Title: REFERENCE ELECTRODE AND ITS USE IN DETERMINING INDIVIDUAL ELECTRODE POTENTIALS.

The importance of knowing the electrochemical corrosion potential (ECP, also referred to as E{sub con}) of nickel-base alloys in hydrogenated water is related to the need to understand the effects of dissolved (i.e., aqueous) hydrogen concentration ([H{sub 2}]) on primary water stress corrosion cracking (PWSCC). Also, the use of a reference electrode (RE) can improve test quality by heightening the ability to detect instances of out-of-specification or unexpected chemistry. Three methods are used to measure and calculate the ECP of nickel-based alloys in hydrogenated water containing {approx} 1 to 150 scc/kg H{sub 2} (0.1 to 13.6 ppm H{sub 2}) atmore » 260 to 360 C. The three methods are referred to as the specimen/component method, the platinum (Pt) method, and the yttria-stabilized zirconia/iron-iron oxide (YSZ/Fe-Fe{sub 3}O{sub 4}) RE method. The specimen/component method relies upon the assumption that the specimen or component behaves as a hydrogen electrode, and its E{sub corr} is calculated using the Nernst equation. The present work shows that this method is valid for aqueous H{sub 2} levels {ge} {approx} 5 to 10 scc/kg H{sub 2}. The Pt method uses a voltage measurement between the specimen or component and a Pt electrode, with the Pt assumed to behave as a hydrogen electrode; this method is valid as long as the aqueous H{sub 2}level is known. The YSZ/Fe-Fe{sub 3}O{sub 4}, which represents a relatively new approach for measuring E{sub corr} in this environment, can be used even if the aqueous H{sub 2} level is unknown. The electrochemical performance of the YSZ/Fe-Fe{sub 3}O{sub 4} probe supports its viability as a RE for use in high temperature hydrogenated water. Recent design modifications incorporating a teflon sealant have improved the durability of this RE (however, some of the REs do still fail prematurely due to water in-leakage). The Pt method is judged to represent the best overall approach, though there are cases where the other methods are superior. For example, the specimen/component method provides the simplest approach for calculating the E{sub corr} of plant components, and the YSZ/Fe-Fe{sub 3}O{sub 4} RE method provides the best approach if the H{sub 2} level is unknown, or in off-nominal chemistry conditions. The present paper describes the use of these methods to determine the ECP of a specimen or component versus the ECP of the nickel/nickel oxide (Ni/NiO) phase transition, which is important since prior work has shown that this parameter (ECP-ECP{sub Ni/NiO}) can be used to assess aqueous H{sub 2} effects on PWSCC.« less

To test the toxicity of nitrogen dioxide/nitrogen tetraoxide and other gases, it was necessary to construct an exposure chamber for small laboratory animals. This report describes the construction and operation of a small dynamic flow gassing chamber for studying toxic gas inhalation. Special attention is given to its use with NO/sub 2//N/sub 2/O/sub 4/ and the system for monitoring the concentration of gas. Several accessories for the chamber include a special harness for monitoring chest sounds of the subjects being gassed; a system for endotracheal intubation for allowing the subject to breathe the gas concentration while being manipulated surgically outsidemore » the chamber; and, a small by-pass chamber for small laboratory animal species being utilized in timed-dose studies. 6 references, 9 figures, 1 table.« less

Nitronic 40 was chosen for the construction of Pathfinder I, an R and D model for use in the National Transonic Facility, because of its good mechanical properties at cryogenic temperatures. Nitronic 40 contains delta ferrite and is in a sensitized condition. Heat treatments carried out to remove residual stresses also caused further sensitization. Experiments showed that heat treatment followed by cryoquenching removed the sensitization without creating residual stresses. Heat treatment at temperatures of 2200 F was used to remove the delta ferrite but with little success and at the cost of massive grain growth. The implications of using degradedmore » Nitronic 40 for cryogenic wind tunnel models are discussed, together with possible acceptance criteria.« less

Positron-emitting oxygen--15 with a half-life of 2.2 minutes has been prepared by bombarding air with deuterons at various energies between 8 and 14 Mev. The external beam from the cyclotron is used and the oxygen--15 formed by the (d,n) reaction on the nitrogen-14 is available with an activity of up to a curie per liter of air in an adjacent laboratory. Depending upon bombardment conditions, there is up to 5% contamination by carbon -- 11 (20 minute half-life) and its removal has been studied. The contamination by longer lived isotopes, in particular fluorine--18 (1.9 hours half-life), is very small. Theremore » is a slight contamination by ozone. In order to measure the distribution of gas and blood in different parts of the lung, the activated air is much diluted with inactive air, cleaned, monitored and passed into a spirometer from which a patient can take a single breath. The breath is held for a few seconds. The activity in different parts of the lungs is observed, by detecting the anihilation radiation using scintillation counters held external to the chest. The initial counting rate is a measure of the regional distribution of the active gas in specified parts of the lungs, and the fall in the counting rate over a few seconds is chiefly determined by the clearance of the active gas by the regional blood flow. The activity has been observed with a number of single scintillation counters, or with pairs of scintillation counters either in parallel or in coincidence, together with suitable recorders. The advantages and disadvantages of these three techniques for the localization of a small volume of non-functioning lung tissue have been studied. The absorbed dose both in the lungs and in the whole-- body has been calculated. Useful information can be obtained with activities small enough for normal subjects to take several breaths of gas without the absorbed dose approaching the maximum permissible level. (auth)« less