In-Service Inspection &Repair of Sodium Cooled Reactors General strategy and feedback experience

October 2005 1DTN/STPA/LTTSISI&R_Rosatom_FB2005

•In-Service Inspection &Repair

of Sodium Cooled Reactors

General strategy and feedback experience

F. Baqué

DEN Cadarache


Objective Underlining the ISI&R aspect

of sodium cooled reactors :

In service inspection plan must be defined

Definition of ISI as Design confirmation tool

Checking damage evolution of structures :

- cracks absence or sizing

- failure and component position detection

- migrant piece detection

- corrosion and tightness checking

- buckling, creep effects, mesalignment


Main and guard vessels

Core supporting structures (diagrid…)

Component skirts

Above core structure

Pump to diagrid pipe

Control rods / assemblies alignment

Secondary circuits & components

BackgroundFrench and international feedback experience

of existing sodium cooled Fast Reactors

(mainly Phénix and Superphénix Plants, but also Monju)


Background

Studies for innovative projects

(mainly EFR, but also ALMR, DFBR, BREST-300)

USA

Russia


ISI&R parameters

- Available ISI&R tools & techniques : ISI : US, EMAT, visual … waiting for under sodium

telemetry and NDT ? Repair : sodium sweeping, cutting, TIG welding, laser…

- Design simplicity as regards ISI&R needs : Simple shapes for access to sensitive zones Low stress, design margins to lower damage Few and shorter welding joints to be inspected

- Access facility to internal structures and components : Specific channels Removable parts


ISI&R parameters (continued)

- Reactor conditions : Temperature, aerosols, radiation, air ingress risk…

- Reactor size : « the larger, deeper, longer it is, the harder ISI&R »

- Structure characteristics : Geometry (length, diameter, thickness…) Material (laminated/forged, sensitivity to cracking, wetting)

- Modularity : Operating when a module is in shut down conditions

for inspection and/or repair- Easily removable parts :

for easier and full inspection and/or repair


ISI parameters : application to EFR project


Large inspectionMedium inspection

Low inspection

Seriousnessof

damage for safety

No inspection

Cumulated potential damages

hight

medium

low

low medium hight

ISI codes and standards

•The « potential damage method » : for each structure

•Limited to ASME section XI division 3


ISI codes and standards

•« potential damage method » :Large

inspection

Medium

inspection

Low inspecti

on

No inspecti

on

Initial damage Time

Cumulated damage

Real damage

Estimated damage

Revised along plant life (all situation counting)

Initiated at the design phase calculation of damages evaluation of failure effects


Potential damage method : application to Superphénix

safety vesselslab connectionheterogeneous

welding

premary vesselslab connection

platelagesupporting shell

diagrid supportlateral supporting

zone

core support plateboxessupport weldingtables

connecting pipebetween pumpand diagriddiagrid inletpump outletpump support

control rodalignment

roof slab androtating plugrotating plug

supportcomponent

support

boxes

above corestructureheadsodium free levelexternal shirtwelding

High surveillanceIntermediate surveillanceLow surveillance


ISI at the Design phase

An iterative process :

Preliminary ISI evaluation of SFR concept

More detailed ISI&R requirements

Identification of priorities and recommendations

SFR consistent design

1

2

3

4


ISI&R criteria at Design stage :

Proposal for ISI&R criteria utilization at Design stage

8 ISI&R criteria

(1)

ISI&R operation

quality

(2)

ISI&R operation duration

(3)

ISI&R operation

means

(1)+(2)+(3)

ISI&R operation

risks

Notation along

feedback experience

+ o -

ISI results = defect detection

and sizing, image

recording, télémtry

measures…

ISI operations sometimes longer than expected

(technical or human

problems)

ISI operations with staffs and tools (robots,

sensors…) to be

available

Risks :

of poor result quality

of over-duration

of technical or human

difficulties…


ISI&R criteria at Design stage :

quality

duratio

n

means

Less important : Reactor size o + o Structure characteristics + - -

Very important : Tools & techniques + + + Design simplicity o + + Access facility o + +

Not so important : Modularity o - - Easily removable parts o o o Reactor conditions o - -


Inspection of gas coverture :visual control above sodium free level

Phenix primary vessel inspection : visual checking after partial primary sodium draining

In sodium qualification tests


R&D for the Inspection of immersed structures :in sodium ultrasonic telemetry

in water qualification


Inspection of core supporting structures :Phénix experience

Ultrasonic inspection of 4.5 m long shell (immersed in sodium)


Repair of removable componants :handling out of primary vessel

Handling of the drilling machine for Superphénix core catcher piercing : mechanical process 20 m long machineThrough roof penetration Under sodium operation 3 year developt & qualification


In-Service Inspection of Superphénix PlantPrimary Vessel Welds : the Rapid Inspection

Machine (MIR)

Primary vessel

Guard vessel

2 cameras

US sensors

700 mm


Repair of immersed structures :Superphénix experience

Repair of IHX argon feeding tube (1995)

Leak zone


Core outlet sodium behaviour :Superphénix acoustic monitoring

6 metallic bars within above core structure

Control rod impact

Argon in primary sodium


Tube bundle inpection and repair :Superphénix SGU

Ultrasonic probe for Superphénix steam generator tubes


R&D for Repair : welding after sodium trace removal

Nettoyage sans asservissement

1 passage

2 passages

3 passages

• Laser sodium

sweeping. maxi. 40 W

. 12 ns pulses

. 120 Hz

. 3,5x3,5 mm2

. 45 to 1100 mm/mn

• TIG welding after sodium

removal


Pool / loop comparison

The comparison depends on general review of ISI approach : 8 above mentionned criteria have to be taken into account

» potential damage » approach has to be undertaken in every case

As a general matter : Pool concept : favouring design simplicity, but more

difficult access (larger size and integrated components)

Loop concept : favouring access facility, but more components to be inspected (3 vessels instead of 1, primary pipes, valves…)

Documents

In-Service Inspection &Repair of Sodium Cooled Reactors General strategy and feedback experience