ML20215E327
| ML20215E327 | |
| Person / Time | |
|---|---|
| Site: | Berkeley Research Reactor |
| Issue date: | 09/27/1966 |
| From: | Mark H CALIFORNIA, UNIV. OF, BERKELEY, CA |
| To: | Doan R US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20215E220 | List:
|
| References | |
| FOIA-86-811 NUDOCS 8612220124 | |
| Download: ML20215E327 (2) | |
Text
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ti COLLECE OF ENGINEERINC l BERKELEY, CALIFORNIA 94720' DEPART &fENT OF NUCLkAR ENCINEERING
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Septo'mber 7,e1966 o
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.x Mr.,R. L. Doan~'
1" Division of Reactor Licensing 4
U. S. Atomic Energy Commission
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Washington, D. C. - 20545 y
Dear Mr. Donn:
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On the morning of September 10, 1966, during oporation of
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the TRIGA Mark III Reactor, there occurred an incident which under the stipulations of our license, required an~immediate t
report to the Division of Compliance.
This report was made by Lawrence Ruby, Roactor Supervisor, directly following the incident, by telephone to Mr. Walter Vetter of AEC/ SAN who responded by visiting the facility.
The incident occurred when, during.the routine course of period measurements, the safety rod was dropped and it stopped in a position about 150 units out of i
the core.
The malfunction was first evidenced,when it was noticed that the safety-rod drive, mechanism was driving itself up, without the controls being manually actuated.
This is characteristic of those TRIGA Reactors which require ther \\
falling rod.to trip a rod-down switch which, in turn, removes-an anti-slip voltage from the rod-drive motor, and impresses'a
-down voltage.
Had the rod dropped all the way, the bottoming switch would have been engaged and'the rod-drive mechanism would have returned to the down position along with the rod, l
TheproblemwasidentiflodalmostimNdiatelyasbeingdue t
- 4 to a clamp which had been installed on September 17, 10GG by tho General Atomic representativos on the safoty-rod guido tube.
Similar clamps were also installed at the sape time on the regulating'and shim-rod guido tubes.
Although installed lato, theso clamps woro, according~to,the G. A. representativos, part of the original rod design and are'shown on detail drawings in their possession.
The clamps woro installed for the purpose of closing two vont holos in the guide tubu, to componnato for the additional weight of fuel follower control rods.
These closed holes increase the damping' action provided by the bott.omfof tho guide tubo.
In ordor to make a good seal, a shoot-rubber spacer was placed between the clamp and the guide tube.
In the caso of the safety-rod guide tubo, the rubbor spacor had bulgod through a slot in the tubo, thoroby proventing the fall of the safety rod.
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=Ddekst No. 50-224 September 7,
1966 (page 2) 4 r, s i
s Although the bulge could easily be removed by merely loosening and re-tightening.the clamp, we decided that a much more_ satisfactory solution would be to remove the rubber spacers from each of the i
clamps, and to replace them with a sheet-aluminum spacer.
After this change was effected, Mr. Vetter authorized restarting of the reactor, and he subsequently made,an inspection of the operational system _with the modified clamps.
In accordance with CFR 60.59, l'
the Reactor IInzards Committee has also been asked to approve. the modification to the clamps.
1 Finally, to reduce the possibility of a recurrence of an incident of this type, we have cautioned G. A. to obtain prior approval from us for all future additions to the system,however
- trivial, y
's Sincerely, fpy f&, Q Ilans Mark Reactor Administrator s
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R. W.
Smith,AEC/ SAN A. P. Graffi G. A.
S. Davis L. Ilughes t
L. Stollar L.' Ruby
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P. Kraker t
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