ML19338B958
| ML19338B958 | |
| Person / Time | |
|---|---|
| Site: | 05000000 |
| Issue date: | 08/21/1980 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| To: | |
| References | |
| REF-SSINS-6830 IEC-80-20, NUDOCS 8006190036 | |
| Download: ML19338B958 (3) | |
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4 SSINS: 6830 Accession No.:
8006190036 IEC 80-20 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE-OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 August 21, 1980 4
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 ircreased 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 51/2 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 pluggirg of the tank vent lines. Contributing factors may have been excessive trans'er 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 i
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, j
_To prevent accidental pressurizat en, a 1-1/2-in. overflow line was connected i
to the 1-1/2-in. vent line to the process offgas (POG) system at a point intnediately above each tank. This provided a positive overflow as well as a 1
second vent in case a plug occurred in the main POG 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
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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 August 21, 1980 Page 2 of 2 Notice to Licensees:
All licensees using safe-slab tanks should be aware of the possible changes in tank dimensions resulting frem' 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 oossibility of vent lines beccming 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 'o this circular is required.
If additional information regarding this subje.Lis required, contact the Director of this office.
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IEC 80-20 August 21, 1980 RECENTLY ISSUED IE CIRCULARS Circular Date of No.
Subject Issue Issued to 30-19 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 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 51000 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 80-14 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 80-13 Grid Strap Damage in 5/18/80 All holders of reactor Westinghouse Fuel Assemblies Ols and cps 80-12 Valve-Shaft-To-Actuator Key 5/14/80 All holders of reactor 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 80 Failure.to Maintain 4/29/80 All holders of reactor Environmental Qualification OLs and cps
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of Equipment 80-09 Problems With Plant Internal 4/28/80 All holders of a power Communications Systems reactor OL or CP
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