Managing of the damaged fuel at
Paks NPP

Larisza Szőke
head of nuclear fuel section,
deputy project leader (encapsulated fuel management project)
1st International Forum on the Decommissioning of the Fukushima Daiichi Nuclear Power Station
11 April 20161

General information (Hungary, Paks NPP)
Location: Central Europe
Area: 93 000 square
kilometers
Population: less than 10million

4 VVER-440 type Units;
Commissioning time:
1982-1987
Original design:
1375 MW, 440 MWe,
After power uprate project1435 MW, 500 MWe2000 MW,  50% of domestic production
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Cause of the accident•In 2002 the Units 1-3 were operated at lower power (the coolant flow rate had decreased due
to magnetite deposits on the fuel assemblies (FA).
•Paks NPP made the decision to clean up the FAs from the deposits during an annual outage.
•In April 2003 in course of cleaning of the fuel assemblies in a specially designed andmanufactured cleaning tank, located in pit No. 1 of Unit 2 of Paks NPP, violation of thecooling regime took place with consequence of damage of the fuel assemblies

On April 11, 2003
cooling problems
during cleaning up
a batch of 30
irradiated fuelassemblies caused
an incident,damage of 30 fuelassemblies.

3pit

pool
reactorcleaningtank &damaged
fuelFirst phase of the liquidation of consequences of theincident

In Paks NPP’s case the full recovery of theconsequences of the incident took more than 11 years.
The purposes of the first phase were:to investigate the cause of the accident and to understand the conditions of the fueland the pit (4 weeks),
to stabilize the fuel and to ensure the safe conditions of damaged fuel and theUnits (4 months),
to establish the project responsible for recovery (2 months).
The works were implemented mostly by NPP's specialists andthe domestic Research Institutes and Design Organizations∑ mass SF  6 t
UO2  3,5 tons
U-235  70 kg)
Pu  20 kg
only damaged,not molten)
2003
4

2007

2013

201
4

Communication
Proactive, open and systematic communication with the publicboth at the local and national levels.
Goals:•to achieve the public understanding of the situation,•to provide true information and to enhance a trust of local people,•to explain the possible management of damaged fuel in safe manner.

The 1st press release on the day of incident. 04.22 .2003-the first press releasefrom the reactor hall; after stabilization of situation (in May) every day press
release with new information. From July till November weekly press-release. Big
international conference on the spot after the removal of fuel from cleaning tank.

5Second phase of the liquidation of consequences ofthe incident
The purposes of the 2nd phase were:preparation of the fuel removal (developing of technology, design of equipment
and tools), licensing,fuel removal.

Main facts:• In 2003 the power plant and Hungary were not in possession of suitable
technology, and had not enough experience for liquidation of the incident
consequences.
• The works had to be performed in environment of power plant in operation.
In 2003 OAO “TVEL” and Paks NPP entered into a contract, in accordancewith which Russian specialist, in compliance with all requirements of nuclear
and radiation safety had to elaborate technology for removal of the damaged
fuel assemblies from the cleaning tank,
emptying pit No. 1, as well as to performthe practical works.
For solution of the tasks in Russia
a team has been established underleadership of OAO “TVEL” including
leading companies of the industry.
6Canisters & casks+7

Main recovery equipment, tools
24.7 t13.9 m>80 different
kind of tools•Fixing,•Drilling,•Cutting,•Catching,•Suction,•Washing,•Lifting.
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Fuel removal operations• Technology characteristics:– Loading of the fuel under water by remotely, pneu/hand-operated tools ,– FA without head/leg into vented canisters,– fuel rods and debris into space holders and canisters,– head/leg into SRW cask,– underwater weighing (safeguards, filling limits).
Clear out the upper plate of the tank from SFA and fuel rod fragments.
Separate the SFA end parts from fuel columns and load theminto SRW vessels• Direction of fuel removal:

Clear out the fuel rod fragments from the middle of the tank

Cut the upper plate into fragments.
Remove the SFA fragments from under the plate

