ML20009G683
| ML20009G683 | |
| Person / Time | |
|---|---|
| Site: | 07001308 |
| Issue date: | 07/16/1981 |
| From: | Greger L, Peck C NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML20009G672 | List: |
| References | |
| 70-1308-81-02, 70-1308-81-2, NUDOCS 8108040548 | |
| Download: ML20009G683 (8) | |
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9 U.S.~ NUCLEAR REGULATORY. COMMISSION 0FFICE OF. INSPECTION AND ENFORCEMENT
'l REGION.III.
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Report No. 70-1308/81-02--
-Docket No.'70-1308.
License No. SNM-1265
-Licensee:. General Electric Company 175 Curtner-Avenue San' Jose, CA 95125 Facility Name':. Morris Operation Inspection At: Morris Operation, Morris,'IL
. Inspection Conducted: May 31 and June 5-7, 1981 0.8,7N$lp Inspector:
C.,C. Peck 7" P/
<9.f, 7?tl$hvlfv Approved By:
L. R. Greger, Acting Chief 7-N-8/
-Facilities Radiation Protection Section l
L Inspection Summary:
Inspect.'on on May 31 and June 5-7, 1981 (Report No. 70-1308/81-02) l.
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Areas Inspected: Special,. announced inspection of high levels of removable radioactivity measured on the. external surface <f a spent fuel cask after-trips between the licensee's facility and Genoa, Wisconsin. The inspection required 22 inspector-hours onsite by one NRC inspector.
Results:
No~ items-of noncompliance were identified.
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i (1108040548 8107227 PDR ADOCK 07001308' 1
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pg a
y DETAILS
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Persons Contacted
- E. E. Voiland, Plant Manager
- K. J. Eger, Senior Engineer, Licensing and Radiological Safety T. E.'Tehan, Senior Engineer, Field Services K. A. Astrom, Field Services Specialist A number of other supervisors, safety technicians, and operating technicians were interviewed.
In addition, representatives of the Dairyland Power Cooperative provided information and data to the inspector.
- Denotes those present at the exit meeting.
2.
General The inspection began at 3:30 p.m. on Sunday, May 31 and was continued on June 5-7, 1981. The purpose of the inspection was to observe activities associated with a series of spent fuel shipments from Morris Operation to the Lacrosse Boiling Water Reactor (LACBWR) at Genoa, Wisconsin. Of special interest and concern were the high levels of j
removable radioactive material detected on the surface of the spent fuel l
cask after three of the seven trips between the two facilitieg.
While contamination levels above the DOT limit of 22,000 dpm/100 cm are not acceptable, such levels do not present a hazard to public health and safety because the cask is enclosed in a metal cage and is therefore inaccessible.
===3.
Background===
i The NAC-1D spent fuel cask is one of a group of identical casks licensed by NRC Certificate of Compliance No. 6698. The official model number or l
cask name is NFS-4.
NAC-1D, the only cask of the NFS-4 group currently in service, has been used for several years to transport spent fuel from reactors to research and fuel storage facilities. The cask has a snooth stainless steel surface and relatively few surface irregularities where radioactive material can lodge to make decontamination difficult after the cask is removed from a fuel storage pool.
The inspector knows of no significant problems of excessive removable radioactivity associated with the NAC-1D cask or with any of the other NFS-4 cas'.s before 1981. There have been occasional reports by licensees, as required by 10 CFR 20.205(b)(2), of localized areas exceeding the DOT limit. There were at least two such reports in 1980 while the cask was in use in Region III.
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-In 1980, the NAC 1D aud.NAC-1E casks.were used alternately in-a' series
~ of fuel transferi rom the ' San Onofre Nuclear Generating Station in" California to Morris. While there was only one report of. removable ~
L surfacelcontamination exceeding the DOT limit, survey data show that'.
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3 removable contamination on the NAC-ID cask was significantly higher.
l than. that on the 1E : cask at the conclusion 'of several of the-eastbound 2-l trips. Contamination levels were generally less-than 2,200 dpm/100 cm i -
when the' casks left California.
When the: fuel shipments from California were congluded, the~NAC-ID cask-l
. was decontaminated to'less than 2,200.dpm/100 cm by Morris Operation,-
l then placed inLoutside storage for about six weeks. Smear surveys made L
in preparation for transferring the empty cask offsite disclosed a general-ingrease in -removable contamination to an average of about 5,000 dpm/}00 -
cm. The cask was again decontaminated to less than 2,200 dpm/100 cm and released for use by other licensees.
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'In-February 1981, the existence of removable' contamination well'above j.
the. DOT limit was reported to NRC on receipt of NAC-1D at; the Oyster Creek Nuclear Station. Before releasing the cask from Oyster Creek, a-
-removable' coating was applied to the. stainless steel surface, apparently l
as a precaution to prevent an increase in removable contamination'during I
transp,rt. Surface-contamination levels were well within the' DOT limit l
when the cask arrived at Battelle Columbus: Laboratories, where the cask l-remained for several weeks. The lic ee applied a' removable coating-
- before immersing the cask in the storage pool to facilitate decontamina-tion and avoid possible problems with meeting the DOT limit. The li--
censee reported that a tendency for removable contamination levels to increase with time was observed during its several weeks at Battelle.
