History of waste tank 16, 1959 through 1974

Tank 16 was placed in service as a receiver of fresh high heat waste (HW) on May 9, 1959, and was filled to capacity in May 1960. Approximately half the tank contents were transferred to tanks 14 and 15 during September and October 1960 because of leakage into the annulus. Use of tank 16 was resumed in October 1967 when authorization (TA 2-603) was obtained to receive LW, and the tank was filled to capacity by June 1968. Subsequently, supernate was removed from the tank, and a blend of fresh LW and evaporator bottoms was added. In March 1972, the supernate was transferred to tank 13 because leakage had resumed. The sludge was left in the tank bottom and the use of tank 16 for any additional waste storage was discontinued. In September 1960 liquid waste overflowed the annulus pan. Leakage essentially stopped after the tank liquid level was lowered below the middle horizontal weld. After exhaustive study, tank cracking and resultant leakage was concluded to have been caused by stress corrosion due to the action of NaOH or NaNO3 on areas of high local stress in the steel plate such as welds. Samples of sludge, supernate, tank vapors, and leaked material in the annulus were analyzed, and tank temperature and radiation profiles were taken. Two disk samples were cut from the primary tank wall for metallurgical examination. Test coupons of various metals were exposed to tank 16 waste to aid new tank design and to study stress corrosion and hydrogen embrittlement. In addition, samples of SRP bedrock were placed in tank 16 to study reactions between bedrock and HW. 18 figures, 2 tables