NRC NEWS

U.S. NUCLEAR REGULATORY COMMISSION

Office of Public Affairs Region III

2443 Warrenville Road

Lisle IL 60532

Site: www.nrc.gov

Blog: http://public-blog.nrc-gateway.gov

No. III-12-040

Contact: Viktoria Mitlyng (630) 829-9662

 Prema Chandrathil (630) 829-9663

November 2, 2012

E-Mail: OPA3 @nrc.gov 

NRC ASKS EXELON TO ADDRESS QUESTIONS ABOUT DRESDEN’S 

FLOODING RESPONSE PLAN

The Nuclear Regulatory Commission has issued a letter asking Exelon Generation Co. to

address the NRC’s concerns with Dresden Nuclear Station’s response plan for external flooding 

events. The two-unit plant is located in Morris, Ill., 25 miles southwest of Joliet.

NRC inspectors identified multiple areas of concern during recent inspections conducted 

in response to the Fukushima Dai-ichi accident. The issues pertain to the plant’s plan to respond 

to a Probable Maximum Flood – a hypothetical flooding level which postulates the largest 

conceivable flood from the combination of the most severe meteorological and hydrologic

conditions. Such conditions have never been known to occur in this area and are highly 

improbable. The issues with Dresden’s flood response plan do not represent an immediate safety 

issue but are an area the NRC would like additional information on to ensure it meets postFukushima standards.

Dresden was originally licensed for operation in 1966 for the flood value of 506.4 feet 

above mean sea level. The reactor and other plant structures were constructed at 517 feet above 

mean sea level, 10 feet above the historic flood levels. While the plant was within its design 

basis at this time, the NRC changed the flood design criteria in 1982 by basing it on a more 

stringent hypothetical flood value for the area. Dresden developed a response plan to address the 

disparity between the original and the revised design bases for flooding. 

As the agency works to enhance the protection of nuclear plants against extreme natural 

disasters after the accident in Japan, the issues with Dresden’s flood plan have come into 

stronger focus.

“We expect the plant to address the concerns with Dresden’s flood plan NRC inspectors 

identified during recent inspections looking at Dresden’s ability to deal with a hypothetical

flood,” said NRC Region III Administrator Charles Casto. “We expect our licensees to be in 

compliance with the plant’s design and licensing basis.”

The NRC has two major areas of concern with Dresden’s flood response plan:
The quality and viability of the procedure;

The availability and capability of equipment specified in the response plan to 

fulfill their intended functions.

The NRC asked Exelon to respond the NRC’s letter within 30 days by:

Addressing the list of specific NRC concerns;

Demonstrating that the existing procedures and strategies to respond to postulated 

maximum flooding events would be successful or offering alternative solutions; 

Providing a schedule for the actions the plant intends to take in response to the 

NRC’s concerns.

After the NRC receives Exelon’s response, a public meeting will be scheduled to provide 

a forum for discussing these issues with members of the public.

NRC’s letter and attachments detailing the NRC’s concerns will be available through the 

NRC’s electronic document system ADAMS under ML12306A393, or by calling the NRC 

Region III Public Affairs Office.

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