Junk Plant Grand Gulf: 91% Power Scram Is So Unprofessional

On January 30, 2018, Grand Gulf Nuclear Station (GGNS) was operating in Mode 1 at 91 % power and was in the process of. increasing power. At 1739 hours CST on January 30, 2018, GGNS experienced main turbine control valve (TCV) position changes of between 3 and 5 percent and main generator output load cha.nges of approximately 20 megawatts with a periodicity of approximately 3 seconds.

At 1822 on January 30, 2018, operators performed a manual shut down of the reactor by moving the reactor mode switch from RUN to SHUTDOWN to place the unit in Mode 3. Upon reactor shutdown all systems performed as designed and no subsequent safety system actuations occurred. The cause of the manual shutdown was conservative operator response to unanticipated main turbine generator output changes. Corrective actions include adjustments to the control circuit, and revision of work task documents for adjustment of the control circuits.
There wer~ no consequences to the general safety. of the public, nuclear safety, industriai safety and radiological safety for this event.
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