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  • Luis YageLuis YageDeputy General DirectorDeputy General DirectorAsociacinAsociacin Nuclear Nuclear AscAsc VandellsVandellsColoniaColonia, 30/05/06, 30/05/06

    Action Plan to improve systems and organizational Action Plan to improve systems and organizational

    performance as a result of the performance as a result of the EssentialEssential ServiceService WaterWater

    SystemSystem IncidentIncident in Vandells II NPP.in Vandells II NPP.

  • 2

    Vandells II site

    Garoa

    Vandells IITrillo I

    J. Cabrera

    Cofrentes

    Almaraz I & II

    Asc I & II

  • 3

    Vandells II site

  • 4

    Vandells II performance data

    Vandells II Year Comercial Operation 1988

    Reactor Type W PWR 1087 Mwe

    GROSS ELECTRICAL PRODUCTION (GWh)

    0

    2000

    4000

    6000

    8000

    10000

    C.N. Asc I 5798 8239 6645 7629 8472 8012 8121 8796 7927 8075C.N. Asc 2 7042 6179 8161 7689 7511 8795 8159 8152 8887 7238C.N.V. II 7876 7827 7559 8717 7528 8305 9376 8351 8560 9032

    1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

  • 5

    Vandells II performance data

    CAPABILITY FACTOR

    0

    20

    40

    60

    80

    100

    C.N. ASC 1 71,4 99,3 81,6 90,2 99,3 89,9 91,2 97,67 87,74 89,03C.N. ASC 2 86,7 75,6 99,4 91,2 88,1 98,7 92,1 90,59 98,77 80,22C.N.V. II 90,1 89,2 89,2 99,3 83,3 87,4 99,5 87,7 89,88 94,58

    1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

  • The The IIncidentncident & the & the SSystemystem

  • 7

    What happened?

  • 8

    What happened?

    On August 25, 2004 at 5:25 a.m. Vandells II suffered a circumferential break on a manhole neck (EF-18-I) when starting-up pump EF P01 C

  • 9

    The Incident & the System

    TurbineSpent fuel

    Auxiliar

    Cont.

    Control

    D.G.B

    D.G.A

    A C B

    Com

    pone

    ntC

    oolin

    gB

    Impulsion train B

    Return train B

    Impulsion andReturn train A

    ESWS layout. Supports Component cooling, Essential Diesel Generators cooling, and Chilled water cooling.

    External piping: Buried BONNA pipe.Inside buildings: Carbon steel with epoxi liner >3. SS or Monel

  • 10

    The Incident & the System

    After identifying external corrosion in the presence of chlorides as the cause for rupture of the neck, all the remaining necks were inspected except the symmetric ones on the other train that had already been repaired. To a different extent all necks had degraded painting and corrosion.

    (In no case was the remaining neck wall thickness less than 2mm).

    Lateral view, piping andman-hole of ESWS

    Chest elevation, pipingand man-hole of ESWS

  • 11

    The Incident & the System

    Repair done in the two lower necks locateddownstream from the pumps on each train.

    Corroded zone

  • 12

    The Incident & the System

    Afterwards, and due to the presence of humidity on some necks, temporary repairs were performed on all of them. This was carried out by reinforcing such with bars welded to the neck flanges and reinforced concrete.

  • 13

    The Incident & the System

    During the refueling outage, external corrosion was seen on some zones of the internal carbon steel watertight piping close to the manhole facilities. This stretch of piping was completely replaced to the extent needed to bear material in good conditions.

    Afterwards, Extent of the cause was applied on all buried BONNA piping (on this system and also on the fire protection system). On other carbon steel piping outside buildings susceptible to corrosion due to seawater conditions inspections were performed such as many sample excavations, tests and studies. A hydraulic test was performed on all the BONNA systems.

    The same corrosion mechanism was found on the transitions of buried to aerial piping in the entrance to the

    building or outside.

  • 14

    The Incident & the System . Inmediate corrective actions

    General: The cathodic protection, although it has not been 100% efficient, has minimized internal corrosion (maximum localized loss measured of 0.85 mm which is 10 times higher than the generalized corrosion). Therefore the main problem in Vandells II is external corrosion despite it can be caused in some cases by welding defects.

    Zone 1 Boxes: The most affected zone due to external seawater conditions. All this zone is replaced during the refueling.

