(a) "The meteorological study on the stack gases, particularly under adverse conditions in the immediate vicinity of the stack, should be continued". Studies are now in progress on the relationship of exhaust air trajectories as a function of meteorological conditions and the possibility of hazard from any radioactive effluent that might be released. These studies will follow two lines: (1) visual observation of smoke paths from the top of the stack under various weather condi- tions, (2) area monitoring by radiation instruments when low levels of radioactivity are present in the effluent.

The results of these studies will be used as a guide to the safe operation of the reactor at successively higher levels. Any significant conclusions drawn from these studies will be reported at appropriate intevals.

(b) "The open water reservoir of the Raleigh system should be periodically monitored". The scheduled duties of the Radiological Safety Officer include periodic monitoring of water samples from the Raleigh watershed and reservoir, after routine reactor operation is established. An interval of 3 or 4 months between sampling periods is anticipated.

(c) "A direct connection of the tap water to the potentially contaminated line leading to the coils within the reactor is undesirable. Other possible cross- connections via the water system should be detected and eliminated." A complete break in this line has been provided, as agreed. No other connections offering possibilities of contamination are known to exist.

(d) "It was noted that a procedure for evacuation of the area in event of a major disaster will be formulated". For initial operation of the reactor, up to a power level of one Kilowatt, a building evacuation plan already worked out, will be followed. Upon appropriate alarm signal, all personnel in the building will move by the nearest door or window exit from the building to the street bounded edge of the area (about 100 feet from the reactor). Designated persons will immediately begin a monitoring survey to determine whether any unsafe conditions exist.

2. Suggestions of the visiting committee:

(a) As finally installed, the instrumentation system of the reactor (9 indepen- dent channels during start up and low level operation, 6 during subsequent operation at high power) differs somewhat from the plan described in report NCSC-46.These changes developed through efforts of the reactor staff to develop a more dependable, safe system of instrumentation. The general plan and philosophy of safety have been in no way changed. A brief review of the pertinent changes in instrumentation was given to the visiting group. One change involved the installation of a relatively slow operating trip of about 2 seconds on the period measuring channel. (This was offset by addition of fast trips on other channels...to a total of 5 channels). It was suggested, however, that this period measuring circuit be revised to include a 0.2 second trip mechanism for reactor operation at lower levels. This change has been made. It was further suggested that added speed of response "to the smallest delay practicable" on the trip mechanism be provided for operation at high power level. This will be done.

(b) A description was requested of the special precautions which will be taken to prevent a person from being inadvertently exposed to the radiation beam from an open beam port. In most cases, the reactor will not be in operation when a beam port is open. After any adjustment of the shielding plugs in the beam ports, a check of the radiation issuing therefrom will be made immediately after the reactor is placed in operation again, and before persons are permitted to circulate in the area. In special cases where a beam port is to remain unplugged during reactor operation, two general precautions will be taken to prevent exposure: (1) access to an appropriate area near the beam will be prevented by rope or chain barriers on which warning signs are hung, and (2) appropriate shielding along the beam path to prevent hazard from scattered radiation will be provided. The details and extensive- ness of those two precautions will depend on the circumstances in each particular case. If a very small beam emerges, e.g. into a small crystal spectrometer adjacent to the reactor shield, only little shielding will be needed. If a large beam emerges and crosses the room to the permanent trap in the wall, a tunnel of concrete blocks along the entire path will be required.

(c) The landscaping plans for the area adjacent to the reactor building require the removal of considerable quantities of earth, before grass and shrub planting can be started. After this grading has been completed a thorn hedge will be planted around the perimeter of the area. Until the hedge is planted, and until it becomes sufficiently large to present a serious obstacle to access, the perimeter of the building itself will constitute the physical boundary of the exclusion area. The building walls are about 55 feet from the center of the reactor.

(d) The half curie radium-beryllium source obtained for use as the neutron source in the reactor was found to be too large to fit inside the re-entrant tube in which it was to have been located. In the alternate plan devised, the source is inbedded in paraffin in the hollow end of an otherwise solid wooden rod, 3 inches in diameter and 8 1/2 feet long. This rod fits snuggly in the beam port which