ML20006E318
| ML20006E318 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 02/09/1990 |
| From: | Scace S NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| MP-90-150, NUDOCS 9002220640 | |
| Download: ML20006E318 (6) | |
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February 9,-1990.
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Re:. Voluntary Report.
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- U.S; Nuclear Regulatory Commission.
Document ' Control Desk.
yWashington, D,C. 20555 n:
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Reference:
Facility Operating License No. DPR-21 Docket No. 50-245 1
Licensee Event Report Information Letter r
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Gentlemen:
.a r Northeast Nuclear Energy Company has determine'd that the event described in the ac- -
icompanying document-is not recortable per 10CFR50.73. ~ This letter forwards the at -
2 ached Licensee Event ReportInformation Letter. This report provides information con-
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'cerninc a radioactive. materials shipment to the Duane Arnold Energy Center.
. Very truly yours, y
NORTHEAST NUCLEAR ENERGY COMPANY t
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' Steph n E.'
cace Director, Millstone Station:/
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SES/CRP:mo 7
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Attachment n'
cc: W; T. Russell, Recion 1 Administrator -
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W. J. Raymond, Senior Resident Inspector, Millstone -Unit.Nos.1. 2 and 3 4:
f' M. Boyle, NRC Project Manager, Millstone Unit No.1 w
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9002220640 900209 f
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High Dose' Rate on Radioactive Material Shinment x
. Abstract '
On Friday,; January 19, 1990, the Millstone Radioactive Materials' Handling (RMH)
Supervisor was notified by the Radwaste Supervisor at the Duane Arnold Energy
,1 Center that a radioactive materials shipment (LSA, exclusive use, flatbed trailer) r arrived at Duane Arnold Energy Center with a contact reading in excess of the limits i
allowed for the package (200 mR/hr) per 49CFR173.441(b)(1). Duane Arnold-manacement made a notification of the incident to NRC Recion III Headquarters, who
'in turn notified NRC Recion 1 Headquarters. This resulted in' a notification to the
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Millstone Resident inspectors Office.
The shipment in question was a contaminated underwater shear cutter (USC), owned by WasteChem Corporation which had recently been used to process control rod blades in the Millstone Umt 1 fuel pool Surveys on the package prior to'its departure from Millstone Station indicated that the maximum surface dose rate on the package was 90 mR/hr. -Readings taken at the Duane ' Arnold Energy Center indicate that the maximum contact dose rate was 250-300 mR/hr in a 3" by 5" area located approximately one foot from the highest reading (90 mR/hr) observed by Millstone' Radioactive Materials
. Handling personnel.. Evaluation by the Health Physics Staff at the Duane Arnold Energy: Center indicated that the source of the elevated radiation level was due.to a hot spot on a chute in the lower section of the USC. This area did not have a dose l
rate of more than 50.mR/hr when Millstone Unit 1 Health Physics personnel surveyed the unit prior to packaging.
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Descrintior. of Event The shipment in question contained a USC owned by WasteChem Corporation which was used in Millstone Unit 1 to cut control rod blades. It was shipped from the Millstone Station on Wednesday, January 17,1990 and arrived at the Duane Arnold Energy Center on Friday, January 19, 1990.
The USC is a hydraulically controlled press and shear, capable of generating 30,000 psi on the press face its primary function is to flatten a control rod blade and then cut it into desired lengths. Under the shear area is a bucket to catch the cut items. The bucket is connected to a hydraulic cylinder that moves it either under the shear or to an open box area where sheared items can be removed.
The USC is-controlled'by a hydraulic pressure unit that consists of a low pressure pump, a high pressure pump, a demineralized water reservoir, a series of control valves, and a remote control station. All USC cutting operations are conducted underwater in the spent fuel pool.
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The cutting machine arrived at the Millstone Station on November 8,1989.
Receipt surveys on the box were performed by Health Physics technicians assigned to the Radioactive Materials Handling organization. The shipment was found to be in compliance with DOT requirements. The USC was operated in the Millstone spent fuel pool at various times during November and December.
