Nuclear reactors nuclear thermo / neutron instability protection procedures

摘要

A method of protecting the core of a nuclear reactor from damage to the fuel due to thermo-hydraulic instability in an extended operating domain for an extended power increase, comprising: generating an operational flow-power map, comprising: establishing a natural circulation curve; establish a control rod line of maximum extended load line limit analysis (MELLLA); and establish a higher MELLLA + control rod line positioned on the MELLLA control rod line; form a MELLLA + domain on the line of the MELLLA control rod, to the top line of the MELLLA + control rod; allowing operation in the MELLLA + domain and characterized by calculating a thermo hydraulic stability limit using a thermo hydraulic code simulator; determine a power level that corresponds to the thermo hydraulic stability limit at different core flow rates; provide a biased flow emergency stop line of the average power range monitor (APRM); lower the APRM biased flow emergency stop line below the thermo hydraulic stability limit; and activating an APRM-based activation system when the core flow decreases as a result of a decreasing transient flow and the power increases above the power level to provide an automatic preventive emergency stop or a rod insertion activation selected to cause a reduction in power