ML20024G857

Forwards Suppl to Change Request 2 to License DPR-22,per 711027-28 Safety Audit Committee Meeting Re off-gas Sys Mods

ML20024G857
Person / Time
Site:	Monticello
Issue date:	12/10/1971
From:	Ward E NORTHERN STATES POWER CO.
To:	Morris P US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20024G858	List: ML20024G857 ML20024G859
References
NUDOCS 9105010218
Download: ML20024G857 (3)

Text

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NORTHERN STATES POWER COMPANY ,,,

m ~ ~ e . o u . . m ~ ~ . . o r. o . . 50-263 December 10, 1971 P o i S  %

Dr Peter A Morris, Director p Division of Reactor Licensing -

U S Atomic Energy Commiesion C OE02 k'ashington, DC 20545 t'

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Dear Dr Morris:

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MONTICELLO WCLEAR GENERATING PLANT E-5979 "'L0 Supplemental Information - Change Request No. 2 Attached are three signed originals and nineteen conformed copies of Supplemental Information for Change Request No. 2, to operating License No. DPR-22. ,

Under separate cover, we are eending you 40 copies of the supplementing technical information on the following items:

(1) Design basis for the filter and computation of anock wave attenuation in the recombiner system. i (2) Verification that the dilution flow to t:

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vill be maintained constant. -

At its October 27-28 meeting the Safety Audit Committee further reviewed the safety considerations related to the off-gas system modifications and concurred with the favorable recommendation of the plant Operations Cor:mittee.

In reply to your inquiry, the proposed modifications do not present significant l hazards considerations, as defined in Section 50.59 (e), for the following reasons:

(1) The vorst case accident dose at the nearest boundary of the exclusion area is calculated to be 1.ess than 10 cer cert of the 25 rem whole body dose set forth as a guide in 10 CFR 100.

(2) The accident dose referred to above has been calculated based on the instantaneous release of all of the radioactive gases and particulates contained in the storage system together with inversion type meteorology.

No clean-up systems or physical phenomenon such as radioisotope plate-out have been assumed to mitigate tho effect of the accidental release.

(3) Lethal and highly combustible gases are routinely stored at elevated '

pressures in a large number of industrial applications, and catastrophic 3

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failure of such storage systems is very rare. Based on this long-term

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(1) Supplemental Information to Change ,ABC PDE Rey est No. 2 motarised 12-10a71. c m itance w (3 Oris & 19 conf'd cys rec'd) 00C. he P 506A (t) Supplemental Answers to DRI. Muntzing ei statt Questions.(40 cys ree'd) Skovhole E. M e ma Thompson

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p l.5 industrial experience, the prcbability of a storage tank failing in p such a way as to cause an instantsneously release is exceedingly small.

f, However, to further reduce this failure probability, the high pressure P' storage system is designed, fabricated, and constructed to meet the stringent nuclear code; ASME Section III Class C (1968) for the tanks L

"" and Class 2 (1971) for the piping system. In addition, the gas storage building and supporting structures are designed to withstand the design

, basis earthquake (seismic Class I), the probablo raximum flood, and the

, , . design bssis tornado.

p ., (4) The storage of radioactive gas at elevated pressures has been pre-i viously reviewed by the Comission and judged uo be acceptable for

p. , numerous pressurized water reactor system applications.

x v , As wo earlier informed members of your staff, wo have begun site preparation work C for this installation so that the benefits of the system can be available at an P czrly date. Excavation work is now underway and construction of the required l, buildings vill follow. We have made commitments for certain major pieces of

.r '. cquipment and are in the process of procuring other required material and equip-ment. Following your approval of the installation, certain equipment details vill y be finalized and installation of equipment vill proceed.

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