Isolamento sismico degli impianti nucleari
Massimo FORNI - ENEA
Responsabile Unità Tecnica Ingegneria Sismica (UTSISM)
Giornata di Studio
LEZIONI DAL TERREMOTO DI TOHOKU
1 Luglio 2011, ENEA, Via Giulio Romano, 41, Roma
Cruas, France (1983-85), 4 PWRs - 3,600 Neoprene Isolators (500x500x65 mm)
Koeberg, South Africa (1984-85), 2 PWRs - 1,800 Neoprene bearings
(700x700x130 mm ) coupled with sliders
Kashiwazaki-Kariwa Nuclear Power Plant, strongly
damaged by the Niigata-Chuetsu-Oki earthquake
of July 2007, out of service for 3 years
La maggior parte delle centrali di II Generazione sono costituite da reattori ad acqua,
caratterizzati da una intrinseca resistenza nei confronti del sisma, e sono state progettate
con terremoti di riferimento non particolarmente severi.
ISOLATED REACTORS
“NEW” DESIGNS
ALMR
KALIMER
ESFR
PRISM
STAR-LM
4S
UPPER
BASEMAT
DFBR
ISOLATOR
REACTOR
VESSEL
Vertical Isolation
STAR-LM
DFBR
ESFR
Electrical equipments (and even whole control rooms) can be singularly
protected from the vertical component of the acceleration with suitable devices
3D devices
“vertical” devices
Examples of possible dispositions of energy dissipators within pipelines
to mitigate the effects of vertical accelerations
The Jules Horowitz Reactor, under
construction with seismic isolation at
the French Cadarache Nuclear Center
(same site where the ITER machine will
be built with isolation)
(mancanza di) NORMATIVA
Japan Electric Association (JEA), Nuclear Standard Committee of JEA, Design and
Technical Guideline of Seismic Isolation Structure for Nuclear Power Plant, JEAG 46142000 (in Japanese, only)
AASHTO - The American Association of State Highway and Transportation Officials,
Guide Specifications for Seismic Isolation Design, 2nd Edition and 2000 Interim
National Institute of Standard and Technology (NISTIR 5800), Guidelines for Prequalification, Prototype and Quality Control testing of Seismic Isolation Systems, 1996
NRC ???
EUROPA:
EN 15129, Anti-seismic devices
Validity of EN 15129 Anti-seismic devices could be
extended to nuclear plants with suitable changes, some
of them are minor, other are quite significant:
1) Limit to 100% the shear strain at the design earthquake;
2) Perform type tests on full scale isolators in real 3D dynamic
excitations up to failure
Eliminate the possibility of exceeding the isolator failure limit with suitable
horizontal fail safe system which damps the shock between building and lateral
foundation wall in case of extremely violent earthquakes (3-4 times SSE)
Expansion joints for pipelines
‘3-pins’ System made of 1 Angular and 2 Gimbals Expansion Joints
IRIS - International Reactor Innovative and Secure
50 m
1 m gap
1 m thick
Flood level (1 m)
56 m
23 m
21 m
22 m
Ground level
The last design solution foresees 99 HDRBs of 2 diameters (1000 & 1300 mm), 100 mm
rubber height and 1.4 MPa rubber shear modulus. The stiffness centre of the isolation
system coincides with the center of mass of the structure so to avoid eccentricity effects
(rotations around the vertical axis). During earthquake the building moves like a rigid
body with the same acceleration at any level (no amplification).
Behavior of the isolated IRIS building under the design 3D earthquake (0.3g
peak). The structure behaves like a rigid body (same acceleration from the base
to the top) withTime
0.2
g max acceleration and 10 cm max displacement.
history X+Y+Z
2.5
Dir X roof
Dir X isolator
2
Dir X vessel
1
0.5
0
0
5
10
15
20
25
-0.5
-1
-1.5
Time history X+Y+Z
-2
Time (s)
0.1
Dir X roof
Dir X isolator
0.08
Dir X vessel
0.06
0.04
Displacement (m)
Acceleration (m/s2)
1.5
0.02
0
0
5
10
15
-0.02
-0.04
-0.06
-0.08
-0.1
Time (s)
20
25
The isolation system can reduce the acceleration of the building (and then the
inertial forces on the components) by a factor 1.5 ÷ 2 at the vessel
attachment level and even 5 ÷ 6 at the roof level.
12
ROOF (fixed base)
GROUND (~ Vessel)
9
ISOLATED BUILDING
Acceleration (m/s2)
6
3
0
-3
-6
-9
-12
0
2
4
6
8
Time (s)
10
12
14
Preliminary cost analysis made by ENEA for IRIS:
- The cost of the whole isolation systems ranges between
1.5 and 1.8 M€ (FIP Industriale S.p.A, Padova, Italy - devices manufacturer)
- The cost analysis of the qualification and acceptance tests is still in progress
(it could be 0.1 M€, but it will strongly depend on the final number of isolators, the standard used …...)
- No significant costs are expected for maintenance and inspection
(replacement of isolators is not necessary even after the design earthquake)
-The cost of the sub-foundation and lateral containing wall (for a medium soil) is
5 ÷ 7 M€
(Achille Fadalti S.p.A., Pordenone, Italy - construction company)
- The cost of the expansion joints for the 8 pipelines is
0.5 M€
(BOA BKT GmbH, Stutensee, Germany - joints manufacturer)
TOTAL COST: 9 ÷ 10 M€
CONCLUSIONI
Cause che giustificano il limitato numero di impianti nucleari isolati sismicamente:
1) Input sismico relativamente basso assunto nel progetto degli impianti di II
Generazione (0.2 g), la maggior parte dei quali è composta da reattori ad acqua,
dotati di una buona robustezza intrinseca;
2) Impossibilità di proteggere l’impianto dalla componente verticale del sisma,
almeno allo stato tecnologico attuale;
3) Carenza di normativa specifica;
4) Costi (necessità di realizzare una sottofondazione aggiuntiva, una parete di
contenimento del terreno per la parte interrata, giunti di dilatazione, ecc…).
Necessità future che richiedono OBBLIGATORIAMENTE l’applicazione dell’isolamento:
1) Affrontare input sismici sempre più severi;
2) Garantire standard di sicurezza sempre più elevati, specialmente nei riguardi di
eventi che vanno oltre le condizioni di progetto (beyond design);
3) Garantire una sempre più spinta standardizzazione dell’impianto.
SILER (Seismic-Initiated events risk mitigation in LEad-cooled Reactors)
Type of funding scheme:
Collaborative Projects (CP): Small or medium-scale focused (CP-FP)
Work programme topics addressed:
Call Identifier: FP7-Fission-2011
Activity/Area: II.2.2.3: Cross-cutting aspects for nuclear systems
Topic: Fission-2011-2.3.1: R&D activities in support of the implementation of
the Strategic Research Agenda of SNE-TP
Partners
ENEA (Coordinamento), AREVA, SCK-CEN, FIP Industriale, MAURER-SOEHNE,
JRC Ispra, SINTEC, KTH, BOA, IDOM, ANSALDO NUCLEARE, IPUL, NUMERIA,
VCE, SRS, EA, CEA, NUVIA
External Advisory Committee
(EdF, ENEL, NRC, IAEA, KIT, NPS, UCSD)
GRAZIE PER L’ATTENZIONE
[email protected]