Evaluation of Pressure-Temperature Limits for Normal RPV ... · Startup LTOP event during normal plant startup.-IN 82-17, June 11, 1982 - Event occurred during startup after a refueling

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Evaluation of Pressure-Temperature Limits forNormal RPV Startup and Shutdown

Ron Gamble

NRC Public Meeting, Rockville MDAugust 28, 2012

Conclusions

" Review of several plant operating pressure and temperaturetime histories indicate that startup and shutdown sequences donot coincide with the ASME XI Appendix G pressure-temperature (P/T) limit curves.

" Protective devices provide additional assurance that normaloperation does not occur on or near the Appendix G P/T limits.

" The through-wall cracking frequency (TWCF) for low-temperature overpressure (LTOP) event pressures up to theAppendix G limits for normal reactor startup and shutdown areless than 1 E-7 per operating year.

" The conventional and risk-informed (RI)-Appendix G allowableP/T limits provide adequate margins against RPV failure for therange of postulated flaws important to reactor safety, including0.03t surface breaking flaws.

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ASME Section XI, Appendix G PIT Limits

" Relationship between P/T Limits and P/T OperatingConditions

- The operational pressure and the Appendix G allowable pressurelimits coincide, e.g., BWR pressure test.

- The operational pressure is lower than Appendix G allowablepressure, e.g, normal plant startup and shutdown.

" Events such as normal startup and shutdown proceedaccording to procedure and some abnormal occurrence(operator error or equipment malfunction) is required toreach the Appendix G P/T limits.

" In this instance, the Appendix G P/T limits are avoidancelimits, and the frequency with which the Appendix G P/Tlimits are reached is much less than 1.

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PWR Events

" Service experience indicates that the only major challengeto PWR Appendix G P/T limits is from overpressure eventsat low temperature (LTOP) where the system pressureexceeds the pressure conditions associated with normalplant startup and shutdown.

" Experience shows that LTOP events almost always occurduring reactor startup. The temperature range where theseevents occur is between 100 and 2001F.

" The current frequency for LTOP events has been estimatedas 10-2/operating year. (resolution of Generic Safety Issue94: NUREG-0933,)

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Example Assessments of PWR Normal Operating andLTOP Events

Startup- Definition of a representative PWR normal startup sequence (i.e.,

heatup [H/U])- Deterministic and probabilistic analyses of a representative normal

PWR startup sequence

- Deterministic and probabilistic analyses of a previous LTOP eventduring startup

• Shutdown- Definition of a representative PWR normal shutdown sequence

(i.e., cooldown transient [C/D])

- Deterministic and probabilistic analyses of a representative PWRshutdown sequence

- Deterministic and probabilistic analyses of a postulated LTOPevent during shutdown

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Example Assessments of PWR Normal Operating andLTOP Events

" Fluence at limiting axial weld = 4.83E19 n/cm 2 (60 EFPY)

" Cu = 0.213, Ni = 1.110, P = 0.19, Mn = 1.32 wt%

" Initial RTNDT = -560F" RTNDT at CBMI at 60 EFPY = 2660F" Analysis includes weld residual stress

" Cladding stress free temperature = 4880 F

" Cladding thickness = 0.25-inch

" Through clad circumferential flaw with total depth equal 0.2625-inch

* Total wall thickness (including cladding) = 8.75-inch

* Vessel inside radius = 86-inch

* Analyses performed with FAVOR 09.1 (includes weld residual stress)

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©2. . . . . . . . . . . . . . . . . . . ..

2. .. . . . . . . . .

Representative PWR Plant Startup Sequence

700

600

500

2.5

2.0

1.5

1.0 C

0.5

U-0

C)a.

E0

400

300

200

100

00 200

I 0.0

400 600 800 1000 1200 1400 1600 1800 2000

Time, minutes

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© 2012 Electric Power Research Institute, Inc. All rights reserved.

P/T Curves for Normal Startup, Appendix GLimits and Operational Constraints

2.5

2.0

U)

U)U/)

U.

