ML19338D507

Forwards IE Circular 80-20, Changes in Safe-Slab Tank Dimensions. No Written Response Required

ML19338D507
Person / Time
Site:	07000754, 07001007
Issue date:	08/21/1980
From:	Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
To:	Darmitzel R GENERAL ELECTRIC CO.
References
NUDOCS 8009230370
Download: ML19338D507 (4)

Text

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NUCLEAR REGULATORY COMMISSION -

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1990 N. CALIFORNIA ROULEVARD D

SUITE 202. WALNUT CREEK PLAZA

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• e e, *,o WALNUT CR EE K, CALIFORNIA 94596 August 21, 1980' Docket Nos..70-754,'70-1007 General Electric Company Vallecitos Nuclear Center Vallecitos Road Pleasanton, CA 94566 Attention: Mr. R. W. Darmitzel, Manager, Irradiation Processing Operation dentlenen:

The enclosed IE Circular No. 80-20 is forwarded for your information.

If-there are any questions related to-the suggested actions, please contact this office.

Sincerely,

/ dw (f-c R. H. Engelken Director EP::losures:

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IE Circular No. 80-20 2.

Recently issued IE Circulars s

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SSIllS: 6830 Accession No.:

8006190036 IEC 80-20 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT g

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a August 21, 1980 IE Circular No. 80-20: CHANGES IN SAFE-SLAB TANK DIMENSIONS Description of. Circumstances:

During a routine inspection at a fuel facility, an NRC inspector received a report.of significant dimensional changes in safe geometry tanks. The tanks were used to store low-enriched uranium solutions from a scrap dissolver. The problem was first identified when a sight-glass mounted on the large face of one of three safe-slab tanks cracked from the strain of tank dimensional changes.

Further investigation and measurements' revealed that the large' faces of two of the tanks had bulged and increased the thickness dimensions of the tanks.

The maximum bulge occurred at the center of one of the tanks, increasing the tank thickness 21/2 in. beyond the design thickness of 51/2 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.

The cause of the bulging was believed to be overpressurization due to partial plugging 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 reouired dimensions would be maintained. A precondition for the calculations required that the tank vent system be designed to prevent accidental: pressurization.

To prevent accidental pressurization, a 1-1/?-in. overflow line was connected to the 1-1/2-in. vent line to the process offgas (P0G) system at a point immediately above each tank. This provided a positive overflow as well as a second vent-in case a plug occurred in the main P0G.line. Additionally, each tank was provided with a 2" x 4" inspection port at the top with a cover free to " float" should pressurization occur.-

Theetank 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. deflection of the large-tank face from a point in front of the tank is usually difficult so that measurements should be~

made-with. calipers or similar equipment to assure detection-of significant

. distortion.

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IEC 80-20~

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-August'21, 1980J Page 2 of.2 Notice'to Licensees:

All ~ licensees.using safe-slab -tanks should be_ aware 'of the possible changes in -

tank ' dimensions.resulting from hydraulicior pneumatic. forces.- ~ Certain steps

.should.be taken.to prevent or detect: changes in safe-slab tank dimensions.

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These actions Linclude the following:

(1)' Structural analyses.should be reviewed for all vessels designed to be.

geometrically safe to assure that' thel pos'sibility of pressurization has been' adequately ~ consideredi The use Mf. tie-bars :and rigid steel supports should _be considered-in designs.for new tanks..

~(2)" The possibility of vent lines ~ becoming plugged'shbuld be studied and special' overflow mechanisms should be provided if pressurization by vent-line-plugging is possible.--

(3) Provision sh6uld 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 circula'r is-required.. If additional information regarding this subject is required, contact the Director of this office.

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..IEC 80-20 August 21, 1980 RECEllTLY ISSUED IE CIRCULARS l=

l Circular Date of

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' Subject Issue-Issued to 80-19

- tioncompliance.with -

8/26/80 All medical licensees License Requirements for-

' Medical Licensees 80-18 10.CFR 50.59 Safety.

8/22/80 All power reactor Evtluations for Changes to facilities with an Radioactive Waste Treatment OL or CP I

Systems 80-17.

Fuel Pin Damage Due to Water 7/23/80 All holders of PWR Jetifrom Baffle Plate Corner OLs and PWR cps

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80-16 Operational Deficiencies In 6/27/80 All power reactor Rosemount Mo_ del 510D0 Trip facilities.with an 1

Units And Model 1152 Pressure OL or a CP-

' Transmitters 80-15 Loss of Reactor Coolant Pump 6/20/80 All power reactor Cooling and.tlatural Circula-facilities with an tion Cooldown OL or CP

, 14 Radioactive Contamination of 6/24/80 All holders of power Plant Demineralized Water and research reactor System and Resultant Internal licenses (operating Contamination of' Personnel and construction permits), and fuel cycle licensees 13 Grid Strap Damage in 5/18/80 All holders of reactor Westinghouse Fuel Assemblies OLs and cps 80-12 Valve-Shaf t-To-Actuator Key 5/14/80 All holders of reactor y

May Fall-Out of Place When Ols and cps Mounted Below Horizontal Axis 80-11 Emergency Diesel. Generator.

5/13/80 All holders of a power

. Lube Oil Cooler Failures reactor OL or CP

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. Failure to Maintain 4/29/80 All holders of reactor Environmental-Qualification OLs and cps of Equipment' 09.

Problems With Plant Internal 4/28/80 All holders of a power Communications Systems reactor OL'or CP m'

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