Ali Asghar

Pakistan Atomic Energy Commission

IAEA Technical Meeting on Integrated Approaches to the Back End of the Fuel Cycle Headquarters Vienna Austria, 17–19 July 2018

The Back End: Spent Nuclear Fuel Management in Pakistan

Outline

• PAEC Nuclear Power Program

• Overview of Strategy for SFM in Pakistan

• Back End Policy and Strategy

• Interfaces Issues in SFM

• Stakeholders Responsibilities

• CHASHNUPP, Spent Fuel Management

• KANUPP, Spent Fuel Management

• Conclusion 2

CHASNUPP KANUPP

C-1 C-2 C-3 C-4 K-1 K-2/K-3

Commercial

Operation2000 2011 2016 2017 1972 2021

Rated Thermal

Power MWth998.6 998.6 998.6 998.6 432.8

Gross Electric

Power MWe325 330 340 340 137

1100 MW

each

Reactor Type PWR PWR PWR PWR PHWR PWR

Origin China China China China Canada China

3

Pakistan’s Nuclear Power Program

• To have significant portion of nuclear energy in the overall

energy mix. It is central element of Pakistan's energy policy.

• Following strategies are adopted for SFM:

– Enhancement in Capacity of Wet Storage Pools.

– Facility Development of Spent Fuel Dry Storage.

– Site Selection for Ultimate Disposal Facility

– Hold and See Strategy.

4

Overview of Strategy for SFM in Pakistan

5

SNF from Reactor Core

On-site Wet Storage On-site Dry Storage

Closed cycleDeep Geological

Repository

Back End Policy and Strategy

Policy? Policy?

• Issues in implementing of re-racking strategy in wet

storage to enhance the storage capacity beyond design.

• Need to develop improved strategy for Integration of Wet

SNF storage & Dry storage at Reactor Site

• Design & Manufacturing of transportation & storage Casks

• Licensing interface among PNRA,PAEC and IAEA for dry

storage facility and Casks

6

Interfaces Issues in SFM

Responsibilities of Operators (PAEC)

• In Pakistan, PAEC, the main operator, is responsible for

Safe Management of Spent Fuel

• As per policy, a Central Radioactive Waste Management

Fund is maintained by PAEC.

• SNF is currently stored (Wet) at the reactor sites in pools.

• Longer-term dry storage at each site is proposed and

work is in progress. 7

Responsibilities of Stakeholders for Spent Fuel Management

Responsibilities of Regulator (PNRA) :

• Responsible for development of requirements and

procedures for the licensing of various types of

radioactive waste management facilities.

• Responsible to advise and inform on technical matters

and on the effect of polices with respect to assuring the

safety of the public and the environment.

8

Responsibilities of Stakeholders for Spent Fuel Management

Responsibilities of Directorate General National

Repository (DGNR)

• Responsible for Disposal Activities: Off site

transportation, Siting and development of disposal

facilities

9

Responsibilities of Stakeholders for Spent Fuel Management

10

Main NPPs sites

CHASNUPPWet Interim Storage

(in-operation)

Dry Interim Storage(under construction)

KANUPPWet Interim Storage

(in-operation)

Dry Interim Storage(under construction)

11

CHASHNUPP(C-1 to C-4)

Plant Storage capacity

Occupied Remaining space

Adequacy(year)

C1 721 FA* 440FA 321FA 2021

C2 721 FA 200FA 521FA 2030

C3 721 FA 40FA 681FA -

C4 721 FA - 721FA -

Storage capacity: SNF generated from15 RFOs (600 FA)+ 1 full core (121 FA)=721

*FA: Fuel Assembly

12

Spent Nuclear Fuel (SNF) Storage at Reactor Pools by JUNE, 2018

• Overall length, mm:

– 3500

• Overall transverse dimensions, mm:

– 199.3 × 199.3

• Mass of assembly, kg:

