ML20024B541
| ML20024B541 | |
| Person / Time | |
|---|---|
| Site: | Wood River Junction |
| Issue date: | 06/06/1983 |
| From: | Helgeson K UNITED NUCLEAR CORP. (SUBS. OF UNC, INC.) |
| To: | Crow W NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| 22349, NISRI:83-041, NISRI:83-41, NUDOCS 8307090102 | |
| Download: ML20024B541 (6) | |
Text
r UnC RECOVERYENSTCms 70 82B PPA' W /I auss' Division of Uniteo Nucleae Corporat:on One Narragansett Trail Telephone 401/364-7701 g
A Unc RESOURCd5 Company Wood R.ver Junction. Rhode istand 02894 NISRI: 83-041 June 6,
1983 so 5
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United States Nuclear Docgg 9
i Regulatory Commission
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usage Office of Nuclear Material C
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Safety and Safeguards Z;
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- WS Mr. W. T.
Crow, Section Leader k]Sy%
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Wilste Building g
7915 Eastern Avenue, Silver Spring, MD 20910 f>
Gentlemen:
Based on assumptions and survey data described in the attachment to this letter, UNC Recovery Systems requests that the third floor ceiling of the Columns Tower at this facility be released for unrestricted use (at the time the rest of the building is released), based on appli-cation of the ALARA concept to those areas containing residual contamination in excess of NRC decontamination guidelines.
If there are any questions concerning this matter, do not hesitate to contact the writer.
Very truly yours, UNC Recovery Systems K. A. Helg Manager, Qua Ity Assurance and Nuclear and Industrial Safety o
cfg R. J. Gregg, UNC, w/attachmeriE
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Roth, USNRC, w/ attachment i 2
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ATTACHMENT, NISRI: 83-041 1
The third floor ceiling of the Columns Tower is a poured concrete slab approximately 25' x 25' x 5". thick with steel reinforcing.
Poured integrally with this slab is an eight inch thick support pad for the 20,000 gallon water tank, on the roof, which provides domestic and fire protection water for the facility.
Evidently, when this slab was poured, no great effort was made to vibrate the wet concrete to disentrain air bubbles from the face cf the form.
Consequently, there are numerous small cavities on the face of the ceiling slab caused by air bubbles.
When th'e building was constructed and during it's operating life, no at-tempt was made to protect the surface of this ceiling slab by painting or otherwise sealing the concrete surface.
During the incident in 1964, an area of approximately 100 square feet, immediately above the mixing vessel involved in the inci-dent, was splashed with pregnant liquor.
Subsequently, the areas involved in the incident were decontaminated by washing.
Although the radioactivity levels were significantly reduced, there re-mained some contamination absorbed in the concrete and in the small surface cavities.
During decontamination efforts in 1981 and 1982, the entire third floor of the Column Tower was grit blasted several times to re-move residual contamination.
While the efforts expended on the ceiling reduced the contamination levels, they did not bring the complete surface down to, or below, the NRC release criteria limits.
UNC is requesting permission to invoke the ALARA concept in rela-tion to the third floor ceiling contaminated area, as we feel we have expended every reasonable effort in decontamination of this area and that the remaining contamination would present no un-reasonable risk or hazard to the general public.
To accomplish additional decontamination would necessitate compromising the structural integrity of this slab which supports approximately 167,000 pounds of water plus the weight of the supply tank.
The following information contains survey data for the present con-dition of the ceiling slab, possible beta-gamma exposure data, and estimated exposures of personnel involved in possible future uses of this area.
PHYSICAL DESCRIPTION OF ROOM:
Floor area:
Approximately 25 feet by 18 feet or 450 square feet is exposed to the ceiling area in question.
This ignores two openings in the floor totalling 133 square feet.
The floor is a poured con-crete slab.
Wall area:
The wall height, approximately twelve feet,
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floor to ceiling, is composed of hollow con-l crete blocks.
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Structural steel:
The floor and ceiling are supported by steel members, structurally supported by steel verti-cal members.
The walls are non-supporting.
Of the total number of survey grid blocks (36' x 36') encompass-ing the ceiling (72 blocks), ORAU's survey, in April, 1983, re-jected nine blocks.
Five blocks were rejected for alpha contam-ination alone and four blocks were rejected for both alpha and beta-gamma contamination.
ORAU survey results of the rejected blocks are shown below in dpm/100 cm2, alpha max.
alpha avg.
beta max.,
beta avg.
CC-4 23,472 8,880
-5 15,240 8,277
-6 59,232 28,704 16,576 11,950
-7 31,608 26,006 14,840 11,312
-8 30,864 17,294 11,592 7,134
-14 26,040 12,666
-15 26,352 9,846 9,968 5,138
-16 28,104 7,188
-22 21,240 9,932 NRC Limit: 15,000 5,000 15,000 5,000 The other grid blocks were presumably within the criteria limits, although UNC does not have the ORAU results for them.
