ML19338D526

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

ML19338D526
Person / Time
Site:	07001201
Issue date:	08/21/1980
From:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
To:	Heer W BABCOCK & WILCOX CO.
References
NUDOCS 8009230398
Download: ML19338D526 (4)

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UNITED STATES 8

NUCLEAR REGULATORY COMMISSION o

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REGION 11

'04 g-101 MARIETTA ST., N.W., SUITE 3100

' ATLANTA, GEORGIA 30303 g***** g AUG 21 isso

In' Reply Refer To Babcock.and Wilcox Company '

-ATTN: Mr. W. F. Heer, Manager Virginia Operations, Nuclear Materials and Manufacturing Division Cominercial Nuclear Fuel Plant i

P. O. Box 800 Lynchburg, VA 24505 Gentlemen:

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

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

Sincerely,

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James P. O'Reilly Director

Enclosures:

1.

IE Circular No. 80-20 2.

List of Recently Issued IE Circulars 1

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IEC 80-20

UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT D

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WASHINGTON,'D.C. 20555 3g g

August 21,- 1980-IE Circular No. 80-20: ; CHANGES IN SAFE-SLAB TANK DIMENSIONS

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. Description of Circumstancesh i

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 ide'ntified~when a sight-glass mounted on the large face of i\\

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 maximun' 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.t 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

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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 required dimensions would be maintained. A

. precondition for the calculations required that-the tank vent system be designed to prevent accidental pressurization.

t To prevent accidental pressurization, a 1-1/2-in. overflow line was connected E

to the 1-1/2-in. vent line to the process offgas (POG) 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.

The tank dimensions were approximately 62" x 62" x 5 1/2".

The tank locations were: parallel Lto 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 i

distortion.

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-IEC 80-20 Auguot 21, 1980 Page 2 of 2 4-

Notice to Licensees:

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' 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 prepeurization has been adequately considered. The use of tie-bars and rigid steel supports should be considered in designs'for new tanks.

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(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 ubject 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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6 IEC 80-20 August;21, 1980' s:

- RECENTLY ISSUED IE-CIRCULARS

' Circular Date of

.No.

Subject Issue Issued to

.80-20

. Changes in Safe-Slab 8/21/80 All Part 50 and'Part Tank Dimensions 70 Fuel Facility Licensees 80-19 Noncompliance 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 Evaluations for Changes to facilities with an Radioactive Waste Treatment OL or CP

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Systems 80-17

' Fuel Pin-Damage-Due to Water 7/23/80 All holders of PWR Jet from Baffle Plate Corner OLs and PWR cps-80-16

~ Operational-Deficiencies In 6/27/80 All power reactor

'Rosemount Model SIODU Trip facilities with an 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 Natural.Circula-facilities with:an tion Cooldown.

OL or CP i.

80 Radioactive Contamination of 6/24/80 All holders of power Plant Demineralized Water and research reactor Systemiand Resultant Internal licenses (operating i

Contamination of Personnel and construction permits), and fuel-cycle licensees 1

80-13 Grid Strap Damage in 5/18/80 All holders of reactor Westinghouse Fuel' Assemblies OLs and cps

80. Valve-Shaft-To-Actuator Key' 5/14/80 All holders of reactor TMay. Fall Out of Place 54en OLs and cps Mounted Below Horizontal' Axis

' 80-11 Emergency Diesel. Generator 5/13/80 All holdert of a power Lube-Oil Cooler Failures-

-reactor OL ar CP

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180-10'

-Failure to Maintain-4/29/80 All holders of reactor-

' Environmental Qualification OLs and cps of~ Equipment

80-09~

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-Problems;WithLPlant Internal' 4/28/80 All-holders ofia power

. Communications Systems' reactor OL or CP 9

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