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By

Sohail Ejaz Abbasi and Arif Habib

Karachi Nuclear Power Plant (KANUPP)

Pakistan Atomic Energy Commission (PAEC)

CANDU Reactor In operation since 1972 Under water storage of spent fuel bundles in spent fuel

storage bay Completed 30 years design life in the year 2002 By refurbishment & safety upgrades, KANUPP

operational life extended up to 2021

432.8 MWth, 137 Mwe 208 Horizontal Fuel Channels

11 fuel bundles per channel

Weight of U/bundle = 13.4 Kg

Average Core Burnup = 3700 MWD/TeU

Average Discharge Burn-up = 7400 MWD/TeU

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11 spent fuel bundles stored in one storage tray

Storage Layout (Original Design): 120 stacks of trayseach consisting of 18 tiers of trays

Design Storage capacity: 23,760 spent fuel bundles

Total Water Depth : 5.94 m

Water Shield thickness: 3.96 m

8.7E-3 mSv/hr is maintained at 30.5 cm (1 foot) abovethe water surface

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Almost complete its design capacity June 2010

A dry storage facility was planned as an ultimatesolution of storage problem

An alternate short term remedy was to enhance thestorage capacity of existing SFB

Computation of Thickness of water column forShielding

Analysis of Cooling capacity of bay water

Criticality Assessment

Seismic Analysis

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Storage capacity of SFB enhanced by increasingtray stack height from 18 layers to 24

Seismic stability attained by placing these traysin a High Density Tray Rack (HDTR)

Each rack hold 528 spent fuel bundles

The development and implementation ofHDTR System at KANUPP has enhanced 1/3rd

of design storage capacity

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Parameters Design Storage Enhanced Storage

(HDTR System)

Single Storage Unit in Bay 18 Fuel Trays Stack 48 Fuel Trays Rack

(2 x 24 trays)

Number of Bundles in Single

Unit

198 528

Array in Bay 12x10 10x6

Number of Bundles in Bay 23760 31680

Fuel Storage Advantage (%) - 33.3

Available Water Shielding (cm) 396 351

Seismic Qualification (0.2 Ground

Acceleration)

Not Qualified Qualified

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Old Storage Pattern

Current Storage Pattern

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To achieve ultimate solution for spent fuelstorage space problem in existing bay, aninterim spent fuel dry storage facility has beenconstructed within plant premises

Operation of HDTR has been stopped, as thedry fuel storage facility is in operation

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Storage Facility

Design capacity more than 36000 bundles (1972-2021)

Designed for up to 50 years

Stored ≥10 years cooled spent fuel bundles

Principal Function

Create space in spent fuel bay to accommodate freshly discharged bundles

during plant operation 2019-2021, Short Term Benefit

Provide alternative storage facility for entire inventory, so as to make plant as

green area during decommissioning, Long Term Benefit

Location of Facility

Located within plant boundary 250 m away from reactor in N-E direction

One building has been completed

Layout of Facility

Two separate identical buildings, surrounded by security fence

Each building (83m x 23m) would house 168 concrete casks

Each building has 30 ton overhead crane for handling of storage casks

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System Purpose

To safely handle and store the ≥10 years cooled spent fuel bundles in dual

purpose concrete cask

To contain the spent fuel sheltered in concrete cask for a period of 50 years

Basket Preparation

Spent fuel bundles loaded into basket from fuel tray after tilting them vertical

Inspection area in spent fuel bay is used for this activity

Cask Preparation

Basket loaded into concrete cask under water

After draining and decontamination, top lid welded with cask body

Sealing of cask is performed at service building

Transportation

Concrete cask transported from service building to KSFDS facility by Low Bed

Trailer

Cask Storage

Finally cask stored at concrete Pad in Storage building through overhead crane

This operation performed at KSFDS building

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Concrete Cask Cask contains 2 baskets with 108 bundles (≥10 years cooled)

550 mm thick reinforced barite concrete wall provided for shielding to limit surface dose rate up to 1.0 mSv

6 mm steel liner provided for containment

Filled cask weight about 18 ton

IAEA safeguards system incorporated

Fuel Basket Contains 54 bundles in vertical position

Consists of stainless Steel base subassembly and cover subassembly

Filled basket weight about 1.2 ton

Fuel Bundle Tilter Remote manual handling device used for changing the orientation of 11

horizontal fuel bundles to vertical

In Bay Work Tables Two tables placed on Inspection area of bay, Basket Table & Tilter Table

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Cask Handling Tool

York type tool designed to handle 18 ton cask

Designed to operate on single failure criterion

Cask Top Lid Handling Tool

A tool is designed to handle cask top lid independently from cask

Basket Handling Tool

Designed to handle basket base, empty basket (base + cover)

The same tool is used to handle loaded basket (1.2 ton)

Two separate tools required (under water & out side the water)

Basket Cover Handling Tool

During basket preparation operation, for loading the bundles into basket, cover

from basket base is required to remove by using basket cover handling tool

Vertical Bundle Handling Tool

For handling of spent fuel bundle from tilter in vertical position, a tool is

required

A long handle manual tool with high reliability to operate without bundle drop

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Transport Vehicle

Used to transfer concrete cask from service building to KSFDS facility (250m)

Consists of: Low-Bed Trailer & Standard Prim-mover.

