International Workshop of the SILER Project on Seismic ... SRS Garigliano.pdf · Ø Set up of a detailed 3D FEM based on the 3D CAD model: (a) Taking into account structural joints

EC Collaborative Project SILER: Seismic-Initiated events risk mitigation

in LEad-cooled Reactors

THEME: Fission 2011-2.3.1: R&D activities in support of the implementation of the Strategic Research Agenda of SNE-TP

Grant Agreement 295485

October 1st, 2011 - September 30th, 2014

International Workshop of the SILER Project on

Seismic Analysis of Lead-cooled Reactors

Seismic Risk in decommissioning stage - Two case histories 1. Seismic Risk and decommissioning: focus on Garigliano and Latina NPP P. Palumbo2. Latina NPP – Seismic assessment and upgrading of reactor building G. Moretti3. Garigliano NPP - Seismic assessment and upgrading of turbine building G. Barbella

Aims: (1) To provide an overview of the approach adopted in Italy to manage seismic risk during the

decommissioning stage of nuclear power plants;(2) To discuss possible advantages attainable in decommissioning stage by using innovative seismic

upgrading techniques (base isolation and supplemental damping);(3) To outline, hopefully, a future field of research.

Seismic Risk in decommissioning stage - Two case histories

September 2014 P. Palumbo, G. Moretti, G. Barbella 2

LATINA NPP: Seismic assessment and upgrading of reactor building



GENERAL ASPECT AND STRATEGIES

The seismic evaluation of the Reactor Building is aimed at:

Ø Evaluating seismic safety of the building;

Ø Defining the possible upgrading strategies in view of future uses;

Ø Preliminary design of retrofitting actions.Many tasks have been accomplished; the most important are:

Ø Set up of a detailed 3D CAD model including: (a) architectonical layout;(b) civil and mechanical component;(c) structural feature (columns, beams, walls, slabs and connection joints);(d) data base with all material information and main component characteristic ( material,

geometry, weight etc).

Ø Surveys, investigations and study of the original documentation (as built drawings);

Ø Set up of a detailed 3D FEM based on the 3D CAD model:(a) Taking into account structural joints(b) Soil Structure Interaction

Ø Safety assessment:(a) Seismic evaluation(b) Definition of optimal upgrading actions(c) 3D FEM analysis in the upgraded configuration(d) Preliminary design (drawings and reports)



GENERAL ASPECT AND STRATEGIES

THE PURPOSE OF THE 3D CAD MODEL IS:

Ø Collecting all the available information into an effective data base(original documents, technical reports, drawings and calculation notes);

Ø Easiest retrieving of information during decommissioning stage;

Ø 3D FEM set up;

Ø Fast elaboration of new drawings. THE PURPOSE OF THE 3D FEM MODEL IS:

Ø Detect possible structural criticalities;Ø Design of seismic retrofittingØ Future evaluations aimed at the construction of new inner facilities;



3D CAD MODEL: description

BUILDINGConcrete and Steel structures

CONCRETE BIOLOGICAL SHIELDINGMassive concrete walls and dome

VESSELPipes, and mechanical components

CORESteel supporting structure and graphite

The 3D CAD model has been developed using five different softwares:

1. Autocad for civil components;2. Catia for mechanical components

using a parametric approach for the geometry definition;

3. Hypermesh for the simplification of whole model needed for the 3D FEM set up;

4. Microsoft Access for the DATA BASE (linked with the whole model);

5. 3D Studio max for Renderings and Animations



3D CAD MODEL: Rendering



3D FEM: MODEL AND ANALYSIS

1° STEP The FEM model is set up, by

simplifying the CAD model,

considering middle surface of

the walls and axis line for

columns.

Non-structural components

have been included in terms of

masses. 2° STEPStructural main features, i.e.

joints, constraints, and masses,

are identified.

3° STEPAppropriate finite elements

(1D, 2D, 3D, kinematic links

between elements, …) are

selected and the numerical

model is realized.

To reproduce SSI effects a

portion of soil is explicitly

modeled.

4° STEPModal analysis of the

whole model is performed.

More than 1000 modes

are extracted to explore

and understand the

combined behavior of

concrete and steel

structures.5° STEPResponse spectra analysis is

carried out to obtain stress

distributions and to find out

possible pounding between

faced elements.

6° STEPSoil bearing capacity is

assessed



3D FEM MODEL: GENERAL DESCRIPTION

GENERAL DATA OF THE FE MODEL:

Ntot. Elem = 235350Ntot. Joint = 233307N. Solid Elem = 84824N. Shell Elem = 131115N. Rigid Elem = 54N. 1D Elem = 12948N. Masses = 5341N. Link = 1068 TOT = 235350

SOFTWARE:

PRE PROCESSING:

- HYPERMESH 10.0 (Altair)

- Fx+ FOR DIANA

POST PROCESSING:

- TNO DIANA (Main Software)

- ABAQUS STANDARD

( Indipendent check )

SOIL STRUCTURE INTERACTION MODELLING

BUILDING SOIL

CONSTRAINED SURFACE

80m

132m114m

FEM DESCRIPTIONThe whole model has been set up

considering the building, mechanical

components and a part of soil

(114x132x80m) in order to take into account

the soil structure interaction. Soil properties

have been recovered from geological

surveys.

