According to multiple reports from news outlets in Taipei and South Korea, Samsung's Pyeongtaek fab experienced a power outage on March 9, 2018. The outage lasted for only thirty minutes, but the impact can be calculated in dollars per second.
Up to 60,000 wafers were damaged, according to the report, which is 11% of Samsung's overall NAND flash output for March. That equates to 3.5% of global NAND wafer production.
Increased global production from Samsung and its rivals should offset the the loss globally. These companies enjoy a small stockpile of flash memory that didn't exist last year due to strong demand and lower production output as companies shifted to new 64/72-layer memory.
We've yet to see market reaction to the March 9 event, but with word spreading rapidly, we may see some price increases overnight. Any price changes should subside quickly with the Pyeongtaek fab running at planned capacity again.
At the end of the month, Samsung will begin the expansion of the Xi'an factory that was built in 2014. The factory currently produces around 120,000 wafers per month, but the expansion will add another 200,000 to the monthly capacity after completion. However, Samsung's competition also plans aggressive expansion in the years to come.