ML19259C183

Supplements Response to IE Bulletin 79-07.Assessment Revealed Nitrogen Addition Sys & Charging Sys Are in Conformance W/High Energy Pipe Break Criteria Specified in FSAR

ML19259C183
Person / Time
Site:	Millstone
Issue date:	06/08/1979
From:	Counsil W NORTHEAST NUCLEAR ENERGY CO.
To:	Reid R Office of Nuclear Reactor Regulation
References
NUDOCS 7906140277
Download: ML19259C183 (2)

Text

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g June 8, 1979 Docket No. 50-336 Director of Nuclear Reactor Regulation Attn: Mr. R. Reid, Chief Operating Reactors Branch #4 U. S. Nuclear Regulatory Commission Washington, D. C. 20555

Reference:

(1) W. G. Counsil letter to R. Reid dated May 23, 1979.

Gentlemen:

Millstone Nuclear Power Station, Unit No. 2 I6E Bulletin 79-07 In Reference (1), Northeast Nuclear Energy Company (NNECO) responded to a verbal Staff request to address the impact of piping modifications previously described on the High Energy Pipe Break (HEPB) studies documented in the Millstone Unit No. 2 FSAR. Within that submittal, NNECO reported that four of the six piping systems previously identified were not originally subjected to detailed HEPB review, hence, the HEPB study previously docketed remains unaffected by the modifications to those systems. NNECO also reported that an evaluation of the remaining two piping systems, the Nitrogen Addition System and Charging System, was underway, with results to be reported on or about June 8,1979, h3ECO has completed this evaluation and has determined that these two systems remain in conformance with HEPB criteria specified in the Millstone Unit No. 2 FSAR.

The basis for this conclusion is described below.

Nitrogen Addition System (Steam Generator Blowdown Lines)

Subsequent to the NRC Staff request for an assessment of the effects of modifica-tions made to the subject system on the HEPB evaluation previously docketed, NNECO had contacted the architect engineer, Bechtel Power Corporation, and requested that an assessment be conducted. Bechtel has completed their evaluation and concluded that the minor changes made do not affect the existing physical separa-tions and break / blowdown characteristics of the steam generator blowdown lines.

Hence, the impact upon the HEPB evaluation previously performed is insignificant and the conclusions remain valid.

2278 335 7906140777

Reactor Coolant Charging System The initial liigh Energy Pipe Break (llEPB) evaluation of the reactor coolant charging system is reported in Section 5.9 (Amendment 34) of the Mill. stone Unit No. 2 FSAR. NNECO Ins investigated the ef fects of modifications made to the system with regard to effects on the HEPB cvaluation reported therein.

As reported in Section 5.9.3, the only piping or equipment required for safe shutdown, which is addressed with regard to potential pipe breaks in the charging system piping, is a portion of the high pressure safety injection pump discharge piping (2"-DCB-1) and conduit and cable trays located in the west piping penetration room.

As previously reported, only minor geometry changes were made to the original charging pump discharge piping. The modification to the system involved only a discrete portion of the discharge piping bounded by terminal points. Stress levels and postulated break locations luve only been impacted within this discrete section of the piping system. An investigation of the geometry of the charging system discharge piping has shown that the critical portion of the system with regard to HEPB protection is the section from break location RC9 shown on Figure 5.17 of the FSAR to the containment penetration (RCl, Figure 5.16). As reported in Section 5.9.5 of the FSAR, four whip restraints were provided on the charging system discharge piping, in the vicinity of the two-inch high pressure safety injection line. All four whip restraints are on this portion of the charging line. This portion of the line was not modified, reanalyzed, or af fected by the modifications to the system. The remainder of the charging system discharge piping is sufficiently distant from the two-inch safety injection piping, such that for any postulated charging line rupture, damage to that piping due to pipe whip is not credible.

The conclusions made regarding compartmental pressurization and environmental ef fects in Section 5.9.5 and 5.9.7 of the FSAR are not dependent upon break location; therefore, they have not been hnpacted by this modification.

Jet impingement is of concern only with respect to effects on cable trays, cables, and conduit located within the west piping penetration room. As previously discussed, this portion of the charging system piping has not been af fected by modifications to the charging system. The conclusions made regarding jet impingement effects due to a charging line break therefore remain unaffected by the subject modification.

We trust you find the above information responsive to your verbal request.

Very truly yours, NORTHEAST NUCLEAR ENERGY MPANY

// f WZ W.' G. Coun'sil '

Vice President 2278 ;36