Remove the bulk SNF and SFA fragments from the lower plate

Drill through and remove the central part of the lower plate

Remove the bulk SNF and SFA fragments from the bottom of the tank

Preparation time

Fuel loading into canisters
2003
92006

2007

2013

201
4

Control panel & displays
platform in the pit

refuelingmachine

control panel

display10

Upper view of the platformhorizontal saw
display

working slot
Lead glass
window

display
alarm unit
11

crane control

Storage of canisters in the spent fuel pool„Wet” storage = „Ventilating compensator”
24 pcs. ofcanisters, type
28 (big)pit

8 SRW casks
1244 pcs. of canisters, type 29 (small)Third phase of the liquidation of consequences of the incident

Objective: to restore the conditions of the plant prior tothe incident!
Main steps:• elaboration and substantiation of the technology of drying and hermetical sealing of thecanisters, licensing,• substantiation of the transportation, licensing,• drying out of canisters and transportation of all canisters to a reprocessing facility.
Requirements to the technology:•to optimize the needed resources,•to minimize the quantity of waste, activity release and radiation exposure of the personnel andpopulation,•the works should not disturb the normal operation of Units 1 and 2.

It was necessary to carry out the experiments studying the behaviour of damaged
nuclear fuel in canisters and verifying the feasibility of drying technology (theseexperiments have been carried out by Russian Research and Development company„Sosny” and Research Institute „NIIAR” in Russia).
On the base of research works the drying out of fuel and transportation of canisters toreprocessing facility in Russia became feasible (Hungary does not have reprocessing
factory, the existing Spent Fuel Interim Storage Facility is licensed only for normal
spent fuel).
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TECHOLOGY used fordrying and hermetical sealing the canisters

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In second half of 2013 all 68 capsules containing the spent fuelwere successfully dried out.

Shipment of the SF to the reprocessing facility
In summer 2014 the capsules were successfully shipped to Russia to “Mayak”.
By this the project for full recovery of the consequences of the accident of 2003
was successfully completed.

SF removalfrom thecleaningtank

Post accident
stabilizing time

1. Phase

2. Phase
Preparatiom for SF removal fromthe cleaning tank

2003
15

2006

Development of drying technology

2007

Storagebefore shipping
Drying,sealing

3. Phase

Shipping

Design and manufacturing ofequipment

2013

2014

Main clues of the success (1) Collection , analysis and utilization the information from around the world,
 Establishment of responsible project organization, permanent support from amanagement of NPP.
 The safety (nuclear, personnel protection, operational safety) had the highestpriority.
 Enough time for all preparing works (no tight schedule) (in our case 11years!).
 For solution of tasks the leading (design, research, engineering,manufacturers) companies of the industry were involved in Russia and inHungary.
 Conservative approach in all works.
 All significant analyses were performed at least in 2 independent
organizations, the results were compared and evaluated.
 Mock –up tests on all phases.
 Before implementation all equipment and technology were tested in place offabrication and in real (but inactive) conditions at site.
 Only well trained personnel after additional examinations were involved inworks.
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Main clues of the success (2) Each step of works was licensed by Hungarian Atomic Energy Authority. All
requirements of National Nuclear Rues and IAEA Safety Standards weretaken into consideration.
 Almost in all phases of recovery the Hungarian Atomic Energy Authority
created additional strict criteria.
 All works were implemented with permanent consultation with Authority andunder supervision of Authority.
 RU/US regulatory evaluation of the developed technology for the fuel removal(by HAEA NSD request).

ГАНФЕДЕРАЛЬНОЕ ГОСУДАРСТВЕННОЕУНИТАРНОЕ ПРЕДПРИЯТИЕВО «БЕЗОПАСНОСТЬ»ГОСАТОМНАДЗОРА РОССИИЭКСПЕРТНОЕ ЗАКЛЮЧЕНИЕна отчет Федерального ГосударственногоУнитарного Предприятия (ФГУП) “Гидропресс”«Разработка технологии выполнения работ”(У213-Пр-1764) по теме “Ликвидацияпоследствий разрушения кассет в колодце №1
на блоке 2 АЭС “Пакш”».
06.0001.01.00010.04

US NRC

Regulatory Observations for
Recovery of Damaged Fuel
Presented by George Kalman and Mikey Brady Raap
Pacific Northwest National Laboratory
USNRC-HAEA Consultation, Budapest, Hungary
April 19-21, 2004
117

Thank you for yourattention!

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