NRC Generic Letter 78-03, Request For Information On Cavity Annulus Seal Ring

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GL78003

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555

FEBRUARY 2 1978

All PWR Licensees (except for Trojan)

Gentlemen:

During the course of responding to the staff's review of an application for license amendment on the Trojan Nuclear Plant, the licensee informed the NRC that the reactor cavity annulus seal ring (used as a water seal during refueling operations, and not removed during normal operations) and associated biological shielding over the reactor vessel cavity could become missiles in the event of a loss of coolant accident (LOCA) pipe break inside the reactor vessel cavity. At the Trojan Nuclear Plant, these missiles could affect the ability of the control rods to shut down the reactor. From our preliminary evaluation of the information provided to the NRC staff by the licensee, the Portland General Electric Company and by Westinghouse, Combustion Engineering, Babcock & Wilcox and Bechtel in telephone discussions on January 25 and 26, 1978, it appears that this problem could occur in other PWR facilities such as yours and could potentially pose a threat to the health and safety of the public in the event of a LOCA.

Therefore, pursuant to 10 CFR 50.54(f) of the Commission's regulations, you are hereby requested to deliver to the Office of Nuclear Reactor Regulation, Nuclear Regulatory Commission, Washington, DC 20555, within 20 days of the date of this letter, i.e., February 22, 1978, the following information:

(a) a statement as to whether the cavity annulus seal ring in your facility is left in place during normal operation or if biological shielding is installed in the reactor cavity annulus and, if the answer to

(a) is yes;

(b) when you will determine whether the cavity annulus seal ring or biological shielding could become a missile in your facility, and

(c) a description of what you plan to do, and when, if the problem is found at your facility and

(d) justification for continued operations until the problem has been resolved, such justification to support why continued operation will not create undue risk to the health and safety of the public.

A copy of this letter is being provided to each licensee's current service list.

Sincerely,

Victor Stello, Jr., Director Division of Operating Reactors Office of Nuclear Reactor Regulation