    Zone 2.1 Buried pipe except unions: Very small degradation observed. Good soil and concrete protection. Calculations show that pipe can support design loads with a complete loss equivalent to a hole of 60 cm in diameter of liner and rebar.

    Zone 2.2 Buried pipe unions: As there are no reinforcing bars in this zone, such is the most critical part. Generalized corrosion of a maximum of 1mm and local corrosion between 2 to 3.5 mm has also been observed in this zone. Calculations show that these unions can support design loads with a generalized loss up to 1.5 mm remaining, and a local loss up to 2mm remaining in an area of 400 mm2.

    Hydro tests: It was analyzed that a hole of 0.5 mm diameter in the unions would result in a leak of 17 l/h during a 6 bar pressure hydro test. The maximum values measured during test were 2.1 l/h.

    Main insights from the analysis performed by ANAV with the suppoMain insights from the analysis performed by ANAV with the support rt of IET, CIEMAT, OXAND and IDOM:of IET, CIEMAT, OXAND and IDOM:

  • 15

    The Incident & the System . Inmediate corrective actions

    Main Conclusions:Main Conclusions:

    After the repairs and hydro tests performed: there are sufficient safety margins to assure the structural integrity under all design transients.

    Considering the different hypothesis and analysis performed: the current system can operate conservatively during a period of more than 5 years.

    A hydro test will be performed every refueling until the replacement of the current system.

  • 16

    The Incident & the System . Main projects to upgrade the system

    Addition of a new ESW safety class system that will add diversity with respect to the final heat sink (Forced circulation cooling towers) in two cycles.

    Independent cooling systems for Diesel Generators and Chilled Water System through the addition of an air cooler specific for each system.

    Replacement of all fire protection system - buried pipe also in the next two cycles.

    As future important physical actions identified in the As future important physical actions identified in the Action Plan to improve Safety Management Action Plan to improve Safety Management committed with CSN are:committed with CSN are:

  • Safety ManagementSafety Management

  • 18

    Safety Management . Events analysis

    Details on the sequence of events and on the root causes resulting from the internal root cause analysis performed by ANAV and the MORT (Management Oversight Risk Tree) analysis performed by an IAEA team with support from Conger&Elsea can be found in:

    EAR PAR 05-039 posted June 29 2005 on the WANO web.

    Thus the rest of the presentation will focus on ANAV Management insights and on the Action Plan to improve Safety Management accepted by the CSN (Spanish Regulatory Body).

    Note: In Spain the CSN is applying the SISC based on the NRCs ROP (reactor Oversight Process). Thus regulator actions are in accordance with those taken at a U.S. plant with a red category in one cornerstone.

  • 19

    Safety Management . External independent evaluation

    Group 1: Independent analysis of all aspects before and after the incident.

    Group 2: Nuclear Safety oversight mechanisms.

    Group 3: Evaluation of other recent events to evaluate common causes.

    Group 4: Safety culture evaluation.

    Group 5: Relationship between the Regulatory Body and the Plant Operator.

    As a part of the analysis, ANAV and CSN agreed to create the As a part of the analysis, ANAV and CSN agreed to create the so called GAE (External Advisory Group) so called GAE (External Advisory Group) withwith 5 5 workingworkinggroupsgroups ::

  • 20

    Safety Management . ANAV Management diagnosis

    Main contributors identified by ANAV :Main contributors identified by ANAV :

    Deficiencies in some Safety culture attributes and conservative decision making focused on operation.

    Responsibilities were not fully defined and understood in some cases and sometimes there is a lack of accountability (the others have the problem). This along with some lack of ownership is perceived as an indicator of leadership deficiencies.

    Long and medium term planning, including resource allocation , needing improvements as well as clear and practical prioritization guidelines.

    Lack or not use of the internal operating experience learningmechanisms.

    Insufficient presence of the management in the field and deficiencies in the supervision both by the line and by the quality organization as well as the oversight mechanisms.

    Vertical and horizontal internal Communication deficiencies as well as externally with the CSN. This deficiency is considered to have caused a deterioration in the relationship between both organizations.

  • 21

    Safety Management . Action Plan

    As a result of all previous work done, the recommendations from these groups and a WANO Corporate Review, a final

    Action Plan to improve Safety Management Action Plan to improve Safety Management

    was agreed and committed with the CSN.

    This plan is currently in revision 3.

  • 22

    Action Plan to