241-AY-101 Tank Construction Extent of Condition Review for Tank Integrity

Abstract

This report provides the results of an extent of condition construction history review for tank 241-AY-101. The construction history of tank 241-AY-101 has been reviewed to identify issues similar to those experienced during tank AY-102 construction. Those issues and others impacting integrity are discussed based on information found in available construction records, using tank AY-102 as the comparison benchmark. In tank 241-AY-101, the second double-shell tank constructed, similar issues as those with tank 241-AY-102 construction reoccurred. The overall extent of similary and affect on tank 241-AY-101 integrity is described herein. EXECUTIVE SUMMARYThe construction history of the 241-AY-101 (AY-101) tank has been reviewed to identify any concerns for the long-term integrity of the tank. This initial review was prompted by construction issues identified during the formal leak assessment for tank 241-AY-102 (AY-102), RPP-ASMT-53793, Tank 241-AY-102 Leak Assessment Report. In tank AY-102, bulges in the secondary liner, deterioration of refractory during post-weld stress relieving (post-weld heat treatment), and primary tank floor plate welding rework during construction left residual stresses in the tank that may have accelerated corrosion and contributed to the primary tank failure. The main purpose of this review was to determine whether construction modifications made between tanks AY-102 and AY-101 either improved the integrity of tank AY-101 or produced similar reduced margins.During construction of the 241-AY tank farm, the most significant deficiency found in the review was the degradation and repair of the refractory in tanks AY-101 and AY-102. Both refractories were exposed to similar conditions of moisture and freezing temperatures during the curing stage, which is believed to have contributed to the friable nature and reduced vertical compressive strength. The refractory repairs required the outer 21 in. of the periphery refractory to be chipped out all the way around the tank and replaced with reinforced structural concrete.Significant problems arose with welding of the secondary liner and primary tank bottoms of tank AY-102 with a weld rejection rate of 33.8%. Welding improved with fabrication of tank AY-101 with a weld rejection of 10.2%. Regarding tank bottom flatness, tank AY-101 had a total of six instances of secondary liner bottom bulging as compared to tank AY-102 with 22 instances. No QA inspections indicated that bulging of the primary tank bottom occurred in tank AY-101 and the information discovered substantiates that it met specification. Despite this documentation, photos from refractory repair after stress relief indicate that voids existed between the primary tank and refractory surface. These voids could be attributed to primary tank bottom bulges, which would indicate unsupported areas of the primary tank exist in tank AY-101. This lack of support was identified a contributing factor to primary tank failure in tank AY-102.The post-weld stress relieving of tank AY-101 was more successf...