United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 94-38: Results of a Special NRC Inspection at Dresden Nuclear Power Station Unit 1 Following a Rupture of Service Water Inside Containment


May 27, 1994



All holders of operating licenses or construction permits for nuclear power
reactors and all fuel cycle and materials licensees authorized to possess
spent fuel.


The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to inform addressees of the results of a special NRC inspection at
Dresden Nuclear Power Station Unit 1 (Dresden 1) after a rupture of the
service water system occurred inside the containment.  It is expected that
recipients will review the information for applicability to their facilities
and consider actions, as appropriate to avoid similar problems.  However,
suggestions contained in this information notice are not NRC requirements;
therefore, no specific action or written response is required.

Description of Circumstances

Dresden 1, one of three boiling-water reactors at the Dresden site near
Morris, Illinois, was licensed for operation on September 28, 1959, and was
permanently shut down October 31, 1978.  On January 25, 1994, the licensee for
Dresden 1 discovered approximately 200 m [55,000 gallons] of service water in
the basement of the unheated Unit 1 containment.  The water originated from a
rupture of the service water system piping inside the containment that had
been caused by freeze damage to the system.  The NRC dispatched a team of
inspectors from the Offices of Nuclear Reactor Regulation (NRR), Nuclear
Material Safety and Safeguards (NMSS), and Region III to conduct a special
inspection of the circumstances surrounding the event.  The results of this
special inspection are contained in NRC Inspection Report No. 50-010/94001,
issued on April 15, 1994.

The licensee investigated the circumstances further and found that there was a
potential for a portion of the spent fuel pool (SFP) system inside the
containment to fail and result in a partial draindown of the SFP containing
660 spent fuel assemblies.  The licensee implemented several specific actions
to guard against further damage from freezing and appointed an investigation
team headed by a corporate official to investigate the status of Dresden 1.

9405240025.                                                              IN
94-38                                                               May 27,
1994                                                               Page 2 of 4

The NRC issued NRC Bulletin 94-01, "Potential Fuel Pool Draindown Caused by
Inadequate Maintenance Practices at Dresden Unit 1," April 14, 1994, to
request that action addressees specified in the bulletin take actions to
ensure that the quality of the SFP coolant, and the cooling and shielding for
fuel or equipment stored in the SFP is not compromised and that all necessary
structures and support systems are maintained and are not degraded.  The
bulletin also indicated that the NRC staff is reviewing the need to request
actions related to siphon or drainage paths at older operating power plants
and certain fuel cycle facilities.


The NRC inspection team evaluated the circumstances of the event and the
findings of the licensee investigation.  Based on these reviews, and as noted
in NRC Bulletin 94-01, the following conditions existed at Dresden 1:

Heating had not been provided to the Dresden 1 containment for the
1989/1990 and subsequent heating seasons.  The lack of heating inside
the containment under more severe weather conditions could potentially
have resulted in the freezing and rupture of the fuel transfer tube.
Failure of the fuel transfer tube could have drained the SFP to several
feet below the top of the stored fuel assemblies.  The loss of water
shielding would have created onsite personnel hazards from the high
radiation fields.

The water quality in the SFP was poor.  The original cleanup and cooling
system was shut down in 1983; by 1987 the water quality had degraded to
the point that an influx of microorganisms had developed.  Concerned
that the microorganisms might cause microbiologically induced corrosion,
the licensee installed a temporary system to clean up the pool.  The
temporary system proved to be incapable of restoring the water quality
to an acceptable level.  Licensee records show that the conductivity in
the pool exceeded the technical specification limit of 10 mho per
centimeter by about a factor of two.  Also, the licensee estimated that
approximately 90 stored fuel bundles had leaking fuel pins resulting in
elevated concentrations of cesium-137 of about 370 Becquerels/ml [1 x
10-2 Ci/ml].

A number of obsolete piping lines from the original pool cleanup and
cooling system remained in the SFP and were potential siphon paths that
could reduce the pool level.

Because the SFP gate was not installed it could not have prevented a
draindown of the pool if the fuel transfer pool or tunnel had emptied.
The NRC inspectors noted that the gaskets and steel mating surfaces for
the spent fuel gate had been exposed to adverse biological, chemical,
and radiological conditions that may have affected their ability to seal
had the gate been installed.

The licensee had no SFP leak detection or water inventory program.  The
observed cracks in the unlined concrete pool indicated a potential for
pool leakage. .
IN 94-38                                                               May
27, 1994                                                               Page 3
of 4

The following additional information was not included in NRC Bulletin 94-01:

Service water to Unit 1 had been isolated on January 24, 1994 because of
a rupture of service water piping in the off-gas filter building.  Had
the service water not been isolated, the leakage into the Unit 1
containment would have been greater and may have challenged containment
integrity.  A number of other pressurized water lines were isolated
outside of the Unit 1 containment but the valves were not locked out or
red tagged to provide positive control.  These lines could have flooded
the containment if opened and a rupture occurred inside the containment.

An inspection of the SFP transfer tunnel by a remotely-controlled
submersible camera found cracks in the concrete floor of the tunnel that
could be pathways for SFP water leakage.

A number of discrepancies in licensee actions with respect to docketed
decommissioning plan submittals were found.  These included (1) failure
to appoint a project manager for the Unit 1 decommissioning activities,
(2) failure to have systems operable that were stated to be operable
including a system for containment heating, (3) failure to implement a
commitment to install an Eberline Model SPING 3A air monitor in the fuel
storage building, (4) failure to have service water and certain other
systems drained or properly laid up so as not to be challenged by
temperature extremes, and (5) failure to maintain ventilation exhaust
flow rates in the containment sphere and the fuel storage building.

In addition to the above conditions the NRC inspectors also noted the
following programmatic inadequacies:

The site audit and quality verification program focused on the operating
reactors at Units 2 and 3.  Because of the emphasis on the operating
reactors, audits and safety evaluations for the site were not rigorously
implemented for Unit 1 or did not include the Dresden 1 systems and

The licensee could not provide any safety evaluation performed to
support the decision to terminate heating of the Unit 1 containment.

The inspection team concluded that the layup of the plant and storage of spent
fuel at Dresden 1 was not well managed or maintained for a period of years and
that weaknesses existed in the site quality audit and inspection programs.
Further, safety reviews of changes to Dresden 1 systems such as termination of
heating and ventilation for the containment were apparently not performed or
not adequately reviewed to determine the safety consequences of the changes.
Interviews with personnel at the Dresden site (which includes two operating
units in addition to Dresden 1) showed that, in part, the weaknesses
identified above were based on an incorrect belief that Dresden 1 could not
cause a serious safety problem because it was permanently shut down.  This
belief resulted in audits and safety evaluations that were not rigorously
implemented or that did not include the Dresden 1 systems and programs.
However, as noted above, significant safety considerations did exist.
.                                          IN 94-38
                                          May 27, 1994
                                          Page 4 of 4

This information notice requires no specific action or written response.  If
you have any questions about the information in this notice, please contact
one of the persons listed below or the appropriate NRC project manager.

/s/'d by JTGreeves/for /s/'d by AEChaffee/for

Malcolm R. Knapp, DirectorBrian K. Grimes, Director
Division of Waste Management    Division of Operating Reactor Support
Office of Nuclear Material SafetyOffice of Nuclear Reactor Regulation
  and Safeguards

Technical contacts:  James McCormick-Barger, RIII
               (708) 829-9872

               Richard Dudley, NRR
               (301) 504-1116

   Larry Bell, NMSS
   (301) 504-2171

1.  List of Recently Issued NRC Information Notices
2.  List of Recently Issued NMSS Information Notices

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