davis-besse nuclear power station reactor vessel incore nozzles

8/3/2019 Davis-Besse Nuclear Power Station Reactor Vessel Incore Nozzles

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DavisDavis--BesseBesse

Nuclear Power StationNuclear Power StationNovember 26, 2002November 26, 2002

Davis-Besse Nuclear Power Station

Reactor Vessel Incore Nozzles


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Opening Remarks . . . . . . . . . . ....Gary Leidich

Reactor Vessel Incore Nozzles. Bob Schrauder

Incore Nozzle Configuration

Recent Inspection and Evaluation at Davis-Besse

Actions Prior to Returning the Plant to Service Contingency Repair Concept

FLS Online Leak Monitoring SystemClosing Comments.. Gary Leidich


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Gary Leidich

Executive Vice President - FENOC


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Brief the NRC Staff on the status of the Davis-Besse Reactor Vessel Incore MonitoringInstrumentation Nozzles and future plans

Obtain NRC comments on Davis-Besse approach


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CEO of FirstEnergy

has set the standard of returning

Davis-Besse

back to service in a safe

and reliable manner.

We must do the job right the

first time and regain theconfidence of our customers,

regulators, and investors in our

nuclear program.

We are committed to meeting

this challenge.


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Reactor HeadReactor HeadResolution PlanResolution Plan

Bob SchrauderBob Schrauder

Program ComplianceProgram Compliance

PlanPlan

Jim PowersJim Powers

Containment HealthContainment Health

Assurance PlanAssurance Plan

Randy FastRandy Fast

Restart Test PlanRestart Test Plan

Randy FastRandy Fast

Management andManagement and

Human PerformanceHuman Performance

Excellence PlanExcellence Plan

Lew MyersLew Myers

System HealthSystem Health

Assurance PlanAssurance Plan

Jim PowersJim Powers

Restart Action PlanRestart Action Plan

LewLew MyersMyers

Restart Overview PanelRestart Overview Panel

Return to Service PlanReturn to Service Plan


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Inspection of the Incore Nozzles is part of the

Containment Health Assurance Building Block in theDavis-Besse Return to Service Plan


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Bob Schrauder

Director - Support Services


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Babcock & Wilcox reactorvessel has 52 Incore Nozzles

Incore nozzles are ~ 1 inchin diameter

Original incore nozzles

fabricated from Alloy 600material Welds - Alloy 182 (stress

relieved)

Incore nozzles modifiedfollowing Oconee 1 1972 HotFunctional Testing Failure

Configuration

Incore Nozzles

at Bottom of Reactor Vessel

(Post-cleaning)


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Repair in Process Completed Repair


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Incore nozzles are exposed to lower temperature (558oF) thanControl Rod Drive Mechanism nozzles (605oF) and are lesssusceptible to stress corrosion cracking

Visual inspections of the incore nozzles have not been routinelyconducted in United States plants

Inspections/testing of incore nozzles at 13 French plants have not

discovered cracking or leaking

Incore Nozzles


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B&W Current Nozzle ConfigurationEDF Nozzle Configuration

Original Configuration


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Visual Inspections performedas part of the Extent ofCondition Program

Inspection of Bottom of Reactor Vessel


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Inspection results: Boron and rust deposit trails

were observed on the sides and

bottom of the reactor vessel Similar deposits observed on

several incore nozzles

Tape remnants and residueobserved on incore nozzles

No build-up of boric acid or

corrosion products on top ofinsulation

No evidence of wastage on

bottom of reactor vessel

Bottom of Reactor Vessel


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Incore Nozzle #42

Incore Nozzle #45


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AREAS:

Reactor vessel flow trail and incorenozzle deposits

OBJECTIVE: Determine through chemical analysis

whether flow trails and incore nozzle

deposits had common sourceSAMPLE POPULATION:

2 from flow trails observed on under

reactor vessel sides

12 from incore nozzles

Analysis by Framatome-ANP Incore Nozzle #45

Bottom of Reactor Vessel


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Sample locations ( ) chosenwere nozzles

1

7

3

13

14

18

23

27

35

45

48

46


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Boron and Lithium were higher at several incore nozzle locationsthan in flow trails and more comparable with previously analyzedupper head deposit samples (shown next slide)

Minor species (Uranium, Barium, Thorium, Strontium, & Zirconium)

were higher at several incore nozzle locations than in the flow trails.