Upon completion of the work, the underwater shear cutter was decontaminated in preparation for shipment. This included the following activities:
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- J,To reduce dose rates'on' the USC, a decontamination effort usinc a -
i ydrolazer was initiated in the spent fuel pool. After decontamiilation, a h
_ survey was performed to identify those areas where high radiation levels; p'
3ersisted/ This process was repeated for four-cyclesc However, several_.
lot spots were noted on the:USC that could not be removed by 5
hydrolazing..
The USC was removed from the fuel pool and moved to a tent on the' refueling floor. A survey was performed identifying areas for further decontamination.
'o The unit was wiped down, resulting in further reduction of hot spotsEA 1.5 R/hr hot spot in a weld seam that apparently resisted the hydrolazing-f.
could not'be reduced by wiping,
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The 1.5 R/hr hot spot was assessed by Unit 1 Health Physics personnel to be fixed in the weld-seam. A scanning survey of the lower section of the:
n unit indicated that, not. withstanding the hot spot, the shippine limits on the package surface would not likely be exceeded.
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The USC was then wrapped in plastic and placed into its shipping
, package. The package contents were braced into place.
A radiation survey was done on the shipping package and it was deemed to be in a satisfactory condition for final preparation by the RMH personnel.
The package was' then transported to RMH personnel for the shipping preparations.
This effort required'nearly 140 manhours and expended 0.89 man rem: -(Includes.
. all labor).
Radioactive Materials Handling personnel prepared the package for shipment,-
including the following activities:
'A detailed survey of the package was completed.. Due.to the size of the
- i box and the detailed level of the survey, this effort required' approximately six manhours. The result.of this survey indicated 'that the -
maximum contact dose rate on the box was 190 - 200 mR/hr. This area was approximately three inches square.
A joint inspection of the box and its contents by Health Physics.
techricians from the Radioactive Materials Handling group and Unit 1 concluded that the maximum contact dose rate on the package was directly below the fixed 1.5 R/hr hot spot on the USC.
Dunnage was added to the outside of the package over the central area i
where the hichest contact dose rate was found. The dunnace was banded
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to the box - the full width of the box over the entire central section.
The additional packing materials lowered the maximum contact dose rate on the shipping package to 90 mR/hr, well below the Millstone Station-administrative shipping limit of 160 mR/hr for a package on an open
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transport vehicle.
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The package was placed on a flatbed truck and was shipped as LSA, exclusive i
use, open transport vehicle. At the time of departure from the Millstone Station, the vehicle was in compliance with all NRC and DOT requirements for the shipping of radioactive materials.
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Upon arrival at the Duane Arnold Energy Center, a survey was performed on the i
shipment, and a readinc of 250-300 Mr/hr was found on the package surface in an
. area approximately 3" 'x 5" on the bottom of the package. The Millstone Radioactive Materlah Handling Supervisor was promptly notified of the results.
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The instrument used by Duane Arnold personnel was the Teletector. The Millstone RMH Supervisor, believing that this was not the most appropriate instrument to use for a contact reaoing, requested that another survey se performed, using an' E-520 survey meter. A subsequent survey was performed, using the E-520, by the Duane Arnold staff. The meter went off-scale on the 0-200 mR/hr range, the highest range for which the external probe can be used. The location of the hot spot was such that it was not readily accessible to personnel. The area in question
.j was not accessible by the whole body. The reading beneath the trailer,' under the 1
hot spot, was 30-45 mR/hr - well within the transportation limits for the trailer.
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The location of the high reading observed by the Duane Arnold staff was about one foot from the area of the highest reading that was observed by the Millstone staff. It was in an area where the dunnage had not been applied. The preliminary conclusion made by Millstone personnel was that something happened -
to the shipment enroute to Duane Arnold -- most probably movement of
. radioactive materials such as a small metal fracment. Movement of the unit i
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within the package is not possible since the unit was securely bolted in the box.
