CANDU TRF MUST-KNOW OPEX - Energy

LIFE CYCLE MANAGEMENT SOLUTIONS Proprietary & Confidential Copyright © 2016 Kinectrics Inc. All rights reserved.Page 1

GENERATING SUCCESS ─ FOR OVER 100 YEARS

CANDU TRF MUST-KNOW

OPEX

Stephen Strikwerda23-25Oct2018


Background

• Retention of knowledge and transfer of information is an industry issue due to staff retirement

• TRF operation important to improve worker dose and emissions for Ontario, Canada and Korean CANDU reactors


Must-Know OPEX• INPO Must-Know OPEX Review

– INPO Chemistry Must-Know OPEX, INPO 12-002• CANDU Must-Know OPEX Review

– COG Chemistry Must-Know OPEX, COG-JP-4567-01

• Follow-up COG-funded Must-Know OPEX reports:– D2O Handling Must-Know OPEX Review; COG-JP-

4572-NN– TRF Must-Know OPEX Review; COG-JP-4598-NN


CANDU Heavy Water Cycle

Upgrader

Moderator>99.8% isotopic

Heat Transport>98% isotopic

<1.2 Ci/kg

CANDU PLANTDowngraded Heavy Water Collection Systems/Clean-up

(HW Escape)

HW/T Losses

HW/T Losses

HW/T Losses HW Make-up

HW Transportation

HW Transportation

HW Detritiation

HW/T Losses

Tritiated Waste

Tritiated Waste

Tritium Storage


TRF Background - Process

TRANSFERCatalytic Exchange

LPCE

ENRICHMENTCryogenic Distillation

PACKAGINGMetal Hydride Storage

DTO + D2O

D2O

D2 + DT

D2

T2


TRF Auxiliary Systems

AuxiliaryServices

TRF Interface

Steam& CondensateInstrument AirCompressed AirBreathing AirChilled WaterService WaterFire WaterDomestic WaterDemineralized WaterLiquid NitrogenElectric Power (normal & standby)Sewage & DrainageMisc GasesRadioactive Waste Management

D2O Product Purification and Storage

D2O Feed Purification and Storage

D2O

D2O/DTO

LPCE(350K, 70°C)

D2O/DTO

D2O

D2/DT Purification(Mol Sieve Dryer, CATOX, Cryogenic Adsorber, Liq

ring compressors)

D2/DT Cryogenic Distillation(24K, -250°C)

D2

He Refrigerator

Low Tritium Expansion

Tank

High Tritium Expansion

Tank

Tritium Gas Handling System

Glove Box and Glove Box Clean-up system

T2

D2/DT

Tritium Storage

D2 Makeup System (Electrolysis)

D2

D2O

Liquid Collection System

From all D2O-containing systems

Purge Gas & Recombiner

O2

From all Subsystems

D2O For Upgrading or Detritiation

Air Clean up System HVAC

Building Exhaust

Downgraded D2O to Upgrading


Methodology• Did the event have a lasting effect; that is, did it

shape TRF performance?• Was the event severe or unusual?• Was the event a result of improper equipment

operation?• Did the event have a significant impact on plant

reliability?• Did the event result in major equipment damage?• Did the event or series of events lead to significant

economic loss?• Does it represent best / common station practices in

TRF operation?


Methodology

• 5 Buckets for Lessons Learned:– Throughput – Leaks– Hydrogen Handling– Cryogenics & Vacuum – TRF Programs & Practices


Methodology

• Review of DTRF’s Station Condition Record database

• Key OPEX sent by WTRF and DTRF• WTRF and DTRF OPEX review meeting• Other OPEX from published sources

– OPEX from Tritium Laboratories– OPEX from H2 Handling Industry– Other published sources


Throughput - 11. TRF feed chemistry control is necessary for asset preservation.

2. Moderator swaps are more effective at reducing tritium levels in a station than online feed-and-bleed removal.

3. The duration of an outage directly impacts throughput. For good outage performance:

a. A simplified outage control center should be considered.

b. Strict scope control, well thought-out schedules and plans, and thorough risk management is needed.

c. Access to personnel can be limited and need to be planned. Personnel need to be trained for outage tasks.


Throughput - 24. Life extension actions should be integrated with regularly

scheduled outage work.

5. Use station FME controls for work on critical equipment.

6. Correct equipment set-points are needed to avoid equipment damage and thus maintain TRF throughput.

7. Preventative maintenance is essential on critical equipment to maintain throughput.


Cryogenics & Vacuum - 11. Cryogenic systems must be kept free of condensable

contaminants (everything except He and H2). Condensable contaminants in cryogenic systems can only be removed by warmup of the cryogenic system and purging or evacuating.

2. Cryogenic systems prior to cooling must be evacuated to the lowest possible pressure (i.e. highest vacuum).

3. The water vapour pressure in the cryogenic system must be maintained at a dew point of less than -80°C D2O, and if the sensor is calibrated to H2O instead of D2O, then less than -101.57°C should be maintained.

