-536 and UV-501 from a IE Motor Control Center (MCC). This MCC remains powered on a SIAS and is resequenced on a loss of offsite power. (g) Design change to implement automatic opening of HV-536 on Lo-Lo VCT level and a loss of offsite power. (h) Transmitters are automatically switched to a IE power source on LOP. (i) Design change to implement separate wet/dry reference legs for VCT level transmitters, and to provide a comparator alarm, in the control room, to indicate a difference in indication between transmitters LT-226 and LT-227.

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ATTACHMENT 3 RESULTS OF ENGINEERING EVALUATION OF SEPTEMBER 12 EVENT EVALUATION In response to the Unit 1 outage on September 12

1985, ANPP conducted an engineering evaluation of the design and operation of the PVNGS charging and auxiliary pressurizer spray systems (APSS).

The objectives of the evaluation were to 1) review and verify conformance to the licensing basis for the

system, 2) compare the perf ormance of the system during the September 12 outage against its design function,

3) examine the system for vulnerabilities and

4) determine the ability of operator action required to compensate for system and component malfunctions.

The evaluation consisted of a coordinated multi-disciplined review by

ANPP, Combustion Engineering and Bechtel engineering and the ANPP Operations Department.

It included a detailed review of the

system, identifying each component according to its safety classification and function during auxiliary spray and charging system operation, and a single failure analysis.

Attachment 2 summarizes the system, its component functions, and the operator actions required to accommodate active component failures. The evaluation of the design and operation of the APSS determined the system, as designed, to'e in accordance with the licensing basis for this system. Recognizing that operator action outside the control room may be required to accommodate single active failures, it is concluded that all presently postulated operator actions are acceptable and, consistent with BTP RSB 5-1 Cla'ss 2 plants. No mechanical or piping enhancements, such as additional redundant valves or flow paths, are necessary to meet the licensing basis for PVNGS ~

However, our evaluation determined a

system enhancement could be made to prevent a failure to isolate the Volume Control Tank (CH-501 fails to close) upon loss of liquid inventory, resulting in introduction of the VCT hydrogen cover gas into the charging pump suction piping. If this condition were to occur during a loss of off-site

power, the reasonable operator action to

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recover from this condition would require closing the manual isolation valves on the individual charging pump suction lines (see Figure 1 of this Attachment

3) thereby isolating the VCT from the charging

pumps, venting off the short section of piping between the isolation valves and the charging

pumps, and aligning an alternate gravity feed line from the Refueling Water Tank (RWT) by opening manual valves CH-327 and CH-755 through

-757. This action can be taken and the system restored to operable status within the two hour time requirement established in the revised Steam Generator Tube Rupture analysis. However, to minimize operator actions, enhancements in the reliability of the Volume Control Tank (VCT) level instrumentation, the power supply to valves CH-501 (VCT outlet valve) and CH-536 (RWT gravity feed line), and in the provision for automatic realignment of the charging pumps to alternate suction sources will be made to reduce the potential for gas binding the charging

pumps, provide a

large reduction in the potential for loss of auxiliary pressurizer spray and charging capability and result in system capabilities commensurate with the system usage. DESIGN MODIFICATIONS OBJECTIVES The objectives of the three modifications to the Palo Verde design that will be implemented are to: 1. Improve the operator's ability to operate the charging/auxiliary spray system from the control room, 2. Provide an automatic function to reduce the amount of required operator action, and 3. Improve the reliability of control grade level instrumentation on the Volume Control Tank. DESIGN MODIFICATIONS Provide ower to Valves CH-501 and CH-536 From an IE MCC The existing PVNGS design is such that the non-IE Motor Control Center (MCC) associated with valves CH-501 and CH-536 is automatically shed on a Safety Injection Actuation Signal (SIAS). The power supply to

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these valves will be modified to provide power from Class IE Motor Control Center (MCC) M-35. The cable used to connect these valves to the Class IE MCC does not meet Class IE standards, therefore, an appropriate isolation device consisting of two Class IE breakers in series will be provided to meet the requirements of IEEE 279 (see Figure 3). The MCC M-35 that will supply valves CH-501 and CH-536 is not automatically shed from the Class IE bus on a Safety Infection Actuation Signal (SIAS) and is automatically sequenced on to the Emergency Train A Bus following a Loss of Off-site Power (LOP). Therefore, this design change accomplishes design objective number l. Enhanced Automatic Reali ment to the RWT To eliminate the need for the operator to manually align the suction of the charging pumps to the RWT, the existing automatic transfer on lo-lo VCT level indication feature will be enhanced. With the existing

design, a lo-lo VCT level indication causes the automatic realignment of the charging pumps to the Boric Acid Make-up Pump flow path by opening valve CH-514 and closing valve CH-501.