– 462.54

13

Fuel Assembly Characteristics

STORAGE POOL 2

Cask Loading Pool4x4

Cask Cleaning Pit

4x4

Cask Handling Opening 5.4x3

TRANFER

CANAL

STORAGE POOL 1

14

Lay Out of Fuel Building Wet Storage

15

75t

12.150

Pool Crane 2/5t

13.300

1.7501.500

8.000

±0.000

5.150

10.500

16.800

22.400

25.000

20.000

SPENT FUEL STORAGE POOLCaskLoadingPool

CaskCleaningPit

4.8

Spent Fuel Building

15

16

Spent Fuel Storage at CHASHNUPP

• PAEC has planned to establish Dry Storage facility which

will serve as interim storage for spent fuel till availability

of National Repository (Hold-n-See).

• Location: within plant boundaries

17

Long Term Strategy for SNF Storage (Dry Storage)

• Scheme:

– Canister (including basket)

– One Metallic Cask (Transfer Cask)

– Single purpose Concrete Casks (dry storage)

– Storage building with hot cell

• The dry cask storage system will provide confinement,

radiation shielding, structural integrity, criticality control and

heat removal for SNF. 18

Dry Storage Scheme (Proposed)

▪ Due to harsh environmental conditions and security issues

indoor storage of dry casks on concrete floor is selected.

▪ Three buildings with passive ventilation features will be

constructed.

▪ The storage capacity of three buildings will be sufficient

enough to store SNF generated from 60 years operation

of C1 ~ C4.

19

Dry Casks Storage Buildings

• For Site Specific license of dry storage facility CNPGS will follow

US NRC 10CFR 72

• For licensing process, PNRA regulation “Regulations for Licensing

of Nuclear Installations in Pakistan, PAK/909 (Rev.1)” will be

followed

• Letter of intent and information regarding license applicant

forwarded to PNRA

• PAEC, Disarmament & Safeguard directorate has forwarded the

CNPGS intent to IAEA for provision of safeguards measures 20

Licensing Issues

21

KANUPP

• The KANUPP SFB is divided into four areas.

– Storage area

– Inspection area

– Shipping cask area

– Decontamination area

• Designed for 20 years of operation with 80% capacity factor

22

KANUPP Spent Fuel Bay

23

Spent Fuel Bay at KANUPP

• 11 spent fuel bundles stored in one storage tray

• Storage Layout : 120 stacks of trays each 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) above the

water surface 24

KANUPP Spent Fuel Bay (SFB)

• Almost complete its design capacity

• An alternate short term remedy is to enhance the storage

capacity of existing SFB

• A dry storage facility is being planned as an ultimate

solution of storage problem

25

Storage Problem in SFB of KANUPP

• Increase in no. of layers / stack.

• Place cooler bundle tray at top of stack.

• Reserve space for storage of in-core fuel bundles in

emergency conditions.

26

Enhancement in Storage Capacity

• Computation of thickness of water column for shielding

• Analysis of cooling capacity of bay water

• Criticality assessment (requirement of the regulator)

• Seismic Analysis

27

Addressing Issues for Enhancing Wet Storage Capacity

– Contribution of all spent fuel bundles stored in storage bay is

modeled

– The rate of decrease of activity & decay heat of spent fuel is

very fast within 10 years of cooling time; slows down after

wards

– 10 years cooling period is considered in the shielding

Calculations

28

Water Shielding Thickness Calculation - Assumptions

Water Shielding Thickness Calculation for Cooling Period of 100 Years at Different

Burnups

1.0E+11

1.0E+12

1.0E+13

1.0E+14

1.0E+15

1.0E+16

1.0E+17

0 10 20 30 40 50 60 70 80 90 100

Ph

oto

ns

/ se

c

Cooling Time (Year)

3000 6000 9000 12500

29

• 2.13m water column thickness is sufficient to maintain

required dose rate ~ 8.7E-3 mSv/hr

• The active height of stack with 24 fuel trays is about 2.44 m

• 3.51 m water column is still available to shield the spent fuel

• The dose rate with 3.51m water column comes out as 2.8E-6

mSv/hr

30

Water Shielding Thickness Calculation - Results

Dose rates due to 10 years, 5 years and 1 year cooled spent fuel

bundles are tabulated as:

