Corrosion of austenitic stainless steel alloys due to HNO$sub 3$--HF mixtures

Abstract

T h i s r e p o r t was p r e p a r e d a s a n a c c o u n t o f w o r k s p o n s o r e d by t h e U n i t e d S t a t e s G o v e r n m e n t . N e i t h e r t h e U n i t e d S t a t e s n o r t h e U n i t e d S t a t e s A t o m i cE n e r g y C o m m i s s i o n , n o r a n y o f t h e i r e m p l o y e e s , n o r a n y o f t h e i r c o n t r a c t o r s , s u b c o n t r a c t o r s , o r t h e i r e m p l o y e e s , makes a n y w a r r a n t y , e x p r e s s or i m p l i e d , o r assumes a n y l e g a 7 I i a b i I i t y o r r e s p o n s i b i I i t y f o r t h e a c c u r a c y , c o m p l e t en e s s o r u s e f u l n e s s o f a n y i n f o r m a t i o n , a p p a r a t u s , p r o d u c t o r p r o z e s s d i sc l o s e d , o r r e p r e s e n t s t h a t i t s u s e w o u l d n o t i n f r i n g e p r i v a t e l y owned r i g h t s . DISCLAIMER €I. S. Cole N O T I C EThis report was prepared as an account of work sponsored by the United States Government. Neither the United States nor the United States Atomic Energy Commission, cor a n j of their empioyees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness or usefulness of any information, apparatus, product or process disclosed, or represents that its use would not infringe privately owned rights. ALLIED CHEMICAL CORPORATION IDAHO CHEMICAL PROGRAMS-OPERATIONS OFFICE ABSTRACTThis report represents a literature survey, plus some experimental work, on the corrosion of austenitic stainless steel alloys due to HN03-HF mixtures. Most of the available data were obtained during the processing of spent nuclear fuel elements where solutions containing nitrates and fluorides are frequently encountered. Austenitic stainless steels have been extensively used in nitrate-fluoride solution service in these plants. It has been shown that their service may be improved by: (1) proper annealing; (2) stabilizing with columbium (niobium) or titanium; ( 3 ) complexing the solutions the stainless steels will contain with aluminum, zirconium, or thorium; (4) utilizing stainless steels which have a low carbon content; ( 5 ) maintaining the uncomplexed hydrofluoric acid in the solution at as low a value as practicable; and (6) utilizing neutron absorbing elements in the alloys at concentrations as low as possible for service as fixed nuclear poisons. Other protective measures such as reduced contact time, temperature, concentration, and fluoride-to-nitrate ratio can be employed to minimize corrosion. n ..

Dissolution of Zirconium-Bonded, Monolithic, Uranium-Molybdenum Fuel for Uranium Recovery

“…Similar rates (~25 to 100 mils/yr) were observed in the Thorex reprocessing at Oak Ridge (English [1959(English [ , 1960, as cited by Cole [1974]). Very high corrosion rates (>>100 mils/yr) are observed for 316 stainless steel in solutions containing only HF with no nitric or available complexants (Osborn et al 2002) and for 300-series stainless steels in nitric/HF mixtures containing no complexants (Cole 1974), although the role of complexants in decreasing the corrosion rates, often by orders of magnitude, is acknowledged (Cole 1974). The role of aluminum complexants was studied separately in a brief report by Walker (1957), where 2-M nitric/1 M-hydrofluoric solutions obtained corrosion rates spanning from ~17mils/yr to over 12,000 mils/yr, depending upon the concentration of added aluminum.…”

“…In a proposed thoria/urania dissolver solution consisting of 12-M nitric acid with 0.05-M hydrofluoric acid (initial) plus 0.025-M dissolved zirconium, the corrosion rate of 304L stainless steel was reduced to 13 mils/year (Ondrejcin and McLaughlin 1980). Similar rates (~25 to 100 mils/yr) were observed in the Thorex reprocessing at Oak Ridge (English [1959(English [ , 1960, as cited by Cole [1974]). Very high corrosion rates (>>100 mils/yr) are observed for 316 stainless steel in solutions containing only HF with no nitric or available complexants (Osborn et al 2002) and for 300-series stainless steels in nitric/HF mixtures containing no complexants (Cole 1974), although the role of complexants in decreasing the corrosion rates, often by orders of magnitude, is acknowledged (Cole 1974).…”

“…The role of aluminum complexants was studied separately in a brief report by Walker (1957), where 2-M nitric/1 M-hydrofluoric solutions obtained corrosion rates spanning from ~17mils/yr to over 12,000 mils/yr, depending upon the concentration of added aluminum. Although not as widely studied, the corrosion rate in the vapor above the nitric/ hydrofluoric acid solutions has been noted and is generally higher by a factor of less than 3 (Cole 1974).…”

Advanced evaporator technology progress report FY 1992

“…Barnov et al [BARNOV] investigated the vapor-liquid equilibria of 13 nitric acidwater-nitrate salt systems at atmospheric pressure. Nitrate salts included potassium, sodium, lithium, -1974- , EFIMOV-1975. The plot is shown in Fig.…”

Korrosion nichtrostender Stähle und Nickelbasislegierungen in Salpetersäure‐Flußsäure‐Gemischen

“…S Cole[29] steigt der Angriff auf X 2 CrNi 19 11, Werkst.-Nr. Die scheinbaren Aktivierungsenergien EA sind von der FluWsaure-Konzentraition nahezu unabhangig und betragen -21 bis 42 kJ/mol bei HNOs-Konzentrationen 2 1,3 M und -38 his 59 kJ/mol bei kleineren HN03-Konzentrationen.Nach H .…”