4. Dryer flooding can occur by abrupt valve closure causing seal water to be pushed into the dryers.


Cryogenics & Vacuum - 25. Dew point inaccuracies can occur due to flow and pressure

changes or by wetness forming on the dew point sensor.

6. A helium blanket on the CD1 condenser will result in a sudden condenser cooldown and a sudden unstable decrease in the refrigeration system output.

7. He must be kept to <100 ppm average concentration to avoid a helium blanket in CD1.

8. Adjust the CD1 condenser temperature manually according to the protium concentration, if CD1 is at risk of a He blanket.


Cryogenics & Vacuum - 39. All material, except H2 and He, will condense and accumulate in

CD reboilers. Station OPEX has found that this can create fouling of the reboilers or high liquid levels. Removal of contaminants is performed by warm-up and purification operations. Blockage of cryogenic pipes is also a possibility.

10. The total gaseous impurities (N2+O2) should be less than 10 ppm before linking the cryoadsorbers to the CD columns, to avoid fouling on the reboilers . Up to 50 ppm N2 is acceptable for short periods of time.

11. Gas species in air (e.g. N2, O2) are adsorbed by dryers and should be removed by evacuating the dryers.

12. A higher boilup rate reduces the risk of N2 and O2 fouling on reboilers.


Cryogenics & Vacuum - 413. Maintain leak-tightness and low vacuum pressures for

cryogenic insulation.

14. Maintain full FME control for cryogenic systems during repairs and maintenance.

15. Preventative maintenance on select valves is needed to avoid a situation where cryogenic hydrogen leaks into a non-cryogenic area or where contaminates enter the cryogenic system.

16. Good procedures, and proper procedure adherence is needed to keep the cryogenics operating well.

17. Air exposure to cryogenic temperatures could create an O2enriched environment or liquefied air with increased fire hazards.


H2 / D2 Handling - 11. Be careful of H2 accumulation points, including dead-ended or

stagnant pipes.

2. The source of ignition of H2 cannot always be identified. Catalysts are ignition points.

3. Continuous gas analysis is necessary where there is a risk of flammable mixtures.

4. Extra care must be taken to properly install components on a system containing hydrogen, including having correct instructions, the right tool for the job, and adequate technician understanding of the work.

5. Preventative maintenance is essential on critical H2 valves to minimize passing.


H2 / D2 Handling - 26. Correct equipment set-points, good procedures, and proper

procedure adherence is critical for safe handling of H2 gas and adequate response to alarms. This includes the wearing of flame retardant clothing, the use of non-sparking tools, and ensuring static electricity is removed via grounding.

7. Proper purging is required for H2 systems, which must include He purges. Always assume H2 is present and verify the system has been purged to less than 1% when performing system maintenance on a hydrogen system. Always assume O2 is present and verify the system has been purged to the appropriate level when reintroducing H2 into a system.

8. Proper training is needed for safe H2 handling.


Leaks & Emissions - 11. A mass balance simulation can be utilized to help find

mass balance errors (e.g., leaks) in the actual equipment beyond the capability of inspection equipment.

2. Equipment exposed to tritium gas can result in very high tritium surface contamination and very high tritium oxide levels. The equipment is difficult to decontaminate, since the tritium is absorbed into the material.

3. Sampling errors creates uncertainty about the tritium emission rates.

4. Tritium surface decontamination can only be performed by heating to above 200°C.


Leaks & Emissions - 25. Tritium emissions through the recombiner can be reduced by:

a. Minimizing the flow of inert gas to the recombiner,

b. Diluting the heavy water volume for high-tritium inventories,

c. Increasing the frequency of tritium emission measurements, and

d. Ensure excess O2 supplied by monitoring the temperature.

6. Being aware that dead legs can build up a tritium inventory, which can result in higher emissions during purge activities.


Leaks & Emissions - 37. Preventative maintenance is needed on critical tritium isolation

valves (e.g. isolation valves between HTD and LTD at the DTRF) to ensure recombination does not release large amounts of tritium.

8. Correct equipment set-points, good procedures, and proper procedure adherence is needed to minimize tritium emissions.


Programs and Practices - 1 1. Due to changes in the CSA N285 standards there two

types of Class 6 systems and vessels: 2 Ci/kg for CSA N285.0-06, 10 Ci/kg for older equipment. Programs, practices, and staff awareness of the mosaic of Class 6 systems is needed to avoid exceeding the 2 Ci/kg limit.

2. Tritium is not the only radiological hazard in the TRF. Other radiological material can be present and must be planned for.

3. O2 contact with getter material can create a quick and highly exothermic reaction and release tritium.


Programs and Practices - 2

4. TRF training must be based on a systematic approach to training to keep compliant with regulator expectations.

5. Proper procedure adherence is needed for safe operation.


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CANDU TRF MUST-KNOW OPEX - Energy