After a final decontamination, the cask was transferred to Morris Operation for use in transporting spent fuel to LACBWR. According to licensee personnel, no surface contamination problems were encountered l
daring this trip.
Attachment A is a tabulation of surface-contamination measured on casks NAC-ID and NAC-1E during the series of' fuel shipments from San Onofre to the licensee in 1980. While not in use, cash ID was stored at the licensee's facility. Late in the year, the cask was transferred to Duke Power Company. Cask 1E was transferred to the Connecticut Yankee Nuclear Station in April 1980 and was not used again in the San Onofre fuel shipments.
i 4.
Removable Contamination During Fuel Shipments to LACBWR The NAC-ID cask was used to transport eight fuel assemblies from Morris to LACBWR, two assemblies at a time.
Seven trips between the two facilities were required after which the empty cask was shipped to Battelle Columbus Laboratories for other use. The purpose of the shipments was to return to LACBWR the eight assemblies which were sent to Morris Operation in 1979 for temporary storage to provide needed space at LACBWR for reracking'of the fuel storage! pool.
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Attachment B is a tabulation-of' removable-contamination measured on
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Ethe cask surface. after.each of the 'seven trips. As indicated,-no levels--
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Jabove the'D1T. limit.of'22,000'dpa/100 cm _were detected after the first two' trips,t.lthough contamination measured by the receiver generally exceeded that measured by'the shipper. -This was not considered unusual based on experience with the cask'during 1980.
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- LACBWR reported removable contamination.above the DOT limit at the t-l conclusion f_the third shipment..The maximum level.of-380,000 2
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dpm/100 cm 'and'an average of about 80,000 dpm/100 cm i exceeded. levels-l previously reported to: Region III' for any spent fuel cask. The receiver stated that decontamination. procedures would be exceptionally thorough.
and would include the-use :of-additional decontamination agents acetone -
and an ammonia solution. These measures appeared successful-in reducing the high contamination ~1evels, and'the empty _ cask was returned'to Morris.
Despite the extensive' decontamination efforts, removable contamination.
again exceeded the DOT-limit after the fourth trip. The.licegsee,after decontaminating the cask surface to less than 1000 dpm/100 cm, subjected the cask to a simulated rainstorm and had the loaded cask onsite for a period corresponding to che transport time between Morris and LACBWR at the request of Region III. When no increase in removable' contamination was detected after eight hours, the cask was allowed to pr( ceed to LACBWR.
When removable contamination levels after the fourth shipment were found
.to exceed those previously encountered, Region III issued an Immediate Action Letter (IAL) to Dairyland Power Cooperative to ensure that the-
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cask remain onsite at LACBWR until positive. actions could be taken that would ensure that the DOT limit would not again be excea6d. The remov-l.
able contamination levels seemed to be affected by mois.. ire, time,.and f}
road vibration.
In response to the IAL, a temporary anendment to the cask certificate was obtained permitting the cask to be covered with' plastic. After decontamination to less than the DOT _ limit, a cover.of-reinforced polyethylene plastic was fitted over the entire cask surface.
As an additional precaution Dairyland agreed to provide a chase vehicle L
equipped with radiation monitoring equipment and materials to make any necessary repairs to the plastic cover during t' trip. The plastic remained intact during the sixth trip, a.M no removable enntamination was detected on the outer surface of the. astir at Morris.
Contamina-tionlevelsonthecasgsurfaceundertheplasticweregenerallyless than 22,000' dpm/100 cm, although. they were higher tb m the levels -
measured bgfore shipment. Contamination in a small area exceeded 22,000 dpm/100 cm apparently because a small amount of contaminated water trapped in a drain port leaked to the surface during transit.
i The cask was again covered with plastic for the final fuel shipment l
to LACBWR. There was no radioactivity on the plastic at the conclusion
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l-of the trip. Contamination levels beneath the plastic were within the l
limit-but slightly above those measured before shipment. L
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5.
Cause of Removable Contamination The licensees involved in the fuel shipments from Morris to LACBWR provided the inspector with measurement data and information that they accumulated in their efforts to quantify and determine the cause,f the removable contamination.
Morris Operation has used casks of the NFS-4 type, including the NAC-1D cask, for several years with no removable contamination problems. The casks have a smooth stainless steel surface which make them relatively easy to decontaminate compared to other types of casks that have been used in the past. Water solutions of a mild detergent, such as trisodium phosphate, had been sufficient to reduce removable contamination levels 2
to less than 22,000 dgm/100 cm and to maintain the level at less than the 22,000 dpm/100 cm DOT limit in subsequent transport. The use of wire brushes and vigorous scrubbing had not been necessary.
The substantial increases in the removable contamination levels on the surface of the NAC-ID cask in late 1980 could indicate a change in the stainless steel cask surface, making removal of radioactive material adhering to the surface more difficult (See Attachment A).