Dose Rates (mSv/hr) w.r.t. various cooling periods at available shield thickness

Cooling Period (Years)

Dose Rates (mSv/hr)

Available Water Shield Thickness (m)

At 3.51 m At 3.20 m

10 2.78E-06 4.35E-06

5 6.09E-05 7.22E-05

1 1.22E-03 1.48E-0331

Dose Rates

• Design total heat removal capacity of bay cooling system is

1.8 MWth

• 0.21 MWth decay heat will be generated in the spent fuel

storage bay due to overall 31680 spent fuel

• 0.27 MWth decay heat is calculated due to unloading of in-

core fuel bundles (assuming 3 months cooling)

• The calculated total decay heat 0.48 MWth is well in limits

of design heat removal capacity of bay cooling system 32

Analysis of Bay Cooling Capacity

• The spent fuel placed in HDTR in proposed layout in the

spent fuel storage bay will remain subcritical in operational

and accidental conditions

• Use of steel in spent fuel trays, racks and liner in the

surrounding walls of the bay make Keff even lesser

33

Criticality Assessment

• A seismic analysis enabled to assess the stability against

seismic event (ground acceleration 0.2g)

• The result of analysis reveals that overturning will not take

place under the specified seismic loading

• Sliding will take place, however much less than the

clearance available b/w two adjacent racks or between a

rack and bay wall

• Stress analysis ensured that the axial, bending and shear

stresses are within the allowable limits34

Seismic Analysis

• Storage capacity of SFB enhanced by increasing tray stack

height from 18 layers to 24

• Seismic stability will be attained by placing these trays in a

“High Density Tray Rack”

– Two columns each consisting of 24 layers of trays will be loaded into

one rack

– 60 racks could be arranged in layout of 10 x 6 in the storage area of

SFB35

Improved Proposed Storage Pattern

• The high density tray rack is a seismically and structurally

qualified stainless steel

frame to be placed in storage

area of spent fuel storage bay.

36

Storage Capacity has been enhanced by 33.3%.

High Density Tray Rack

• Each rack will hold 528 spent fuel bundles

• 7920 more spent fuel can be stored

• Overall 31680 spent fuel can be accommodated

• The development and implementation of HDTR System at

KANUPP will enhance 1/3rd of design storage capacity

37

Proposed Amendment in Existing Storage Pattern

• High Density Spent Fuel (HDSF) racks are now successfully

designed, developed and manufactured.

• Total 06 racks are already lowered in the SFSB and additional 02

racks will be lowered in near future and this will provide storage

capacity for about one year.

• It is now planned to develop minimum 10 racks per year so that

maximum 60 will be completed that will be sufficient for plant

operation up to year 2019.

• SFSB capacity would be enhanced from 23,760 to 31,680

bundles after the installation of HDSF racks. 38

Proposed Amendment in Existing Storage Pattern

39

High Density Tray Rack (Loaded)

Parameters Existing StorageEnhanced 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 (11 x 18)528 (11 x 48)

Array in Bay 12x10 10x6

Number of Bundles in Bay 23760 (12 x 10 x 198) 31680 (10 x 6 x 528)

Fuel Storage Advantage (%) - 33.3

Available Water Shielding (cm) 396 351

40

Comparison b/w Existing and Enhanced Storage Scheme

41

High Density Tray Rack (In Storage Pool)

▪ Pakistan is committed to operate NPPs in safe & secure manner to fulfill the energy needs under IAEA assistance & safeguards

▪ Pakistan gives importance to back end activities of Nuclear Fuel Cycle

• Currently, following steps are taken in SNF Management atCHASHNUPP and KANUPP :– Enhancement in Capacity of Wet Storage Pools– Facility Development of Spent Fuel Dry Storage– Design and development of casks

▪ Initiation of siting process for Deep Geological Disposal Facility

▪ Wait and see Strategy for SNF 42

Conclusion

Thank you for your

Attention

43