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MH-1A Loss of Flow Transient Safety Analysis and Parametric Study.

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Final rept.,

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The loss of coolant flow transient for the MH-1A has been investigated. Commercial central station practice with regard to this transient was surveyed and indicated that a loss of power to all primary coolant pumps with the reactor initially at the limits of the normal operating bands should be the transient considered in the plant safety analysis. The appropriate fuel failure criterion is departure from nucleate boiling. Two-pump and one-pump loss of flow transients for the MH-1A were analyzed to determine the conditions in the nominal and hot channel of the core during the transient. In addition to values which correspond to the operating band limits of reactor power, coolant flow, inlet temperature, and pressure initial conditions were considered which varied from the simultaneous occurrence of scram setpoint values to nominal full power conditions. For all cases considered, the minimum departure from nucleate boiling ratio was well above the minimum acceptable value. The potential for hydraulic instabilities during the loss of flow transient was considered. Two-phase flow regime maps were used to indicate possible flow regime transitions which could cause flow oscillations. When the loss of two pump transient is initiated from operating band limits modified to conservatively allow for instrument error, a momentary transition to slug flow was found. Information in the literature and BWR design practice indicates this is of no concern. It is concluded that the most severe credible loss of flow transient will not result in damage to the MH-1A reactor.

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  • Nuclear Power Plants and Fission Reactor Engineering

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