Nuclear power plant “modes” explained here

The plant’s operating status is classified under one of several “modes.” These probably won’t be explained to you on your first day on the job . . . .

When a plant is “shut down,” there are actually different levels of how shut-down a plant is at any given time. These different steps are called modes. There are a different number of modes for a pressurized water reactor than there are for a boiling water reactor, and depending on the manufacturer of each. The two  tables below are taken from the generic tech specs from Westinghouse (for PWRs) and GE (BWRs). You will hear the “mode” designator often. These tables explain what they mean.

Table 1 – Westinghouse Pressurized Water Reactor Operation Modes

Mode	Title	Avg. Rx. Coolant Temp. (℉)
1	Power Operation	N/A
2	Startup	N/A
3	Hot Standby	≥ 350
4	Hot Shutdown	350 > TAVG > 200
5	Cold Shutdown	≤ 200
6	Refueling	N/A

Table 2 – General Electric Boiling Water Reactor Operation Modes

Mode	Title	Avg. Rx. Coolant Temp. (℉)
1	Power Operation	N/A
2	Startup	N/A
3	Hot Shutdown	> 200
4	Cold Shutdown	≤ 200
5	Refueling	N/A

 

Both of these tables are published in the standard tech specs created by Westinghouse and GE. Here is the link to the NRC’s compilation of the latest versions of these two tech specs and more:

Link: http://www.nrc.gov/reactors/operating/licensing/techspecs/current-approved-sts.html

Here are the page numbers for quick referencing:

Westinghouse, Standard Technical Specifications, Volume 1: Specifications, Rev. 4, released as NUREG-1431, p. 1.1-7.

General Electric, Standard Technical Specifications, Volume 1: Specifications, Rev. 4, released as NUREG-1433, p. 1.1-7.

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