Z~

1.5

1.0

0.5

0.00 100 200 300 400 500

Coolant Temperature, OF

600


0 2012 Electric Power Research Institute, Inc. All rights reserved. 8

Evaluation of Representative PWR Plant StartupSequence

40

35

30

25

20

15

10

-FAVOR Total KI

- - FAVOR Probabilistic Kmin

II

I

ICPI = 1.3E-7

CPF = 0TWCF = 0 LI 11111

E(U0~

U)

0C

0001~

4.i

0)

- d- - r- - - 7--- -

1OF/hr HU from 80F to 160F, then 23F/hr HU to 183F, then hold at 183F ___

for 10.5 hours, then HU at 33F/hr to 330F, then hold at 330 for 2.3 hours,then HU at 33F/hr to 550F

3% t = 0.2625" circumferential surface flawCladding t = 0.25"Aspect ratio = 6

5

00 200 400 600 800 1000 1200 1400 1600 1800 2000

Time, minutes

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Example Assessment of a PWR LTOP Event DuringStartup

LTOP event during normal plant startup.- IN 82-17, June 11, 1982

- Event occurred during startup after a refueling outage

- The reactor was shutdown and the RCS was water solid

- Event initiated at 11 0°F following start of the RC pumps, thepressure exceeded the normal operating pressure in the lowtemperature region (310 psi), the overpressure mitigation systemfailed to operate, the Appendix G pressure limit of 480 psi wasexceeded, and the pressure reached 750 psi before operator actionterminated the event.

- This illustration will assume the pressure reached the RI-Appendix Glimit of 1,214 psi. before the event was terminated.

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P/T Curves for Normal Startup, Appendix GLimits, Operational Constraints and LTOP Event

2.5

2.0

1.5

1.0

-RI Appendix G Limits: 10, 23 & 33 °F/hr

LTOP Set-Points

- -LTOP Enable Temperature

- Startup Curve

- Pump Curve

-June 1982 LTOP Event

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r- i /I

III

00(

Z/00000.5

0.0 '0

- +ff 0 -i5------ I 0

- * II

*IU * ___________________

1. III00

2200 300


400 500 600

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© 2012 Electric Power Research Institute, Inc. All rights reserved. 11

Evaluation of PWR Plant Startup with PressureTransient

40

35

30

25

20

15

10

E(U0~

(I)

a)

U)U)a)1~

*6.~Co

-FAVOR Total KI


CPI = 1.9E-6CPF = 5.4E-7

TWCF = <1E-8

1OF/hr HU from 80F to 160F, pressure transient to 1.214 ksi at 11OF, thenCD from 11OF to 8OF at 1OF/hr

3% t - 0.2625" circumferential surface flawCladding t = 0.25"Aspect ratio = 6

5

00 100 200 300 400 500

Time, minutes600 700 800 900 1000



Representative PWR Plant Shutdown Sequence

700 2.5

600

500 I75F/hr CD from 550F to 250F, then 46F/hr CD to175F, then hold at 175F for 12 hours, then CD at26F/hr to 120F, then CD at 6.8F/hr to 80F

2.0

NL-0

CL

E12

400

300

200

100

0

-Temperature

Pressure

--- mo

1.5

a

1.0 0

0.5

0.0

0 200 400 600 800 1000 1200Time, minutes

1400 1600 1800 2000

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P/T Curves for Normal Shutdown, Appendix GLimits and Operational Constraints

2.5

2.0

1.5

aS

Co

1.0

0.5

0.00 100 200 300 400 500


600

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Evaluation of Representative PWR PlantShutdown Sequence

40

35

30

25

20

15

10

E

0.

0/

I- FAVOR Total KI


CPI = 5E-10CPF = 0

TWCF = 0

75F/hr CD from 550F to 250F, then 46F/hr CD to 175F, then hold at 175Ffor 12 hours, then CD at 26F/hr to 120F, then CD at 6.8F/hr to 80F

3% t = 0.2625" circumferential surface flawCladding t = 0.25"Aspect ratio = 6

5

00 200 400 600 800 1000

Time, minutes1200 1400 1600 1800 2000

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Example Assessment of a Postulated PWR LTOPEvent During Shutdown

LTOP event during normal plant shutdown.- Although LTOP events typically don't occur during shutdown an

example is provided for illustration purposes.

