NRC NEWS

 U.S. NUCLEAR REGULATORY COMMISSION

 801 Warrenville Road

 Lisle IL 60532

 Web Site: http://www.nrc.gov 

No. III-03-054 July 31, 2003

CONTACT: Jan Strasma (630) 829-9663 E-mail: opa3@nrc.gov

Viktoria Mitlyng (630) 829-9662 

DAVIS-BESSE SUMP PROBLEM PRELIMINARY SAFETY ASSESSMENT: “YELLOW”

The Nuclear Regulatory Commission has completed its review of the potential clogging of the

containment sump at the Davis-Besse Nuclear Power Station and made the preliminary determination

that it was a “yellow” finding, one of substantial importance to safety. The plant, operated by

FirstEnergy Nuclear Operating Company at Oak Harbor, OH, has been shut down since February of

last year.

The NRC found that there was improper coating material, fibrous material, and other debris in

the reactor containment that could obstruct the flow of water into the containment sump in the unlikely

event of an accident. To provide continued long-term cooling of the reactor following a loss-ofcoolant accident, water would drain into the sump and be pumped back into the reactor. The buildup

of debris on the screen for the reactor sump could restrict the flow of water for reactor cooling.

The NRC findings are contained in Inspection Report 2003-15, which was issued on July 30. It

will be available on the NRC web site: http://www.nrc.gov -- select “Davis Besse” from the list of key

topics. The inspection report will be on the Davis-Besse “News and Correspondence” page.

To correct the potential problem, FirstEnergy has installed a redesigned sump screen, providing

substantially larger surface area, and, in addition, recoated surfaces in the containment with approved

coatings and removed other sources of debris.

FirstEnergy may request a Regulatory Conference with the NRC staff to discuss the safety

significance of the sump problems or it may submit its response in writing. The NRC staff will use

any information submitted by the utility in making its final determination of the safety significance. 

The final safety significance will be posted on the NRC’s Davis-Besse “News and Correspondence”

page and at: http://www.nrc.gov/what-we-do/regulatory/enforcement/current.html

 NRC inspection findings are evaluated using a four-level scale of safety significance, ranging

from "green" for a finding of minor significance, through "white" and "yellow" to "red," for a finding

of high safety significance. A yellow finding is one of substantial safety significance.

Normally, yellow findings can lead to additional NRC inspections and meetings with the utility. 

In the case of Davis-Besse, however, the plant is already subject to numerous inspections and an NRC

oversight panel is monitoring the plant’s activities in response to damage to the reactor vessel head

which was found in March of last year.
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The NRC inspection report discusses an additional issue, unrelated to the sump finding,

concerning the high pressure injection pumps, which are part of the plant’s emergency core cooling

system. This issue involved potential damage to the pumps’ bearings from debris in water pumped

from the containment sump under certain accident conditions. FirstEnergy is currently modifying the

pumps to correct this potential condition. The NRC staff is continuing its review of the high pressure

injection pump issue to determine its safety significance.

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