Hydrogen mitigation systems

In case of an accident in a nuclear containment where hydrogen is liberated and distributed within the building, a variety of methods can be employed for hydrogen mitigation [16]  

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The possibility of pressure relief through the banana wall was addressed witli several MELCOR calculations assuming instantaneous confinement pressurizations of 4,4.5, 5, mid 6 psi, a small LOCA, and nitrogen injection from the hydrogen mitigation system. These calcul.aiions showed the response of the banana wall to various confinement pressurizations. 

Containment and Severe Accident -Double Containment -Cavity Flooding System(CFS) -Hydrogen Mitigation System - Single Containment In-Vessel Retention - Replacement of Fusible Plug with MOV (Motor Operated Valve) Passive Auto-catalytic Recombiner -i- Igniter Accident mitigation Measure such as IVR adopted... 

The System 80+ Standard Design includes the Hydrogen Mitigation System (HMS) for control of combustible gas concentration in containment during and following a degraded core accident. The HMS, which is designed in accordance with the requirements of 10 CFR 50.34(f), is described in CESSAR-DC Section 6.2.5. 

Since the containment design provides a Hydrogen Mitigation System that meets the requirements of 10 CFR 50.34(f) for the control of hydrogen generated in a degraded core accident, and provides reasonable assurance of the survivability of the components essential for a subsequent safe shutdown, this issue is resolved for the System 80+ Standard Design. 

To assure containment integrity, the hydrogen mitigation system (HMS) will keep the containment hydrogen concentration below 10% to preclude detonations during and after a severe accident. 

Schatz, K.W. and Koopman, R.P. (1989) Effectiveness of Water Spray Mitigation Systems for Accidental Releases of Hydrogen Fluoride, summary report and volumes I-X, NTIS, Springfield,... 

USE OF PSA FOR DESIGN OF EMERGENCY MITIGATION SYSTEMS IN A HYDROGEN PRODUCTION PLANT... 

Use of PSA for design of emergency mitigation systems in a hydrogen production plant using General Atomics SI cycle technology. Section II Sulphuric acid decomposition... 

The reactor and the hydrogen production system are connected by the helium gas loop. A chemical reactor causes the temperature fluctuation of the secondary helium gas by the fluctuation of the chemical reaction that occurs at the normal start-up and the shutdown operation as well as malfunction or accident of the hydrogen production system. If the temperature fluctuation is transferred to the reactor, the reactor will be stopped. Therefore, the control technology should be developed to mitigate the temperature fluctuation within an allowable range to keep reactor operation, using a thermal absorber. JAEA proposed to use a steam generator (SG) as the thermal absorber that is installed downstream the chemical reactor in the secondary helium gas loop. 

The explosion of combustible gas is a very severe problem to keep the reactor safety. The problem can be considered as overpressure caused by blast to the safety-related components. There are three principal countermeasures against explosion, that is, i) place a distance between the reactor and the hydrogen production system enough to mitigate the overpressure within an allowable range, ii) limit the leak amount of combustible gas, and iii) protect blast with barriers such as wall, bank and so on. As for the hydrogen production system connected to HTTR, the countcnncasure-ii) was mainly considered. 

In the design of the HTTR hydrogen production system (HTTR-H2), SG is installed as the thermal absorber downstream the chemical reactor in the secondary helimn gas loop to mitigate the temperature fluctuation within 10°C at the SG outlet, because the temperature rise above 15 °C compared with the normal temperature at the reactor inlet causes the HTTR reactor scram [3],... 

As a result, it was confirmed that SG can be used as athermal absorber to mitigate the temperature fluctuation of the secondary helium gas caused by the chemical reactor. This technology can keep reactor operation at normal start-up and shutdown operation as well as malfunction or accident of the hydrogen production system. 

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