ML20210G971

Informs That on June 9,two Occurrences of Hydrogen Burns Took Place at Palisades During VSC-24 Loading Activities

ML20210G971
Person / Time
Site:	Palisades
Issue date:	06/16/1999
From:	Oconnor S NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
To:	Eng P NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
Shared Package
ML20210G839	List: ML20210G835 ML20210G879 ML20210G887 ML20210G909 ML20210G936 ML20210G941 ML20210G961 ML20210G971
References
FOIA-99-264 NUDOCS 9908030245
Download: ML20210G971 (1)

Text

) Steve O'Connor Pclisades _

pyg, 3 Nf From: Steve O'Connor To: Patncia Eng . N Date: Wed, Jun 16,199911:38 AM

Subject:

Palisades Pat, As you requested, the following is a synopsis of the Palisades event:

On June 9, two occurrences of hydrogen bums took place at Palisades during VSC-24 loading activities.

The flame was caused by hydrogen ignited at the outlet of the cask vent line by grinding sparks during welding activities on the structural lid. The vent line (plastic tubing) outlet was located too close to the work area and had become detached from the HEPA filter inlet (secured with duct tape).

On June 10, Region 111 issued a Preliminary Notification to discuss details of the events. Also on June 10, Palisades put a hold on cask welding activities and assembled an incident response team to examine the root cause of the event. On June 11, Palisades had re-routed the vent line using a braided stainless steel hose with the outWt located farther away from the welding activities and more rigidly affixed connection to the HEPA filter.

Palisades performed re-training of welders and continued the structural-lid welding the attemoon of June

11. A Region lliinspector (Landsman) was also present to observe the continuation of welding activities.

Welding and NDE of the cask welds were completed without any further incidences.

Let me know if you have any questions.111 be sure to keep you informed if I hear anything new.

Steve l

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- PNO-III-99-031 ! Palindes 1 n* n-v Notificarian 64 l News and Information l Main NRC Home Pane ! E-mad June 10, 1999 i

-PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-III-99-031

~ This preliminary notification constitutes EARLY notice'of events of POSSIBLE l safety or public interest significance. The information is as initially )

received without verification or evaluation, and is basically all that is known by Region III staff (Lisle, Illinois)'on this date.

Facility. Licensee Emergency Classification Consumers Power Co. Notification of Unusual Event Palisades 1 Alert Covert, Michigan- Site Area Emergency Dockets: 50-255 General Emergency X Not Applicable

Subject:

MINOR HYDROGEN BURNS DURING CASK WELDING ACTIVITIES At about 5:00 p.m., and again at about 7:30 p.m. EDT on June 9, 1999, minor hydrogen burns occurred during welding of the structural lid on a spent fuel storage cask following its loading earlier in_the week. These brief. hydrogen burns occurred outside the cask at the discharge end of tubing being used to draw gases from the interior of the cask.

The cask was the fourteenth to be loaded at Palisades and the first since cask loading activities resumed. Storage cask loading activities had been halted to address issues identified following a hydrogen burn inside the cask during loading in May 1996 at the Point Beach plant and to address subsequent welding issues. involving the_ Sierra Nuclear VSC-24 cask.

Loading of 24 fuel assemblies-into the cask was completed on June 7 and the cask, still containing water for radiation shielding purposes, was removed from the spent fuel storage pool. The inner shield lid had been welded in place, and workers had begun welding the structural lid.

The cask was still' filled with water,_and the small air space at the top was being ventilated through a small plastic tube to remove any hydrogen being produced in the cask. One end of the tube was connected to the cask and the other to a filtering device. The tubing became separated from the filter, and sparks from the grinding ignited the hydrogen at the discharge end of the tubing. In each instance the welder observed a small

' flame at the end of the. tubing, pinched the tubing, and extinguished the flamei Work was stopped following the second incident, and the licensee's spent fuel storage cask group was notified. The discharge end of the ventilating tubing was reconnected to the filter unit and work activities were resumed. Plant management was not informed until the morning of June 10, 1999. At that time, a second work halt was imposed by plant management pending further review.

.The use of a ventilating system on the cask has been standard practice at Palisades. It is also one of the corrective actions following the Point Beach hydrogen burn event, to prevent a combustible accumulation of hydrogen inside the cask. The hydrogen is produced through a chemical reaction between boric acid in the water inside the cask and the zinc-based coating on the cask interior. As long as the boric acid in the

. water is present in the cask, hydrogen will be produced. When the welding 'r

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• i 'is completed,- the water. will be removed and the cask will be filled with helium.

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This hydrogen burning was of minor safety. significance. The burning was outside the_ cask at-the discharge of the tubing, and no air was being added-to.the cask itself that would support ignition of any hydrogen

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inside.the cask. The flames were easily extinguished. No injuries or squipment damage'resulted. The presence of hydrogen was an expected phenomenon, and the ventilation system was functioning to prevent the accumulation of a potentially combustible concentration inside the cask.

-The NRC. resident inspectors will follow the licensee's response to the incident and observe when the licensee resumes work. Also, a special NRC inspection on cask loading activities is ongoing, and a cask team inspector was onsite until after the shield lid weld was completed,

.although rione of the cask team were onsite at the time of the incidents.

These incidents will be~ reviewed when a team member returns to the site to continue the inspection next week.

The Stet's of Michigan was ' informed. The information in this preliminary notification has been reviewed with licensee management.

Region III (Chicago) learned of these this event at about 8:00 a.m. CDT on 7une 10, ' 1999. This information is current as of 12:45 p.m. on June 10, 1999.

Contact:

ROSS LANDSMAN BRUCE JORGENSEN (630)829-9609. (630)829-9615 i

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.U 6/30/1999 6.49 AM l12 hf2 ,