MTR STRUCTURE TEMPERATURES WITH 3 X 9 LATTICE--1953
The Materials Testing Reactor operated at 30 Mw, the design power level, throughout 1953. A 3 x 9 arrangement of the fuel assemblies was used until November 20 when a 5 x 6 lattice was introduced. No structure temperatures were observed which exceeded the maximum permissible levels for the various components of the reactor. The highest temperature observed in the graphite-ball zone was 175 deg F which is definitely below 300 deg F, the limiting operating temperature for a significant volume of graphite. The maximum variation of the observed thermal-shield temperatures was 18 deg F. The maximum design variation within a given section of the thermal shield was 33 deg F, and the resulting calculated thermal stresses were considered acceptable. The highest operating temperature in the concrete biological shield waa 99 deg F, which was less than 30 deg F above the temperature of the reactor room. From thermal-stress considerations the maximum acceptable temperature difference within a concrete structure is approximately 50 deg F. A master set of structure temperatures for 1953 is presented, and the temperature distributions withfn the various coinponents of the reactor are analyzed. The master sets of structure temperatures for 1952 and 1953 have been compared. Permanent facilities for measuring the emf's of the structure thermocouples were installed during the early summer. A double icejunction was provided for each thermocouple in order to eliminate thermocouple junctions at the selector switch and the potentiometer. With these facilities the agreement between duplicate measurements, with a time interval of one hour or greater, for most locations was within 0.5 deg F, and for many temperature points the variation was less than 0.2 deg F. (auth) 2O76 High activiiy levels have developed in the process water system of the MTR, indicating fission breaks in the fuel assemblies. Examination of fuel assemblies after use shows blemishes on the outer surface of the outer fuel plates. Not all elements have blemishes nor are there any apparent statistics favoring one position in the reactor. The theory is that high temperature corrosion due to low water flow on the outside of fuel assemblies is the cause. The top and bottom end boxes of several elements were punctured with holes to encourage higher outside flows. This seems to alleviate, but not eliminate, the cause. Work on this is continuing as rapidly as possible. A more sensitive method for monitoring the process water for fission products has been developed. A side stream of water is passed through cation and anion beds. A gamma ray scintillation counter views the anion bed. By biasing out all activities below 1 Mev, only the short-lived iodine activities are measured (mainly 6.7-hour I/sup 135/). This technique cuts out the high background normally induced in the water and thus gives higher sensitivity. In addition, since it measures only short-lived activities, it records the average rate of production of fission products in the system. The cross section work during this period has been aimed at developing techniques for measuring fission cross sections and eta values on the crystal and time-of-flight spectrometers. Preliminary values of the ratio of sigma f/sub 238// sigma f/sub 235/ from 0.035 ev to 0.3 ev have been obtained. In the total cross section field, preliminary values for Np/sup 237/ were determined. The activation cross sections of Pa/sup 253/ have been inveatigated by radiochemical techniques. Large resonance activation integrals have been discovered which greatly affect the value of the cross section. The studies on graphite damage ae a possible fast flux monitor have been terminated. The measurement of Co spacing changes seems to be in the range most useful in MTR exposures. (auth)
- Research Organization:
- Phillips Petroleum Co. Atomic Energy Div., Idaho Falls, Idaho
- DOE Contract Number:
- AT(10-1)-205
- NSA Number:
- NSA-12-002075
- OSTI ID:
- 4328163
- Report Number(s):
- IDO-16146
- Resource Relation:
- Other Information: Decl. Mar. 27, 1957. Orig. Receipt Date: 31-DEC-58
- Country of Publication:
- United States
- Language:
- English
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