LEADER Task 3.3 ALFRED - Primary Cover Gas System (PCGS)

LEADER Task 3.3ALFRED - Primary Cover Gas System (PCGS)

L. Mansani, M. Bruzzone, V. Pierantoni

Karlsruhe, November 20th, 2012

LEADER WP3 Technical Meeting, KIT Town Office Ostendorfhaus Weberstraße 5, Karlsruhe, 20-11 2012

TABLE OF CONTENTS

1. System Functions• Safety-Related Functions• Non-Safety Related Functions

2. Cover Gas Composition

3. Primary Cover Gas System Design Configuration• System Configuration Requirements• System Configuration

4. System Alignments• Normal Plant Operation• Plant Shutdown before Maintenance• Nitrogen Purge and Argon Recovery

TABLE OF CONTENTS


1. PRIMARY COVER GAS SYSTEM FUNCTIONS

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Non-Safety Related Functions

Contribute to maintain the integrity of the Primary Boundary during all plant conditions

Primary Boundary Integrity

Molten Primary Coolant Inertization

Maintain and control a slight argon underpressure in the primary cover gas volume

and keep up the required inertization status of the molten primary coolant

Safety Related Functions



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Non-Safety Related Functions (cont.)

Nitrogen Purge & Argon Recovery

To purge the nitrogen flowing from Reactor Hall into the Reactor Vessel during

maintenance, restore the argon atmosphere and re-establish underpressure conditions

inside the Reactor Vessel before every startup

Containment of Radioactive Releases

To maintain the radioactive releases to the Reactor Hall below the design limits by

providing the mean for purification of the primary cover gas bulk mass



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Primary Heat Exchanger Leakage Detection

Timely to detect a small leak of the primary heat exchanger and provide the way to

condense and collect vapor and trap the radionuclides entrained by the vapor stream

Fuel Cladding Failure Detection

To detect failure in fuel assemblies cladding by monitoring increased primary cover gas

activity originated by fission products circulating in the primary coolant

Non-Safety Related Functions (cont.)

LEADER WP3 Technical Meeting, KIT Town Office Ostendorfhaus Weberstraße 5, Karlsruhe, 20-11 2012 7

2. PRIMARY COVER GAS COMPOSITION


From EUROTRANS: “the volatility of all the investigated elements (Po, Cs, Sr and I) is depressed, typically by several orders of magnitude, through strong chemical interaction with the heavy metal coolant. The strong retention of fission products constitutes a considerable advantage with lead and LBE coolants”. “In lead coolant (EFIT) the production of 210Po is about three orders of magnitude smaller, and the amounts of volatilized 210Po are correspondingly lower. In both XT ADS and EFIT, volatilization of 90Sr is completely negligible.”

Molar fraction passed to the gas phase



• The activity in the Cover Gas comes from a fraction of the radionuclides present in the primary lead coolant that have vaporized into the gas phase

• The radionuclides in the primary lead have two different sources: – The activation products resulting from the coolant interaction with the

neutrons– The activity released from the damaged fuel rods in case of fuel damage

• Due to the retention property of Lead the more significant radionuclides present in the Cover Gas are Noble Gases and Tritium

• Ne 235,54E-11

• Ne 244,83E-18

• Ar 394,69E-05

• Ar 419,89E-12

• Ar 421,20E-10

• Ar 432,06E-15

• Ar 454,25E-17

• Xe1271,21E-15

• Xe129m 3,75E-13• Kr 81

5,92E-13

Preliminary activation product evaluation –Noble Gases composition after 40 years (grams)



3. PRIMARY COVER GAS SYSTEM CONFIGURATION

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3. PCGS CONFIGURATION

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Provision of two (2) piping penetrations on the Reactor Cover for PCGS gas extraction and

return flow• Comply with Reactor Cover penetration Layout

• Minimize the chances of preferential gas streams capable of bypass the circulation of the RV ceiling

System Configuration Requirements

Provision of buffer tank to compensate passively for gas pressure variation due to LBE

temperature transients

Provision of a blowers station with the performances required by the PCGS purification

function to force recirculation of the Reactor Vessel ceiling through the filtration banks



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Provision of an electrical heater in the blowers station discharge pipe to increase the gas

temperature back to the current Reactor Vessel ceiling temperature, during primary cover gas

recirculation and purification

Provision of an argon storage tank to store and supply the amount of argon necessary to

recover the primary cover gas for normal operation of the PCGS

Provision of a argon supply electrical heater to support argon heat up from low

temperature to a temperature high enough to prevent LBE from experiencing thermal shocks

during plant startup conditions recovery via nitrogen purge and argon flushing operation

Provision of a single blower to purge the nitrogen flowing from Reactor Hall into the

Reactor Vessel after maintenance, restoring the argon atmosphere and re-establishing

underpressure conditions inside the Reactor Vessel before every start-up



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Provision of an HIGH temperature and a LOW temperature gas coolers to reduce the

primary cover gas temperature to suitable values for purification

Provision of a fine-dust filter and an HEPA filters bank for removal of remaining fines

post purification upstream of the blowers station suction

Provision of activated carbon beds to temporary entertain Xenon and Krypton, allowing

that delay period significantly reduces the radioactivity of the gas flow leaving this section

Provision of a Tritium treatment station to collect tritium released in the primary cover

gas


4. SYSTEM ALIGNMENTS



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Normal Plant Operation



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Before Maintenance



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Nitrogen Purge and Argon Recovery


Thank you for your attention

Documents

LEADER Task 3.3 ALFRED - Primary Cover Gas System (PCGS)