ML062290208

Meeting Slides Tornado and High-Energy Line Break Mitigation Strategies

ML062290208
Person / Time
Site:	Oconee
Issue date:	07/26/2006
From:	Duke Energy Corp, Duke Power Co
To:	Office of Nuclear Reactor Regulation
Olshan L N, NRR/DORL, 415-1419
Shared Package
ML062290237	List: ML062200043 ML062290208
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Download: ML062290208 (11)

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P Duke Duke Energy Oconee Nuclear Station HELB/Tomado Mitigation Strategies Meeting NRR Offices Rockville, MD July 26, 2006, 10:00 a.m. - 12:30 p.m.

1 Enclosure 2

Duke Energy,. Duke Attendees Larry Nicholson Rich Freudenberger Graham Davenport

- Jim Sumpter

Jeff Robertson

- Allen Park Tim Brown Lee Kanipe Steve Newman Keith Graham 2

POEnergy.

Duke Agenda Opening Remarks c Duke Responses to NRC Items from the July 12, 2006 HELB / Tornado Strategies Letter.

Enclosure 1 Discussion Closing Remarks 3

kDuke Opening Remarks 4

4

Duke Item 1: Use of TORMIS

• Conditions outlined in the October 26, 1983 TORMIS methodology

• Atmospheric Dump Valves (ADVs) access

" Duke concurs that TORMIS must collectively assess probability of damage on a function basis

" Criteria for physical separation

• Applicability of TORMIS to ONS

" Planned modifications 5

Physical Separation In resolution of Systematic Evaluation Program (SEP) ISSUE 156.1.5, the NRC acknowledged that there was no guidance relative to missile protection prior to 1972.

Physical separation was approved by the NRC as part of the Oconee SER (Unit 1, Section 6.2, page 34, last paragraph).

Physical separation was outlined as an acceptable approach in NUREG-75/087 (Standard Review Plan)

Section 3.5.2, "SSCs to be Protected from Externally Generated Missiles", Item III, next to last paragraph, dated 11-24-75.

Intended Use of TORMIS.

October 26, 1983 TORMIS Methodology SER indicates TORMIS to be used to offset large expenditures.

November 7, 1983 NRC memo from Denton to Stello tied use of PRA for tornado missile analysis to function (Oconee effort cited in first paragraph):

Based on the guidance In SRP Sections 3.5.1.4 and 2.2.3, we plan to permitapplicants and licensees to use risk assessments for tomado and otherhiph wind missiles and to judge theiracceptabilityagainsta numerical criterion which is as follows: The probabilityof significantdamage to SSCs requiredto prevent a releaseof radioactivityIn excess of 10CFR Part 100 following a missile strike, assuming loss of offsite power,shall be less than or equal to a median value of E-7peryearora mean value of E-6 peryear. Significant damage is damage that would prevent meeting the design basis function....

Applied to ONS secondary heat removal function In post-TMI EFW ONS SER dated July 28,1989.

Applicability of TORMIS Methodoloov to ONS.

SEP NRC GL 95-04, 4/28/95, ISSUE 156.1.5: TORNADO MISSILES:

This issue is one of the nineteen Category3 issues identifiedby NRR in SECY-90-343. All plants licensed after 1972 were designedfor protection againsttornadoes. The concern existed,however, that plants constructedpriorto 1972 may not be adequatelyprotected,in particular,those reviewed before 1968 when criteria on tornadoprotection were first developed ..... Thus, the staff beieves that any vulnerability associatedwith tornado missiles will be evaluated and reportedin the IPEEEsubmittals.

ONS was one of the 41 plants.

IPEEE dispositioned missiles using TORMIS. NRC issued SER for ONS IPEEE on March 15, 2000. There were no outstanding Issues other than protection of emergency response personnel.

Also used to address post-TMI EFW tornado issue. NRC issued SER on July 28, 1989.

5

Duke Item 2: Cold Shutdown

• Protected Service Water (PSW) and SSF capability -

maintain hot standby for up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />

• Initiate plant cooldown to -250 degrees F

• Cold shutdown following damage repair

- Systems

- Vulnerabilities

" Human Factors Assessment

- Time critical actions will be in EOPs

- CSD is not time critical

- Damage repair guidelines

- Time to achieve CSD will be based on damage assessment and repair 6

6

Duke Item 3: Technical Specifications

• Incorporation of new PSW system LCOs and AOTs should and will be included in a controlled regulatory document

" PSW to be incorporated into SLC manual (a.k.a. TRM)

- New PSW system does not meet the 10 CFR 50.36 criteria

- New PSW system and functions not in NUREG 1430

- Preliminary PRA results - medium risk system

- LCO and AOT times to be determined using PRA analysis

" Maintenance Rule criteria will ensure that stringent controls for system availability for all tornado and HELB mitigating systems are met.

7 7

Duke Energy,, Item 5: Application of GL 87-11

• Duke will fully apply criteria for intermediate pipe ruptures per GL 87-11

• Duke will utilize the following MEB 3-1 criteria:

- No Class 1 piping outside containment

- Will apply to postulated pipe breaks and critical cracks in all seismically analyzed lines

- For leakage cracks:

• Auxiliary Building - will be postulated

• Turbine Building - will not be postulated

- Moderate energy cracks will not be postulated

- Circumferential and longitudinal breaks and crack orientations will be adopted 8

The power piping code of record at Oconee is the USAS 831.1 code.

8

Duke Item 4: Reactor Coolant System Energy. Letdown Line

" For HELB: Evaluation approach

- Probability of break is low

- Relocation of pressure reducing orifice impractical

- Validation of results of original HELB report

- Critical cracks (will use MEB 3-1 criteria)

" For Tornado: Missile damage resulting in concurrent LOCA is not credible based on physical construction and configuration 9

HELB The Safety Evaluation Report (SER) for Units 2&3 (dated 7/6173) approved the original HELB report and noted that protection was to be provided for fluid piping systems that exceeded 200 degrees F and 275 psig. The letdown line at the containment penetration is at 120 degrees F and 2160 psig and thus is not technically a high energy line. The SER acknowledged the following: "The reactor coolant letdown is cooled before leaving the reactor building so this system is essentially a high pressure system rather than a high pressure and high temperature system."

Credible Tornado Threshold for Later Plants Around 1E-7 Staff objective outlined in SRP Section 2.2.3, Rev. 2.

Endorsed in ANSI/ANS 51.1-1983: Nuclear Safety Criteria for the Design of Stationary Pressurized Water Reactor Plants 9

SDuke Item 6: Protection of Electrical Energy, Penetrations Electrical penetration enclosures housing circuits necessary for safe shutdown (SSD) will be protected from jet impingement and spray:

- East Penetration Room - jet impingement and spray

- West Penetrations Room - jet impingement only

• Other enclosures housing circuits in the East Penetration Room, whose failure or inadvertent operation due to spray could impact SSD capability, will be protected from spray.

10 10

P Duke Closing Remarks 11 11