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The Millstone Radioactive Materials Supervisor contacted his counterpart at Duane 4
Arnold and requested that this issue be evaluated during unpacking of the unit.
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Specific data was requested during various stages of the unpacking operation.
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Follow-ua surveys of the equipment were taken by Duane Arnold Energy Center aersonne! and transmitted to Millstone the following day. The conclusion reached-ay the Duane Arnold staff was that a 1500 mR/hr spot in the chute area was the cause of the elevated packace dose rate. The cutting unit was then placed into service at the Duane Arnold Energy Center. A survey of the shipping package.
showed no elevated radiation levels after removal of the underwater shear cutter.
This indicates the source of the hich external dose rate was still on the shear
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II. Cause of Event The WasteChem underwater shear cutter was decontaminated, packaged, and shipped from the Millstone Station with considerable effort taken to ensure that actions were performed in accordance with all requirements of the NRC, DOT, and station procedures. Sometime during transport, a hot spot in the shipment
,L apparently moved, changing the external surface dose rates on the package.
The root cause of this high dose rote on the extuion surfece of the package was the inability, despite the efforts on the part of Millstoi e personnel, to ' identify i
detectable prior to shipping. particle / fragment in the s1.ipping package that w potential movement of a hot l
Based upon evaluations done at the time of p
decontamination, it was believed that all major hot spots on the cutting unit were fixed and not readily transportable. This conclusion proved to be incorrect.
Contributine to this event is the overall desicn of the cuttinc unit which has considerable internal areas for potential entr'apment of cutti'ng debris.
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Ill Anahn of Event Although it appears that the 49CFR limit for the maximum surface dose rate on
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.the sackage was exceeded upon arrival at the Duane Arnold Energy Center, the fina' dose rate did not increase the risk to the general public. The area m question was approximately 3" by 5" on the bottom of a 26,000 pound box on a.
flat bed trailer. The contact reading on the trailer beneath the hot spot was 30 -
40 mR/hr. No whole body dose in excess of 200 mR/hr could have been obtained due to the location of the spot. All other dose rates associated with the shipment were in conformance with DOT reculations. No risk, above and beyond the risks -
deemed acceptable by the regulations would be experienced by med1bers of the o'
general public.
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The shipment was transported by an exclusive use vehicle. This precluded handling the package by personnel not authorized to receive and/or handle radioactive materials durinc conditions normal to transportation. Upon receipt at the Duane Arnold Energy Denter, the package was surveyed by qualified and.
knowledgeable personnel in accordance with the regulations. No additional risk to workers was experienced as a result of this event.
IV, Corrective Action Based upon this investigation. opportunities for improvement in the shipping of i
. equipment with a high potential for radioactive particle movement have been i
identified:
-1. For such shipments, additional pre-shipment supervisory reviews shall be done. The purpose of this review will be to evaluate the potential for i
radioactive particle transport in the shipping package and to define measures to be taken to ensure compliance.with the regulations should this trans) ort occur.. The review shall be done jointly by the Radioactive Materials F andling Supervisor and the Radiation Protection Supervisor ~ of the Unit involved.
a Additional controls, specific to the shipment shall be ifuded in the inspection plan required by the Automated Work Order (AWO). f.ie resulting inspection alan will be reviewed and approved by the Health Physics Manager, Su) port.
Procedure changes to include the above recommendat' ions will be comp eted by February 28,1990.
-2. As a normal practice at the Millstone Station, future vendor contracts for.
special cutting services will include provisions for the vendor to either supply a package which can be loaded into a closed transport vehicle or to provide a personnel barrier for use on an open transport vehicle. Use of the closed.
L transport vehicle allows for packages of up to 1,000 mR/hr contact surface dose rate. This extra safety marcin recognizes the extreme difficult)*
I associated with the assessment of transportable radioactive particles in the shipping package. The level of effort to keep the package surface dose rates as low as reasonably achievable will not be diminished as a result of the extra safety margin.
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