ML19210A570
| ML19210A570 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 02/21/1978 |
| From: | Herbein J METROPOLITAN EDISON CO. |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| GQL-0282, GQL-282, NUDOCS 7910300608 | |
| Download: ML19210A570 (3) | |
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READING, PENNSYLVANI A 19603 TELEPHONE 215 - 929-3601 Feb-uary 21, 1978 GQL 0282 Office of Nuclear Reactor Regulation U. S. Nuclear Reguatcry Conmission Washington, D. C.
10555 8('e,
Dear Sir:
$',. * 'S,' :.
%,, 's.
m.
- 4 e 'M
,y Three Mile Island Nuclear St atien Unit 1 (O!I-1)
- a ff '
Operating Licence No. DPR-50 Dceket No. 50-289 Your letter of February c, w ro, rescrted information regarding the reactor cavity annulus seal ring and associated biological shielding over the reactor vessel cavity. The following is hereby submitted:
(a) During normal operation of IMI-1, the reactor cavity annulus seal ring is not left in place; it is supported approximately 5" above the cavity annulus. However, during nor=al operation, biological shielding in the form of sand-filled shield plugs is installed in the cavity annulus.
(b) During the licensing stages of TMI-1, discussiens were held with the NRC (then AEC) concerning the design of the sand-filled shield plugs.
Calculations were perfomed to verify that the sand-filled shield plugs would rupture as a result of a pipe break inside of the reactor cavity annulus. O!I-1 was subsequently licensed to operate with the sand-filled shield plugs. Ecvevee, in an attempt to fully address your letter of February 2, 1978, Metropolitan Fd-isen Company has made the conservative ass';mption that the shield plugs vould eject intact 2nd uni =peded and si..-ike the annulus seal ring (at which time the shield plugs would rupture).
'"he seal ring could then potentially beccme a missile.
(c) Because of the potential that the seal ring could becere a missile, Met-Ed is considering removal and/cr relocaticn of the; cavity ann tlus seal ring during normal operaticns. Met-Ed intends to evaluate the impact of the above acticn and resolve the issue prio-to the Cycle h startup.
(d) The-probability of the previcusly analyzed pipe break cecurring inside of the reactor cavity annulus is censidered to be extremely remote.
The prcbability of this accident occurring before the end of Cycle 3 is even more remote. Combined with the censervatisms assumed for the seal plate to become a pctentially damaging missile, the possibility pO k 1491 306 N
I
s Off,4 ce cf !iuclear Reactor Regulation heornary 21,1978 GQL 0232 of an accident of this type is considered incredible. "herefore, continued operation does not create undue risk to the health and safety of the public.
Sincerely,
/
J. G. Herbein Vice President-Generation JGH:PJS:cjg 1491 307