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NRC NEWS
U. S. NUCLEAR REGULATORY COMMISSION
OFFICE OF PUBLIC AFFAIRS, REGION III
801 Warrenville Road, Lisle IL 60532 |
| CONTACT: |
Jan Strasma (630) 829-9663/e-mail: rjs2@nrc.gov |
|
Angela Greenman (630) 829-9662/e-mail: opa3@nrc.gov |
NEWS ANNOUNCEMENT: RIII-96-36 July 3, 1996
CONTACT: Jan Strasma 708/829-9663
Angela Dauginas 708/829-9662
E-mail: opa3@nrc.gov
NRC ISSUES AUGMENTED INSPECTION TEAM REPORT
ON HYDROGEN GAS BURN IN SPENT FUEL CASK AT POINT BEACH PLANT
The Nuclear Regulatory Commission Augmented Inspection
Team has issued its report on the hydrogen gas burn which
occurred May 28 in a spent fuel storage cask at the Point
Beach Nuclear Power Station.
An exit meeting with the utility, open to the public,
was held June 7 at the Two Creeks Town Hall to present the
preliminary findings of the team. The report's conclusions
are consistent with those presented at the June 7 meeting.
Among the principal findings of the team's report are:
-- There was no evidence of damage to the spent fuel as a
result of the gas burn and no measurable releases of
radioactivity as a result of the gas burn.
-- The source of the hydrogen was a chemical reaction
between a zinc-based coating and the borated water from
the spent fuel storage pool.
-- Opportunities were missed to identify the potential
generation of hydrogen during the initial design, design
review, and design specifications for the spent fuel
cask.
-- The utility had several opportunities to identify the
production of hydrogen during previous cask loading
activities when abnormalities were noted. These
abnormalities were not documented and were not
thoroughly evaluated.
The Augmented Inspection Team's function was to gather
information rather than determine compliance with NRC
requirements. The team's findings will be reviewed during
subsequent NRC inspections to assess the utility's regulatory
compliance.
The executive summary of the AIT report is attached.
Copies for the 29-page report are available from the Region
III Office of Public Affairs upon request.
# # # # #
NRC AUGMENTED INSPECTION TEAM REPORT - EXECUTIVE SUMMARY
On May 28, 1996, after loading a VSC-24 ventilated storage
cask with spent fuel, an unanticipated hydrogen gas ignition
occurred inside the cask during welding of the shield lid.
The gas ignition, which was heard by plant technicians,
displaced the shield lid in the upward direction
approximately 3 inches, and cocked it at a slight angle. The
shield lid is approximately 9 inches thick, 5 feet in
diameter, and weighs slightly less then 6,400 pounds.
There was no evidence of damage to the spent fuel in the cask
as a result of the gaseous ignition. The Augmented
Inspection Team (AIT) concluded that there were no offsite
radiological consequences as a result of this event. During
this event, all possible station release pathways to the
public were monitored with no indication of abnormal
releases. The AIT further concluded that there were no
measurable releases of radioactivity from the cask and no
unanticipated radiation exposures to the staff. There were
no personnel injuries.
The licensee's actions during and following the event
including management oversight were good. However, the
inspectors identified several weaknesses in unloading
procedures, safety evaluations, corrective actions and
rigging practices.
The licensee has concluded and the AIT agrees, that the
source of the hydrogen was an electrochemical reaction of
zinc in the Carbo Zinc 11 coating when in contact with the
borated water in the spent fuel pool (SFP). The coating is
used to prevent corrosion of the multi-assembly sealed basket
(MSB). At the conclusion of the AIT inspection the licensee
had not fully completed their root cause investigation.
However, the licensee believes that opportunities were missed
to identify that the electrochemical reaction of the coating
with borated water would result in the generation of
hydrogen. Those opportunities occurred during the initial
design, design review and design specification for the VSC-24
cask.
In addition, the AIT concluded that the licensee had several
opportunities to identify the generation of gas inside of the
MSB during previous cask loading operations due to several
noted abnormalities. However, the abnormalities were not
documented, were not thoroughly evaluated, and were not
viewed collectively. This is of particular concern because
the licensee had direct indications that combustible gas was
being produced.
The AIT determined that the potential generic implications of
the event extend beyond the use of the VSC-24 system.
Consideration should be given to reviewing the adequacy of
the chemical compatibility evaluations conducted during
design reviews for all dry cask storage designs.
Consideration should also be given to determining the
suitability of Carbo Zinc 11 and other similar coatings used
in nuclear applications, where there is the potential to
expose them to boric acid.
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