However, the lack of activity associated with these species did notsupport reactor coolant as the source

Cobalt (Co60) and Iron (Fe59) were higher in the flow trails than at theincore nozzle locations

Inconsistent concentration gradients along possible flow trail paths


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NWRustTrail

SEBoricAcidTrail

Nozzle#1

Nozzle#3

Nozzle#7

Nozzle#13

Nozzle#14

Nozzle#18

Nozzle#23

Nozzle#27

Nozzle#35

Nozzle#45

Nozzle#46

Nozzle#48

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

ppm

Comparison of Normalized Boron and Lithium Concentrations

(Flow trails at bottom of reactor head and incore nozzle deposits)

Li

B


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Conclusion

From the results of the analysis,it is inconclusive whether the flow trails at the bottom of the

reactor head and nozzle deposits had a common source


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FENOC and Framatome-ANP developed inspection plan

Bottom of reactor vessel thoroughly cleaned 9/2002 Planned visual inspections prior to startup:

Raise Reactor Coolant System to normal operating pressure and

temperature (hold for 3-7 days) Potential use of hot optics (visual inspection aid)

Lower temperature and pressure

Perform bare metal reactor vessel visual inspection Perform bare metal reactor vessel visual inspection during the next

scheduled outage


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0.001

0.010

0.100

1.000

10.000

100.000

1000.000

1.00E-06 1.00E-05 1.00E-04 1.00E-03 1.00E-02

Leakage Rate (gpm)

BoricAcidDeposits(in3)

35 Day

28 Day

21 Day

14 Day

10 Day

7 Day

3 Day1 Day

FLUES OPTION 1

FLUES OPTION 2?

Boron Deposit Rate For 2000 ppm Boron Reactor Coolant Leakage(Unchoked Flow) 100% Deposition Rate

For a Given Number of Days


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Inspections will be sufficient to detect leakage

Absence of boric acid will confirm that the deposits found inin 2002 were not from incore nozzle leaks


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Program Objectives Measure leak rate as a function of simulated and/or actual flaw

geometry

Benchmark analytical models for bounding leak ratecalculations

Identify residue deposit chemistry and any volatile chemicals

that exit the crevice

Investigate effect of annulus on leakage rates

Verify methods for detecting very small leaks Visible evidence of boron residue

In-situ monitoring techniques


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Framatome-ANP Hot Leak TestFacility will be used to provide

primary fluid: Tc = 558 F; p = 2200 psig

Primary chemistry (boron &

lithium concentration) Mockup assembly will be

connected to existing hightemperature/ high pressure

supply system Leak rates measured from 10-6

to 0.25 gpm


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Mockup is being designed and built to measure leak ratesthrough simulated (SCC) flaws

Leak rate bounding tests will be conducted for 8 hours each

Final test with a selected leak rate will be run for 5 days


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Insert mechanical plug and

cut existing incore nozzle Deposit 1/2 - 5/8 weld pad

Bore out incore nozzle

remnant into reactor vessel to1 maximum depth

Fit-up replacement nozzle

and complete new weld Remove mechanical plug

1/16" - 1/8" prior to welding

PT

New Alloy 690 Nozzle

New SST Safe End


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If repairs are necessary, a meeting to discuss final design will beheld with the NRC

10CFR50.55a alternative code (ASME Code Section XI)requests will be necessary to permit implementation of repairs

Alternative code request will be similar to those submitted toNRC for the repair of Control Rod Drive Mechanism nozzles atother plants


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Davis-Besse plans to install FLS Online Leak Monitoring System

Ability to detect and locate leakage with significantly highersensitivity than other available systems

Leak detection system measures the moisture penetrating a sensor

tube Installed or being installed in 12 units in a variety of Europeancountries and Canada

Operational history of 10 years


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Sensor Element

Non-Sensitive Tubing


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Install sensor tubebetween the reactor vessel

insulation and reactorvessel

Simple installation

Expected sensitivity ofapproximately 4E-3 to 2E-2 gpm

System sensitivity isdependent on the airtightness of reactor vesselinsulation

FLS

SENSORS

RVInsulation


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DavisDavis--BesseBesse No ember 26 2002November 26 2002

Gary Leidich

Executive Vice President - FENOC

davis-besse nuclear power station reactor vessel incore nozzles

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