- The LTOP event is postulated to occur at 1000 F, which correspondsto the temperature at which the system is near the end of coldshutdown, and the Appendix G allowable pressure is 1,170 psi.

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P/T Curves for Normal Shutdown, Appendix GLimits, Operational Constraints and LTOP Event

2.5

2.0

1.5

•RI-App G Allowable Pressure: 75, 46, 26 & 6.8 F/hr

LTOP Set-Points

- -LTOP Enable Temperature

- PWR Shutdown Curve

-Pump Curve

- Postulated LTOP Event

I

II

r_

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a- A1~, /1.0 A

__Oý iI / /V

0.5

0.0

ISI

I /07o-F _ a~

0

i II

4 t "I.

100 200 300Coolant Temperature, *F

400 500 600

. l I~ ELECTRIC POWERRESEARCH INSTITUTE


Evaluation of PWR Plant Shutdown withPressure Transient

40

35

30

25

20

15

10

E00~

(I,

0

000L..

.1.1U,

I- FAVOR Total KI

-- -- FAVOR Probabilistic Kmin

CPI = 7E-6CPF =3E-6TWCF < E-7

75F/hr CD from 550F to 250F, then 46F/hr CD to 175F, then hold at 175Ffor 12 hours, then CD at 26F/hr to 120F ,then CD at 6.8F/hr, pressure

transient to 1.17 ksi at 1OOF, then continue cooldown to 80F3% t = 0.2625" circumferential surface flaw

Cladding t = 0.25"Aspect ratio - 65

00 200 400 600 800 1000 1200 1400 1600 1800 2000

Time, minutes

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Conclusions

" Review of several plant operating pressure and temperaturetime histories indicate that startup and shutdown sequences donot occur on the Appendix G P/T limits.

" Protective devices provide additional assurance that normaloperation does not occur on or near the Appendix G P/T limits.

" The TWCF for LTOP event pressures up to the Appendix Glimits for normal reactor startup and shutdown are less than 1 E-7 per operating year.

* The conventional and RI-Appendix G allowable P/T limitsprovide adequate margins against RPV failure for the range ofpostulated flaws important to reactor safety, including 0.03tsurface breaking flaws.

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Together...Shaping the Future of Electricity

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Mark BurzynskiRolls-Royce

'Civil Nuclear Business, Instrumentation & Controls5959 Shallowford Road, Suite 511Chattanooga, Tennessee 37421

SUBJECT: AUDIT REPORT REGARDING THE ROLLS-ROYCE "SPINLINE 3 DIGITALSAFETY INSTRUMENTATION AND CONTROL PLATFORM" TOPICALREPORT (TAC NO. ME3600)

Dear Mr. Burzynski:

By letters dated July, 1, 2009, December 23, 2009, January 8, 2010, and February 2, 2010(Agencywide Documents Access and Management System (ADAMS) Accession Nos.ML092160017, ML093570361, ML100120087 and ML100330793, respectively), Rolls Roycesubmitted licensing topical report (LTR) "SPINLINE 3 Digital Safety I&C [Instrumentation andControl] Platform" and supporting documentation in accordance with Interim Staff Guidance(ISG) Document-06 to the U.S. Nuclear Regulatory Commission (NRC) staff for review.

The NRC Instrumentation and Controls Branch (EICB) conducted a regulatory audit onJune 11 - 15, 2012, at the Rolls-Royce facility in Grenoble, France. The audit results willprovide additional support for the safety evaluation of the LTR being conducted by the NRCstaff. The audit report is enclosed.

If you have any questions, please contact me at 301-415-4053 or by e-mail atJonathan. Rowley(5-nrc..qov.

Jonathan Rowley, Project ManagerLicensing Processes BranchDivision of Policy and RulemakingOffice of Nuclear Reactor Regulations

Project No. 773

Enclosure: Audit Report