Guide to Emergency Classifications and Declarations at U.S. Nuclear Power Plants

David LochbaumUnion of Concerned ScientistsMay 2012

Emergencies at U.S. nuclear power plants are classified into four severity levels by plant owners and reported to the Nuclear Regulatory Commission (NRC).

Over the past decade, plant owners have declared:

• no General Emergencies• two Site Area Emergencies• dozens of Alerts• dozens of Unusual Events

The Three Mile Island accident in 1979 resulted in extensive upgrades to the emergency procedures and training used to classify emergencies.

The emergency procedure charts developed for the Ginna nuclear plant in New York can be found in the NRC’s ADAMS electronic library (see http://www.nrc.gov/reading-rm/adams.html) under Accession Nos. ML12037A117 and ML12037A118.

The emergency procedures for Ginna consist of more than 800 pages that assist the operators put the chart’s information in context (see ADAMS ML12037A116). Operators receive extensive training on these emergency procedures.

They are comparable to procedures used elsewhere and will be used here to explain how operators determine when to declare what emergency level.

This arrangement guides operators to the first configuration that exists, rather than to the first one that does not exist. This arrangement guards against operators declaring a lower severity emergency when conditions exist for a more severe emergency.

The reactor has seven modes of operation.

Some emergency conditions are only applicable when the reactor is in certain modes; other emergency declarations are applicable in any mode.

Mode 1 – The reactor is operating above 5% power

Mode 2 – The reactor is operating below 5% power

Mode 3 – The reactor is not operating and its water temperature exceeds 350°F

Mode 4 – The reactor is not operating and its water temperature is 200-350°F

Mode 5 – The reactor is not operating and its water temperature is below 200°F

Mode 6 – The reactor is not operating with the reactor vessel head removed

Defueled – There is no fuel in the reactor core.

The upper right corner of the first emergency procedure chart will be used to explain the classification process.

This row addresses emergencies resulting from problems controlling the reactor power level. [RPS stands for the Reactor Protection System, which automatically trips the reactor – causes control rods to insert within seconds – upon detection of abnormal/undesired plant conditions. The operators can also manually trip the reactor using the RPS.]

If an automatic or manual trip of the reactor was initiated, but failed to stop the nuclear chain reaction AND the operators were not able to stop the nuclear chain reaction or reduce the reactor power level to below 5 percent AND conditions suggest reactor core cooling is inadequate, a GENERAL EMERGENCY is declared.

If an automatic or manual trip of the reactor was initiated, but failed to stop the nuclear chain reaction AND the operators were not able to stop the nuclear chain reaction or reduce the reactor power level to below 5 percent, a SITE AREA EMERGENCY is declared.

If an automatic or manual trip of the reactor was initiated, but failed to stop the nuclear chain reaction AND the operators were able to stop the nuclear chain reaction or reduce the reactor power level to below 5 percent, an ALERT is declared.

When the reactor power level increases unexpectedly while in Mode 3 or Mode 4, an UNUSUAL EVENT is declared.

It is possible that a single event could cause conditions to appear in more than one row of an emergency procedure chart. If so, the most severe emergency classification level is selected.

The emergency classification determines the appropriate onsite and offsite response level.

Technical Support Center (TSC), typically manned in 30 to 60 minutes, is responsible for monitoring conditions, engineering support, and onsite radiological monitoring.

Operations Support Center (OSC) coordinates craft workers performing damage recovery efforts

Emergency Offsite Facility (EOF) interfaces with offsite agencies, estimates radiation doses, and makes recommendations for protecting the public

Time to mount the soap box.

The lower left corner of the first emergency procedure chart will be used to show, once again, the well-recognized but shamelessly downplayed relative hazards of spent fuel pool vs. dry storage.

Spent fuel pool cooling problems could lead to fuel damage necessitating a GENERAL EMERGENCY.

However, dry storage of spent fuel in an Independent Spent Fuel Storage Installation (ISFSI) can – at most – require an UNUSUAL EVENT to be declared.

However, dry storage of spent fuel in an Independent Spent Fuel Storage Installation (ISFSI) can – at most – require an UNUSUAL EVENT to be declared.

POP QUIZ

What poses the higher hazard:

1) Irradiated fuel in spent fuel pools

2) Irradiated fuel in dry storage

3) Pretending that spent fuel pools and dry storage have the same risk

POP QUIZ

What poses the higher hazard:

1) Irradiated fuel in spent fuel pools

2) Irradiated fuel in dry storage

3) Pretending that spent fuel pools and dry storage have the same risk