A design modification will be implemented to allow automatic realignment to the RWT gravity feed line via valve CH-536 on lo-lo VCT level when the non-class IE powered Boric Acid Make-up Pump flow path is unavailable due to loss of off-site power. This will be accomplished by instrumentation sensing a loss of power to valve CH-514 and causing valve CH-536 to open then on lo-lo VCT level signal.

Thus, alignment of the charging pumps will be selectively made to either of two flow paths from the RWT depending on whether off-site power is available.

This modification will accomplish design objective number 2. Enhanced VCT Level Instrumentation The VCT level monitoring system will be modified to significantly reduce the potential for malfunction (with subsequent loss of automatic control functions) or incorrect operator action based on erroneous level indication.

The incorrect level in the common reference leg to LT-226 and LT-227 in the existing design that caused the erroneous level indication during the September 12 event was caused by a'artially drained reference leg. The modification will be to install separate reference

legs, one wet and one

dry, to each of two (existing) level transmitters, LT-226 and LT-227 (see Figure 4).

This diverse redundancy minimizes the potential for incorrect level indication by eliminating the potential for a partially drained wet reference leg going undetected. A signal comparator will be added to alarm in the control room on the transmitters indicating a level difference. This alarm will alert the operator to possible incorrect indication or malfunction of either transmitter. This modification will accomplish design obgective number 3. gUHNARY With these three modifications, the operability of the charging and anxiliary spray systems is significantly enhanced and the potential for loss of system function is significantly reduced. In the unlikely event that system function is temporarily lost due to active component

failures, acceptable operator action in accordance with BTP RSB 5-1 for a Class 2 plant will restore the system to operable status.

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S IMPLIFIED SCHEMATIC OF PALO YERD CYCS SHOHIHG AUXILIARY SPRAY PORTION AND SOURCES OF BORATED HATER fAQI I&(IC hCIO Ir(tc((l(4 IN(K (Ef((EE I(I MIER IN(K (( CH.5)0 IATRIC hCIO Eh IC( II(4 EDUC IOR fACtl REhCECR INI(EUP &TER FVP 3 (3(R IC hC IO MKE(P QM I PBIC hCIV t~xpr CH ZICX CH ZIOY CH-5lt fRQl ILAIFI Chil OH lett ear(trms CH 5I 2 CH-521 LT-226f ZZ7 WLU(C CO(tleX. ZNIK CH-151 nl-156 CII- .155 CIA'il(4 Rf4' GWNII4 RJP Z R-ZIZ l( 2(Z-5EE ((Eg ( PARE Ct( )Z1 CHN(0ltr. fIIP I to (Cr SEh( ((LIKI IC(( i(hl Q(.(rat gR FIGURE 1

SIMPLIFIED SCHEHATIC OF PA 0 D CVCS SHOHIHG AUXILIARY PORTIOH AHD SOURCES OF BOR'ATED MATER ALIXILIPRYSPRAY ~ KIITICrr OF CVCS FROrr LAST PA(:E ol-52'~r FI9r TO CVCS RMHER-ATIVE IAT IWrS 'I I I ~ I I L T 229 crr-2b) OI-2 5 J crr-25 crr-2(0 . FRCN RCS trAIN SPRAY VALVES I LE TECH FLOr F~ RCS FIGURE 2

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VALVE POWER SUPPLY CHANGE, F EXISTING MODIFIED IE BUS IE BUS T.RIP ON SIAS NON IE MCC IE MCC 50I 536 50l 556 CHANGE ENSURES OPERABILTY FROM CONTROL ROOM AFTER SIAS AND LOP SUCH THAT SUCTION COULD ~ BE ALIGNED TO RWT FROM VCT. FIGURE 3

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VOLUME. CONTROL TANK LEVEL lllCATION EXISTING MODIFIED VOLUME CONTROL TANK LT- -226 VOLUME CONTROL CONTROL ROOM TANK INDICATOR I I LT-227 LT-22 CONTROL (ROOM INDICATOR LT-227 IMP RC'/EME N TS LOW-I 'LEVEL SIGNAL AND CONTROL ROOM ALARM LOW LEVEL SIGNAL AND CONTROL ROOM ALARM SIGNAL COMPARATOR LALARM ON INDIGATED LEVEL DIFFERENCE I. SEPERATE REFERENCE LEG TO EACH TRANSMITTER ~ 2. ONE WET AND ONE DRY LEG TO PROVIDE DIVERSE REFERENCE

3. COMPARATOR ALARM PROVIDES INDICATION OF POSSIBLE LOSS OF CORRECT REFERENCE TO ONE OF THE TRANSMITTERS FIGURE 4

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