UNC survey results show that these blocks meet the NRC limits.
Gamma readings are as shown below:
Max.
Avg.
One meter from floor surface:
20 pR/hr 17 pR/hr One meter from ceiling surface:
24 pR/hr 17 pR/hr Two Meters from floor surface:
23 pR/hr 16 pR/hr As the ceiling of this room is approximately 12 feet above the floor level, it is very unlikely that any occupant of the room would come within three feet of the ceiling for a protracted period of time during any postulated use of this room.
It could be postulated that a person could sit or stand for approximately seven hours per day for five days per week during the occupation of this room in the event that this area was used as an office or working area.
If this were the case, a person's exposure would be approximately:
STANDING:
max max max exp. rate exp./ day exp./ week 23 pR/hr 161 pR 805 pR avg avg avg exp. rate exp./ day exp./ week 16 pR/hr 112 pR 560 pR SITTING:
max max max exp. rate exp./ day exp./ week 20 pR/hr 140 pR 700 pR avg avg avg exp. rate exp./ day exp./ week 17 pR/hr 11.9 pR 595 pR 4
4 Assuming a 50 week work year, the yearly exposures would only be:
' STANDING:
max. exp./yr avg. exp./yr o
40 mrem /yr 28 mrem /yr SITTING:
35 mrem /yr 30 mrem /yr As a comparison, the limits set forth for the exposure to person-r l
nel in unrestricted areas is shown below.
The limits are taken from 10 CFR 20, paragraphs 20.101 (a), 20.105 (a), and 20.105 (b) (1) (2).
. Personnel Max. Exp. Limits 0.5 rem /yr (500 mrem) 2.0 mrem /hr 100 mrem in seven consecutive day period.
~That a person would -sit-or stand in this room for the period of time assumed is extremely unlikely.
Therefore, these figures are worst case suppositions.
Smear surveys show little or no transferrabic contamination on the surface of the' ceiling concrete.
As there is no traffic, no sig-nificant " dusting"~could be expected to occur'and therefore, no
" tramp" or airborne. contamination should be present in this room.
Below are_shown the. maximum smear levels determined during UNC's survey of the area.
Max. Smear Levels (dpm/100 cm2)
Avg. Alpha Max.1 Alpha 1.0 1.0 7.0 i 2.6
...m.
Avg. Beta Max. Beta 3.0 1.7 16.0 4.0 Possible:uses to which this room'may be subjected and the exposure consequences arising from these uses are discussed below.
1.
STORAGE AREA As a storage area, the room would have little or minimal traf-fic and personnel entering or leaving the area would not be exposed to significant levels of residual radiation or contan-ination.
As the levels of transferrable contamination are ex-tremely low, as shown above, the possibility of stored mat-erial~becoming contaminated is very remote.
2.
. OFFICE / WORK AREA As described earlier, there would be no significant exposure i-to penetrating radiation of-personnel occupying this room as an office or work area.
In order to use this room, due to the
. decontamination methods, the floor will have to be resurfaced in order to allow its use.as an office or work area.,
r As an office / work area, the interior would be painted, again sealing off any residual contamination.
For an office, the ob-vious treatment for the ceiling would be a drop ceiling (prefer-able) or painting.
The drop ceiling would isolate the ceiling from the rest of the room and painting would seal any residual contamination into the pores of the concretc.
In either case, there could be no significant exposure to room occupants.
3.
DEMOLITION OF 3rd. FLOOR CEILING SLAB Deinolition will not be considered as a likely supposition as this slab provides the support for the facility's water supply tank.
Without this tank, there is no fire protection water.
This would prove unacceptable to the insurance carrier.
An auxilliary water supply system would have to be purchased and installed to provide drinking water, sanitary water, and feed water for the facility boiler.
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'" LICENSE' AMENDMENTS" i
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William O. Miller, License Fee Management Branch, ADM
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MATERIALS LICENSE AMENDMENT CLASSIFICATION sw'Ew
. r.:a Applicant:
(/ d)O License No:
544-777 Fee. Category:
6h Application Dated:
4M F3 Received:
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Applicant!s Classification:'
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The above application for amendment has been reviewed by NMSS in h
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accordance with S170.31 of part 170, and is classified as follows:
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Safety and Environmental Amendments to Licenses in Fee Categories 1A throuch'1H,'2A, 28, 2C, and 4A xn l'Y.Ili (a)
Major safety and environmental
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(b) hinor safety and environmental (c)
Safety and environmental (Categories ID through 1G only)
(d)
Administrative' 2
Justification for reclassification:
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The application was filed (a) cursuant to written NRC request and the amendment is being issued for the convenience of the Commission, or (b)
A ther (State reason):
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Division of Fuel Cycle & Material Safety l 'i'$k Date
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