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REPUBLIC OF SLOVENIA MINISTRY OF THE ENVIRONMENT AND SPATIAL PLANNING SLOVENIAN NUCLEAR SAFETY ADMINISTRATION

Post-Fukushima Safety Actions in Slovenia

Siniša Cimeša Slovenian Nuclear Safety Administration

MINISTRY OF THE ENVIRONMENT AND SPATIAL PLANNING SLOVENIAN NUCLEAR SAFETY ADMINISTRATION www.ursjv.gov.si

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Content

• Introduction

• Post-Fukushima improvements – Mobile equipment

– Stress tests‘ improvements

– Safety Upgrade Program, SUP

• Legislation changes

• Lessons learned and Challenges


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Introduction – Krško NPP

• Westinghouse PWR, 2 loop, 700 MWe

• At least 2x100% redundancy of safety systems

• Commercial operation since 1983

• Important facts: – Seismic design 0.3 g – Detailed SPSA done in ‘90s and

again in 2004 – Detailed flood protection analysis – SAMGs developed in late ‘90s – Full scope simulator in 2000

– Wet cavity modification


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Introduction – SNSA

• SNSA is an independent agency within the framework of Ministry of the Environment and Spatial Planning

• Reports directly to the minister

• It is financed solely by the state budget

• Legislation in line with WENRA

• Relying on US NRC‘s regulation and standards


Post-Fukushima improvements in the Krško NPP


Design Extension Conditions for Krško NPP

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Design basis

• Seismic: 0.3 g PGA • Flood: PMF = 7081 m3/s • Single failure criteria

• Station Black Out (SBO): 4 h • UHS: loss of river flow up to 30

days

• Loss of MCR temporarily – establish „hot shutdown“

DEC

• Seismic: 0.6 g PGA • Flood: PMF + earthquake (0.6g) • Assume loss of all trains of safety

systems • SBO: 72 h • UHS: loss of primary UHS for 30

days + combination with SBO for 72 h

• Loss of MCR indefinitely – establish „cold shutdown“

• Aircraft crash • Tornado (240 km/h) • Extreme temperatures (10,000

year return period)


Improvements in the Krško NPP

• Phase 1: – Mobile equipment and quick connection points (incl. procedure

changes) acquired and established before June 30 2011

• Phase 2: – Additional mobile equipment and connection points after EU

stress tests

• Phase 3: – Krško NPP Safety Upgrade Program

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Improvements: phase 1

• Mobile equipment and quick connection points (incl. procedure changes) acquired and established before June 30 2011 – Implementation of US NRC B.5.b action plan (following 9/11

event) – Credited in stress tests


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Fire truck with a hydraulic fire-fighting arm Tanks: 8500 l of water & 1500 l of fire-extinguishing foam



• As a result of stress tests several other improvements were identified, mostly acquiring additional pieces of mobile equipment – Finished by the end of 2012



Improvements: phase 1 & 2

• Mobile equipment stored in a shelter – Protected against external hazards (DEC): earthquakes, floods,

extreme weather, aircraft crashes…

• Quick connection points established

• Support equipment: – Resources (diesel, petrol, water) – Fuel transfer pumps – Connection cables – Fire hoses – Transfer trucks / tractors

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Improvements: phase 1 & 2

• Procedures – EOPs, SAMGs

• Testing & maintenance – Interval – Procedures (who, how and when)

• Training – Training operators/staff to use equipment

• Exercises with real scenarios – Checking feasibility (human and equipment resources) – Procedures validation



• In September 2011 SNSA issued a decision requiring from the plant to reassess the SAM strategy, and existing measures and to implement necessary safety improvements for prevention of SA and mitigation of its consequences,

• This evaluation concluded in January 2012

• Action plan, so called „Krško NPP Safety Upgrade Program“ (SUP)

• Endorsed by SNSA in February 2012


Phase 1 completed

in 2013

Phase 2 underway

– to be completed

by 2018


• The Krško NPP‘ SUP improvements: – Replacement of active hydrogen recombiners with passive ones

(PARs) – Installation of (passive) containment filtered vent system (CFVS) – Flood protection of the nuclear island – Operation support center reconstruction – Installation of pressurizer PORV bypass – Spent fuel pool (SFP) alternative cooling – Alternate cooling of reactor coolant system and containment – Installation of emergency control room (ECR) – Upgrade of bunkered building #1 (BB1) electrical power supply – ECR / Technical support center ventilation and habitability system – Replacement and upgrade of critical instrumentation


Phase 3 to be

completed by 2021


• The Krško NPP‘ SUP improvements: – BB2 Project – independent injection / cooling system in a bunkered

building with additional sources of borated and unborated water with dedicated pumps for injection into reactor cooling system / containment and steam generators capable of assuring reactor cooling for at least 30 days.

– Erection of dry spent fuel storage facility

– All these improvements (SUP) will be designed for Design Extension Conditions – DEC !!


– Passive recombiners (PARs) – Containment Filtered Vent System (CFVS)

SUP – phase 1


• Flood protection of the nuclear island – implemented in 2015-16 – Flood protection doors, temporary flood barriers, replacement of

flood protection check valves, penetration seals improved – Protection of the Krško NPP in case of combined maximum flood

and (design extension) earthquake

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SUP – phase 2, underway


Changes in Legislation

• Alignment with the amended EU Nuclear Safety Directive (Law, Rules JV5 and JV9)

• Alignment with the EU Basic safety standards directive (BSS)

• New Rules JV5 and JV9 – WENRA Safety Reference Levels of 2014 – WENRA Safety Objectives for new reactors, 2013


Lessons learned

• Importance of Periodic Safety Review (PSR) • Ongoing plant improvements started before Fukushima

accident – 3rd full scope EDG (in bunkered building #1):

resulted from 1st PSR, under construction during Fukushima accident, functional since June

2012

– Increased level of dikes on the left side of Sava river: resulted from 1st PSR, new, increased PMF, March 2012

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Challenges

• Timely implementation of the SUP improvements – Problems with public procurement – unsuccessful bidders‘ appeals

cause big delays in project implementations

• Upgrade of I&C – qualification for severe accidents

• Challenges with newly installed equipment – PARs – CFVS

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Expert feedback on the draft document

• … still in review…

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