A report 2
in February 1981 of several areas exceeding 80,000 dpm/100 cm detected on receipt of the cask, and a subsequent report that removable contamin-ation tended to increase with time dter decontamination, appear to indicate that normal decontaminatic 1 procedures could no longer reliably control contamination levels withi: che DOT limit. However, the cask was subsequently transported to Morris Operation and then made two trips bet-ween Morris and LACBWR without exceeding the limit. Explanations for this f consistant behavior have not been found.
After ga a 2_ aigh levels of removable contamination were detected following the third trip between Morris and LACBWR, the licensees made measurements to identify and quantify the surface contamination.
Gamma isotopic measurements of the removable contamination disclosed that over 98 percent of the contamination was cesium-134 and cesium-137, with the remainder cobalt-60.
Cesiums and cobalt are the principal radio-nuclides oresent in spent fuel pool water.
In most pools, however, cesiums aad cobalt are present in about equal concentrations.
The licensee made many measurements of the beta activity at the surface of the cask using hand-held ion chamber instruments. Beta activity measurements appear to be proportional to the total quantity of contam-ination on the cask surface, both removable and fixed. On arrival of the third fuel shipment at LACBWR, the shipment disclosing the highest removabl.e contamination levels, the receiver reported beta activity levels in the cask surface averaging 400-500 mrad /hp. This was conserv-atively estimated to represent about 6E6 dpm/100 cm of total fixed and removable activity. Following three decontamination efforts using solutions of potassium permanganate-potassium hydroxide and ammonium citrate oxalic acid, the beta level was reduced to about 40-100 mrad /hr.
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Althoughithis. represents a fivefold to tenfold reduction in. total' surface,
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-activity, the. amount remaining world appear sufficient to exceed the DOT limit:if all the fixed contamiaation were converted to removable contamin-
.ation.
L 6.
Ehit-Interview TheLinanector discussed the_ removable contamination problem with licensee-I representatives identified in Section 1.at the conclusion'of1this' inspection..
JThe' license. representatives said they believed the radioactivity on the-l' cask surface to be an accumulation from various' spent' fuel pools. 1They t
did not'know what causes this mostly fixed contamination to sometimes
-become removable.
The licensee agreed with the.inspectorithat the cask surface may have been affected, perhaps by the'use of strong chemicals, so that caly strong chemicals.are effective-in decontamination.- They-pointed out, however,.that mild detergent solutions had been effective in tne past for_ decontaminating the NAC-ID and other casks. They said they would l-not want to use strong acids, potassium hydroxide potassium permanganate solutions, caustic solutions, or other strong chemicals routinely because these solutions. create a waste handling problem and are~a personnel hazard.-
Attachments:
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Attachment A, Removable Contamination.
on NAC Casks Arriving at Morris 2.
Attachment B, Removable Contamination on NAC-1D Cask During Fuel Transfers to LACBWR-l l
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.! Attachment 1.'
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-Removable Contamination on.NAC; Casks Arriving at Morris.- 1980-D Maximum
-Average Date
-Cask' dpm/100 cm -
dpm/100 cm2.
2 q
'19,000 9,000~
1/21/80 1D 1/22/80-1E
<2,200
<1,000-
- 1/29/80' 1D 8,000 4,000 l
.. 2/15/80 1E
<2,"100
<1,000
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2,'18/80 1D 3,400 1.200
~ 2/27/80
.1E
<2,200
<1,000-l 2/27/80 1D 4,200 1,500-3/6/80.
1E
<2,200
<1,000 3/8/80
-1D 3,100 1,400.
3/15/80 lE 3,000 1,100 3/16/80; 1D
<2,200
<1,000' 3/22/80-1E 7,000 2,000 3/24/80 1D 5,500 2,000 l
8/12/80
-1D 35,000
.10,000 8/25/80 1D 39,000 8,000 9/7/80 1D-21,000 7,000 l:
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Attachment:
B.
. Removable Contamination on'NAC-lD Cask During Fuel Transfers to LACBWR l
' Maximum
~~ Average 2-2 Date dpm/100 cm dpm/100 cm
'1,000 Depart Morris-
,5/26/81
<2,200 5/27/81 8,200-
-3,400 Arrive.LACBWR 5/28/81
<2,200
<1,000 Depart LACBWR 5/28/81:
.11,000 5,000 Arrive Morris 3/29/81
' <2,200'
<1,000 Depart Morris
<5/29/81.
380,000 80,000
. Arrive LACBWR 5/30/81
<2,200
<1,000 Depart LACBWR 5/31/81 280,000 50,000 Arrive Morris 6/2/81
<2,200
<1,000
~ Depart-Morris 6/2/81 2,200,000 1,000,000
. Arrive LACBWR 6/3/81
- Zero (<2,200)-
- *Zero (<1,000)
- Depart LACBWR 6/5/81
- Zero (31,000)-
- Zero (5,000)
Arrive Merris 6/7/81
- Zero (<2,200)
- Zero:(<1,000)
Depart Morrin-
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6/7/81
- Zero.(7,000)
- Zero (2,000)
Arrive'LACBWR I
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- Zero on surface of plastic cover.
Parenthetical Numbers are Contamination Under Cover.
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