SPENT FUEL STORAGE MANAGEMENT IN INDONESIA. SUMARBAGIONO Radioactive Waste Technology Center, Indonesian National Nuclear Energy Agency (BATAN)

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1 SPENT FUEL STORAGE MANAGEMENT IN INDONESIA SUMARBAGIONO Radioactive Waste Technology Center, Indonesian National Nuclear Energy Agency (BATAN)

2 INTRODUCTION There is only one ISFSF in Indonesia to store spent fuel from GA SiwabessyMulti-Purpose Reactor (GAS-MPR, 30 MW) operated since 1987 Spent fuel from GAS-MPR are kept in the reactor service pool for several months to allow a significant decrease in radiation level and decay heat production, before they are transferred to the ISFSF Some of the spent fuels are repatriated to the origin country, but most of them will remain stored in the pond for a long time until they are moved to dry storage or disposal facility The main problem is corrosion in the spent fuel and SSC of the ISFSF

3 FUEL TYPE Dimension (mm x mm x mm) 77.1 x 81 x 600 Clad Material AlMg 2 Clad thickness (mm) 0.38 Meat dimension (mm x mm x mm) 0.54 x x 600 Meat material U 2 Si 3 Al U-235 Enrichment (w/o) 19.75% Uranium Density (g/cm3) 2.96 U-235 weight per Fuel Element (g) 250 U-235 weight per Control Element (g) 178.6

4 ISFSF LAY OUT Pond : 14 m length, 5 m width, 7.6 m depth

5 ISFSF Profile Designed by AEA Technology, UK Operated since 1998 Multi barrier construction: SS-304 liner, pond walls, mild steel, concrete. Capacity: 1458 spent fuels SF store at SS rack

6 Fuel Transfer ISFSF OPERATION SF is transferred through a watery transfer channel (6.6 m underground) connecting the GAS-MPR to the ISFSF SF is transferred one by one to storage rack using a Mast Transfer Unit (MTU) 24 SFs per year discharged from the GAS-MPR. Until June 2013, there are 245 spent fuels in the pond SF transfer is also performed in repatriation program. 200 SFs had been returned to the USA in 1999, 2004 and 2009.

7 OPERATIONAL LIMITS ISFSF operation aims to ensure the safety of the ISFSF and to maintain the integrity of spent fuel and SSC of the ISFSF. The systems are operated with written standard operating procedures (SOP) that are designed and reviewed to ensure that the operation can meet the operational limits : Parameter Value ph Conductivity Pond water level Pondwater temperature < 15 µs/cm 6.5 m < 35 o C Aircontamination < 70 Bq/m 3 Roomtemperature Dose rate < 30 o C < msv/h

8 MAIN SYSTEMS OFTHE ISFSF System Purpose Water treatment system Demineralized water unit Pond cooling system Ventilation system Fuel transfer system Make-up water system Radiation monitoring system Treatment of the pond and the transfer channel water to maintain its chemistry, its clarity, and the radioactive content at acceptable levels. To replace water lost through evaporation under normal conditions. To wash the resin beds when they need replacing. Removal of heat arising in the pond from the spent fuel and maintain the water at 35 o C by chilled water. To provide a satisfactory working environment for the operators. To minimize the spread of any air-borne contamination, and in particular its release to the environment. To transfer spent fuel from reactor to ISFSF and to handle the spent fuel at the ISFSF building. To supply pond water to compensate for water loss by evaporation or leakage. To measure radiation dose rates and airborne radionuclides. Continuously operated with local alarm and unambiguous readouts. To detect contamination on workers.

9 MAINTENANCE Maintenance program is established for controlling maintenance, inspection and testing of the ISFSF SSCs Maintenance using preventive maintenance approach conducted periodically by licensed officers to retain the condition of the SSC and prevent failure through the prevention of deterioration, periodic inspection, condition diagnosis, testing, and replacing parts to prevent problems. It also includes daily cleaning, inspection, lubrication and tightening.

10 AGING MANAGEMENT Aging degrade the SSC performance need an aging management Aging management is an obligation in accordance with Indonesian Nuclear Energy Regulatory Agency Chairman Decree Number 7/2012. Pre-implementation assessment study has been conducted to assess implementation of aging management on the ISFSF The study cover implementation stages of aging management, i.e. screening to determine critical SSCs, evaluation of the aging effects on critical SSCs, preventive of aging effects, surveillance and mitigation of critical SSCs. The study concluded that the SS liner of the pond s wall is a critical SSC Aging effects prevention can be done by maintaining the quality of the pond water, and adding an inhibitor. Surveillance can be conducted visually using underwater camera and coupons If leakage found then SF is temporarily moved to the transfer channel, installing insulation between the channel and the pond, draining and drying the pond, maintaining water in the channel and repairing the critical SSC by welding or material replacements.

11 SF CORROSION Aluminiumclad nuclear fuel is subject to corrosion attack if the water quality and storage conditions are aggressive to aluminium. Primary forms of corrosion: pitting corrosion, crevice corrosion, and galvanic corrosion. The major factors: conductivity, ph, and bicarbonate, chloride, sulphateand oxygen content. The effective control of the pond water quality is the most important thing to control corrosion. aluminiumclad alloys can be stored with little or no corrosion in ponds water with conductivity 1 3 µs/cm

12 CONDUCTIVITY LEVELS OF POND WATER AT THE ISFSF AROUND THE U.S.A ISFSF Brookhaven National Laboratory Water conductivity about 0.5 µs/cm no evidence of cladding breaches Oak Ridge National Laboratory µs/cm no evidence of corrosionin 8 years Georgia Institute of Technology 1 µs/cm or better Receiving Basin for Off-Site Fuel (RBOF) facility at Savannah River Site(SRS) no corrosionproblem for over 25 years 1 3 µs/cm not experiencing corrosion problems Idaho Technologies CPP-666 basin Westinghouse Hanford Company K-East basin Westinghouse Hanford Company K-West basin 1 2 µs/cm no corrosion problem 3 5 µs/cm no corrosion problem 1 2 µs/cm no corrosion problem

13 CORROSION SURVEILLANCE The corrosion surveillance program has been conducted using test coupons immersed into the spent fuel storage in vertical and horizontal position (conductivity: us/cm, ph: ) The corrosion that might occur are crevice and galvanic corrosion and no pitting corrosion was found.

14 GALVANIC CORROSION ISSUE Use of SS racks could accelerate the galvanic corrosion of the aluminiumclad fuel To reduce the corrosion: an insulator spacer made of ceramic material to isolate contact between the rack and the spent fuel. However, it is better if the whole racks replaced with aluminium racks.

15 CONCLUSION Spent fuels will be stored for decades in the ISFSF s pond, so the management should be able to maintain their integrity during their stay in the water environment. The main issue on the wet type ISFSF is corrosion as it could damage the spent fuel and degrade the performance of the SSC. Crevice corrosion and galvanic corrosion are most likely to occur in the ISFSF. The operation and maintenance should be able to control the quality of water in the pond according to the requirements for corrosion prevention. To prevent galvanic corrosion of the aluminiumclad fuel, the SS rack should be replaced with aluminum rack or install insulator spacer to cut off the contact between the two different materials.