ML19338D536
| ML19338D536 | |
| Person / Time | |
|---|---|
| Site: | Wood River Junction |
| Issue date: | 08/21/1980 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Bowers C UNC RECOVERY SYSTEMS, UNITED NUCLEAR CORP. (SUBS. OF UNC, INC.) |
| References | |
| NUDOCS 8009230413 | |
| Download: ML19338D536 (4) | |
Text
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-[.- #g UNITED STATES H
. NUCLEAR REGULATORY COMMISSION
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I REGION I '
8 631 PARK AVENUE 4
KING OF PRUS$6A, PENNSYLVANIA 19406 August 21, 1980
. Docket No.70-820
-United Nuclear Corporation
. ATTN: Mr. C. E. Bowers President'
. UNC Recovery Systems -
Wood River Junction, Rhode Island. 02854 4
e Gentlemen:
The enclosed IE Circular No. 80-20, " Changes In Safe-Slab Tank Dimensions," is-forwarded to you for information.
No written response is required.
If you desire additional information regarding this matter, please contact this office.
Sincerely, ww#4. A B
e H. Grier rector
Enclosures:
1.
IE Circular No. 80-20 2.
List of Recently Issued IE Circulars CONTACT: - H. W. Crocker (215-337-5217)
-cc w/encis:
R. J. Gregg, Manager, Quality Assurance r
D. M. Schultz, Manager, Compliance i
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.IEC 80-20 UNITED STATES 1NUCLkAR REGULATORY COMISSION-OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON,' D.C.
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August 21, 1980 I
IE Circular No. 80-20:
CHANGES IN SAFE-SLAB TANK DIMENSIONS DescriptionofCircumstances:!;,
~
Duringaroutineinspectionat'a.fueljfacility,anNRCinspectorreceiveda report of significant dimensional changes in safe geometry tanks.
The. tanks were used to. store low-enriche'd uranium. solutions from a scrap dissolver.
The problem was first identified' shen a ~ sight glass mounted on the large face of one of three safe-slib tanks cracked from the strain of tank dimensional ff 2
changes.
Further investigation and measurements revealed that the large faces of two of the tanks had bulged and increased the thickness dimensions of the
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tanks.
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The maximum bulge occurred at the center of one of the tanks, increasing the tank thickness 2 1/2 in.,beyond the design thickness of 5 1/2 in., The bulge tapered from the tank centers to.the-designed 5 1/2 in. at the tank edges.
The tanks were.made of 1/8-in. type 304 stainless steel with the tank edges and large faces supported and ' stiffened by 3/16-in. angle iron.
i The cause of the bulging was believed to be overpressurization due to partial
. i plu'gging of the tank vent lines.
Contributing factors may:have been excessive transfer rates, metal fatigue ~ aggravated by corrosion, and the high specific gravity of the stored solution.
Replacement tanks were provided with tie-bars and heavier 1/4-in. angle iron
-stiffeners to preserve the thickness dimensions.
Conservative calculations, taking into account the weight of solution, tank dimensions, and tie-bar and stiffener strength, indicated'that' required dimensions would be maintained.
A precondition for the calculations required t' hat the tank vent system be i
designed.to prevent accidental pressurization.
To prevent accidentaiLpressurization, a 1-1/2-in. overflow line was connected to the 1-1/2-in. vent line to the process offgas (POG) system at a' point r
f immediately above each tank.,This provided a positive overflow as well-as a second vent in. case a plug occufre'd in the main-POG line.
Additionally, each tank wts provided with a 2" x 4" inspection port at the top with a cover free to'" float", should pressurization occur.
I The tank dimensions ~were approximately 62" x 62" x 5 1/2".
The tank locations were parallel to and about 1 ft removed from the scrap recovery area walls.
The visual detection of.the 2-1/2-in. deficction of the large tank face from a a
point ~in front ~of.the tank is usually difficult u that measurements should be made with calipers or'similar equipment to assure detection of significant distortion.
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IEC 80-20 August 21,-1980 Pago 2 of.2 L
Notice to Licensees:
All-licensees using safe-slab tanks should be aware of the possible changes in tank dimensions resulting from hydraulic or pneumatic forces.
Certain steps should be taken to prevent or detect changes in safe-slab tank dimensions.
~These actions include the following:
(1) Structural analyses should be reviewed for all vessels designed to be geometrically safe to assure that the possibility of pressurization has been adequately considered.
The use of tie-bars and rigid steel supports should be considered in designs for new tanks.
(2) The possibility of. vent lines becoming plugged should be studied and special overflow mechanisms should be provided if pressurization by vent line plugging is possible.
(3) Provision should be made for routine dimensional checks of geometrically safe. vessels.
These checks should be made whether or not the vessels are subject to pressurization.
No written response to this circular is required.
If additional information regarding this subject is required, contact the Director of this office.
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IE Circular 80-20 Enc 1:sure'2 August 21, 1980
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