ML20235K543

Forwards Addl Info Re 881216 Incident.Caused by Designers of Triga Mark I.Licensee Intends to Add Cleaning & Lubricating Rod Actuating Linkage & Cleaning of Housing Above Electrical Portion of Rod Actuating Switch to Annual Maint Schedule

ML20235K543
Person / Time
Site:	Aerotest
Issue date:	01/10/1989
From:	Ruby L REED COLLEGE, PORTLAND, OR
To:	Scarano R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
NUDOCS 8902270156
Download: ML20235K543 (2)

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Q: R E E D- C O LL E G E' ' Portland,8Q 72o2

. REACTOR FACILITY .l

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10 January '1989 1 Ross A. Scarano, Director Division of Radiation Safety and Safeguards U. S. Nuclear Regulatory Commission 1450 Maria Lane, Suite 210

- Walnut Creek, California- 94596-5368 L ' Re: Docket 50-228, R-112 t

SUPPLEMENT TO REPORT OF 1/6/89 ON INCIDENT OF 12/16/88

Dear Mr. Scarano:

l Persuant to a request from your staff, I am writing to supply some additional information regarding the incident referenced above.

SAFETY IMPLICATIONS In the hypothetical event 'that the operator does not terminate the power rise when the Safety-Rod UP switch sti::ks at 150 W, the ramp reactivity insertion with a rate less than $0.16/s, would result, after 4.3 s, in a period scram at 288 W on the 300-W scale. We proved this experimentally, since the situation is difficult to analyse theoretically, i.e. the Point Kinetic Equations are non-linear.

It is a tribute to the designers of the TRIGA Mark I that in a worst-case situation analysis, where all of the permitted $3.00 of excess reactivity were to be inserted into the core, and all scrams were to fail, the reactor power would rise to a steady value, albeit above the licensed limit, but nevertheless at which fuel integrity would be maintained (see Reed Safety Analysis Report Fig. 7-1).

PREVENTATIVE MAINTENANCE ,

We intend to add the cleaning and lubrication of the rod-actuating linkage (see enclosed sketch), and the cleaning of its / L IS gg22;gge3;nggs

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housing above the electrical _ portion of the rod-actuating; switch, to our Annual Maintenance Schedule, which is performed in January of every. year.

NOTIFICATION OF OPERATORS -

At .a meeting of operators and prospective operatives on this-date, the details ~of the incident were reviewed. The necessity for scramming the reactor under all circumstances of aberrant rod behavior was stressed. All personnel will further be required to read and sign off on copies of the incident report and.of this letter.

Sincerely, Lawrence Ru Professor Reactor Director i

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Sketch of Control-Rod Actuating Mechanism Showing Detachable Button And Mechanical Linkage L-_-__---__-__________-