ML17037C223

Letter Requesting a Modification of Plugs in the Upper End of the Non-Instrumented Incore Housings

ML17037C223
Person / Time
Site:	Nine Mile Point
Issue date:	04/11/1974
From:	Bartlett J Niagara Mohawk Power Corp
To:	Skovholt D US Atomic Energy Commission (AEC)
References
Download: ML17037C223 (10)

Text

AEC D RIBUTION FOR PART 50 DOCKET M"'IAL 3370 (TEMPORARY FORM) CONTROL NO:

FILE PROM: DATE OF, DOC- .DATE REC'D LTR MMO RPT 'THER Niagara Mohawk Power Corporation Syracuse, N.Y. 13202 Mr. James Bartlett 4-11-74 4-17-74 TO: ORIG CC OTHER SENT AEC PDR SENT LOCAL PDR D.J,Skovholt 1 si ed CLASS UNCLASS PROP INFO- INPUT NO CSRE C'= DOCKET NO:

XXX XXX 40 50>>220 I

DESCRIPTXON: ENCLOSURES:

Ltr requesting a modification to their facility Figure 81 - Incore HSG Plug Layout.

described in th following enclosures...... t Figure fII2.

ACKNOWLEDGED (40 cys encl rec'd)

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MOHAWK ERIE BOUI.EVARD WEST SYRACUSE, N, Y. I3202 April 11, 1974 Mr. Donald J. Skovholt Assistant Director for Operating Reactors yO lp Directorate of Licensing United States Atomic Energy Commission /pe 4gg Washington, D. C. 20545 1g Mr. Skovholt:

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Re: Nine Mile Point Unit 1 Docket No. 50-220 Pursuant to Section 50.59 of the Commission's Regulations, Niagara Mohawk plans to make a change in its facility under. Provisional Operating License No. DPR-17. Briefly, this change consists of installation of plugs in the upper end of. the non-instrumented incore housings.

The modification is designed to prevent the accumulation of radio-active scale in the non-instrumented incore housing flanges under the reactor vessel. The scale accumulation in these housings produces high radiation levels under the vessel and interferes with control rod drive maintenance operations.

The proposed facility modification provides for installation of plugs in the upper end of the non-instrumented incore housing as shown in Figure 1 attached. This will prevent the accumulation of radioactive scale in these incore housings. The four fuel assemblies surrounding the incore housing would be removed and the plug inserted. As can be noted from the attached figure, a fluid path is provided through a screen into the core housing from the area between the upper and lower core support plates. This will prevent any pressurization force buildup within the incore housing by providing equalized pressures in and out of the tube. The plug assembly cannot be forced completely out of the incore housing due to the normal positioning of the fuel assemblies and the length of the plug assemblies.

The twenty-two spare incore housing locations are shown on Figure 2.

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Mr. D. J. Skovholt April 11, 1974 U. S. Atomic Energy Commission The facility modification has been reviewed by on-site and off-site safety review committees who concur that the modification is in the best interest of maintaining a high degree of safety and reduction in personnel exposure.

Very truly yours, James Bartlett Executive Vice President

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