Rigid elements and special links have been

used to represent the structural joints and

an appropriate connection between

elements with different dofs (ex. Connection

between bricks and beams)

GENERAL VIEW OF THE REACTOR BUILDING

GENERAL VIEW OF THE VESSEL AND INTERNAL



3D FEM MODEL: REACTOR BUILDING

The conduit concrete shields are simply supported by the boiler steel frame and the concrete CO2 duct walls.In order to represent the real kinematic mechanism, the connection has been modeled adopting appropriate link elements.

CONCRETE BIOLOGICAL SHIELD DOME VIEW 3D SECTION

SOUTH PART

EAST PART

SHIELD

JOINT

CO2 DUCTS COMPARTMENTS

CONDUIT CONCRETE SHIELD

Rigid Beam

ShellSolid

Embedded Elem.



3D FEM MODEL: VESSEL AND INTERNAL

SCHEME OF VESSEL SUPPORTING STRUCTURE CONSTRAINS

Cylindrical inges

Rods

Vessel

Each column is provided with top and bottom cylindrical hinges to allow for the thermal expansion of the vessel avoiding thermal overstresses.The model reproduces this type of constraint.

STANDPIPES

CORE SUPPORTING GRID

3D CAD MODEL RENDERING

3D CAD MODEL RENDERING



MAIN RESULTS

1° RESULT CO2 ducts compartments

undergo excessive stresses

under the design earthquake.

2° RESULT In the vessel supporting

columns earthquake actions

cause locally tensile stresses

greater than the steel yield

limit.

3° RESULT The peak soil pressure is

0.6MPa. The value is lower

than the soil bearing capacity.

4° RESULT Standpipes undergo local

yielding.

Excessive displacements cause

pounding between standpipes

and the steel channels

embedded into the vault of the

concrete biological shield.5° RESULTSteel auxiliary structures

surrounding the boilers are

overstressed due to the conduit

concrete shield masses.

6° RESULTThe south wing is constituted by

columns and beams constrained

by means of sliding supports to

the biological shield.

Large relative displacements

between beams and biological

shield cause overstresses in the

columns.

COLUMNS NOT VERIFIED



Main detected criticalities:

q CO2 ducts compartments (FLUMES)q columns and walls of control and fuel bodies

above level +22.55q steel structure of boilers’ framesq standpipesq Vessel support columns

ANTE OPERAM CONFIGURATION: VULNERABILITIES

Summary of results obtained for earthquake Tm=1000 years



PLANNED WORKS ON THE BUILDING STRUCTURE

ü Removal of CO2 ducts upper shields (boiler shields),ü Removal of boilers and CO2 blowers,ü Removal of the steel structure used for the boilers maintenance,ü Height reduction of the of the CO2 ducts compartments walls,ü Closure of the gaps between the concrete biological shield and the surrounding structures

INTERVENTION PROPOSAL - PRELIMINARY PROJECT

GAPS CLOSURE

DEMOLITION AND REMOVAL



INTERVENTION PROPOSAL - PRELIMINARY PROJECT

PLANNED WORKS ON THE REACTOR COMPONENTS

ü Connection between standpipes and concrete biological shield domeCONCRETE

MORTAR

STANDPIPES



4.25 Hz

2.25 Hz

3D FEM MODEL AND ANALYSIS: POST OPERAMPOST OPERAM 3D FEM MODAL ANALYSIS

(Global Reactor Building Mode Shape)

MODAL ANALYSIS(Global VESSEL Mode Shape) RESPONSE SPECTRUM RESULT

CRITICAL COMPONENTS



MAIN RESULTS

σmax = 11.58 MPa

σmax = 2.15 MPa

σmax =275 Mpa σmax =180 Mpa

WALLSThanks to the height

reduction of the CO2 ducts

compartments, vertical

stresses in concrete are

strongly reduced.

From 11.58 MPa to 2.15 MPa

STANDPIPESPounding phenomena are

eliminated.

Peak stresses in the

standpipes are reduced

from 275MPa to 180MPa.

SUPPORT COLUMNSHigh stresses in steel columns

are reduced from 200MPa

(widespread over the volume

of each one) to 170 MPa (local

peaks only).

σmax =200 Mpa σmax =170 Mpa

standpipes



q An accurate FE model of the reactor building has been set up based on a very detailed 3D CAD model which collects the large amount of dispersed information.

q The finite element model has been used for the seismic safety evaluation. Results obtained pointed out structure vulnerabilities.Conventional upgrading actions have been conceived and verified with an updated finite element model.

q Conventional seismic upgrading techniques leads to heavy demolition and lengthy construction time.

q Seismic design of new NPP should better take into account the long duration of the decommissioning stage.To this aim the adoption of advanced and innovative technologies for seismic mitigation (seismic isolation in two/three direction) could be explored.

CONCLUSIONS

Documents

International Workshop of the SILER Project on Seismic ... SRS Garigliano.pdf · Ø Set up of a detailed 3D FEM based on the 3D CAD model: (a) Taking into account structural joints