Concrete cask along with Tiedown would be attached with transport vehicle

Facility Crane

Each building has 30 Ton overhead electrical operated crane

Standard crane to handle cask from transport vehicle to storage location

Welding Machine

To perform welding operation of cask top lid to cask body, a dedicated manual

welding machine is required

Make seal weld to provide cask containment

Weld test is performed by Ultrasonic Method (UT) / Penetration Test (PT)

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Structural Integrity

Cask and raft qualified against natural and man-made hazards

Heat Removal

Decay heat removal from 10 years cooled fuel made by passive means

Confinement / Containment

Seal weld b/w lid liner to the cask body liner forms a single confinement boundary

As cask has single barrier, It is designed and manufactured in accordance with

ASME Section III, Division 3 (Safety Class Component)

Inspection of Confinement / Containment

To verify the integrity of seal weld, periodic inspection would be performed by UT

Shielding

Thick reinforced barite concrete medium provided for shielding to limit 0.5mSv

Criticality Control

No issues of criticality in this system

Fuel Handling

All associated tools be qualified before putting them in operation 20

Basket Preparation

Cask Preparation

Transportation

Cask Storage

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Receive empty basket and place it

underwater on table

Remove basket cover & place it on the

same table

Pick one fuel tray and place it on the tilter

Tilt 11 bundles and load them into empty basket

Place basket cover on basket base

Verify the bundles ID Nos. & Dose rate

measurement

Repeat step #4 and step# 5 until basket full of 54 bundles

Remove empty tray from tilter and place a new one on tilter

Place loaded basket on temp. basket

storage area in SFSB

Repeat the cycle for storage of second

loaded basket

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Pick cask body & lower underwater

into SFSB

Place top lid on cask body & raise the

cask outside water

Pick 2nd basket from temp. storage area &

place it into cask

Decontaminate & drain the cask

Lift the cask & place it on welding station

Weld the top lid with cask body

Inspect the weld quality by UT

Receive empty cask from yard at service building by vehicle

Remove hatches (SH-2) b/w service building and SFSB

Pick cask top lid from cask & place it at

decont. area

Pick one basket from temp. storage area &

place it into cask

Place cask on shipping cask loading area

Install IAEA Safeguards SealsDrying storage cask

using CICS

Spent Fuel Measurement with CANDU Bundle Verifier (CBVB)

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Safeguard Seal

For restricting unauthorized access to fuel, Cask is designed to facilitate provision

of applying IAEA Electronic Optical & Cobra type seals

IAEA inspector would inspect seal integrity periodically

Dose Rate Verification / Measurement

One verification pipe provided in each concrete cask running inside the cask wall

Unique Gamma profile of stored basket for each cask can be re-verified by IAEA

inspector periodically

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Receive transport vehicle at service

building

Lift cask from welding station & place it on vehicle

Measure dose rate and apply

admin. controlMove towards KSFDS facility

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Receive transport vehicle at KSFDS facility

Lift the cask from vehicle & place it on foundation

pad Mark identification number on the cask

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Concrete Cask based Spent Fuel Dry Storage System has been

implemented for KANUPP spent fuel

Concrete cask technology is well proven worldwide at various NPPs

and would require less regulatory re-qualification

KSFDS System is designed on the basis of safety and implemented

safely

The regulator accord the in-principle approval of this basic

preliminary scheme design

Detailed scheme along with the detailed equipment / tool design

performed

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Design and Construction of KSFDS Building

Development of Underwater Tools and Equipment forspent fuel handling; Commissioned both in mock-upand SFB

Inspection of spent fuel bundles with underwaterradiation resistance camera for condition assessment

Development and Certification of Spent fuel storagecask (SC-108) by regulator (PNRA)

Development of cask handling tools

Installation of single-failure-proof cranes in ServiceBuilding and KSFDS facility building

First cask transfer activity was carried out from 19 to 29August 2019 in the presence of IAEA SafeguardsInspectors

Three casks have been transferred to KSFDS Building

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THANKS

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