ML20125A429

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Provides Suppl Rept to ACRS Re Facility SE on 691124, Discussing Matters Including Site Flooding,Inservice Insp, Seismic Design Adequacy,Instrumentation & Control Items & Turbine Bldg Secondary Closed Cooling Water Sys
ML20125A429
Person / Time
Site: Millstone Dominion icon.png
Issue date: 12/24/1969
From:
US ATOMIC ENERGY COMMISSION (AEC)
To:
Shared Package
ML20125A422 List:
References
FOIA-92-198 NUDOCS 9212080342
Download: ML20125A429 (9)
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,OFFHCHAL USE ONLY Docket No. 50-245 December 24, 1969 Supplemental Report to ACRS MILLSTONE NUCLEAR POWER STATION UNIT 1 1

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1.0 INTRODUCTION

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SUMMARY

In our report to the ACRS, dated November 24, 1969, containing the results of our safety evaluation of the Millstone Unit 1 facility, we indicated that we would report orally on certain matters. These matters, referenced to the applicable section of our initial report, are as follows:

- Site flooding potential (Section 3.3)

- Inservice inspection program with regard to the recirculation nozzle welds and the vessel support skirt (Section 5.4)

- Adequacy of analytical methods used for the seismic design of the f acility including Class I piping (Section 6.1)

- Instrumentation and control items consisting of single failure protection for auto-relief interlock and containment spray system control; monitoring capability of Target Rock relief / safety valve bellows integrity; design apn11 cation of the single f ailure criterion; and indenendency provisions for the standby gas treatment system (Section 8.4)

- Turbine building secondary closed cooling water system (Cection 9.3)

These matters have been further discussed with the applicant, and addi-tional information was provided in Amendment Nos. 21 and 22, dated December 5 and December 19, 1969, respectively. This additional informa-tion has been reviewed and our evaluation is presented in this report.

Our review of the Millstone Unit 1 Technical Specifications is continuing and the draft proposed by the applicant (Amendment No. 20) has been CFFHCHAL USE ONLY ~

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. OFFHCHAL USE ONLY-provided to the Committee. Subject to development of final Technical l Specifications and satisfactory completion of construction and preopera-tional tests, we conclude that Unit 1 may be licensed for operation.

2.0 DISCUSSION 2.1 Site Flooding Potential As indicated in our initial report, the applicant has performed analysis of flooding at the site due to the probable maximum hurricane. The entire structural periphery of the Unit 1 facility is protected to an elevation ,

of +19 f eet MSL by reinforced concrete walls topped of f by 2-inch-angle iron. All external entrant.es are provided with rubber sealed flood gates to this elevation. Data provided by the applicant indicate that the probable maximum surge water level would not exceed +16 feet MSL; how-ever, our consultant on this matter, Coasts 1 Engineering Research Center (CERC) has estimated a maximum surge level of +18.2 feet MSL and wave runup of the order of 2.5 feet. This results in a maximum water elevation of +20.7 feet MSL according to the CERC model. The report from CERC has been provided to the Committee.

Although the applicant and its consultants consider the higher water i level event extremely unlikely, they have provided additional information on plant capability using the CERC model. The analysis predicts a maximum i

l- surge level below the level.to which the plant is protected but wave l

l l runup could possibly result in water seepage into portions of the facility .

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l structures other than\the reactor buil ing, whi, , flood protected to L OFFHCHAL USE ONLY ~

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3 elevations well above +25 feet MSL. The applicant's study also indientes that safe shutdown can be accommodated and maintained since critical equipnent for such ection is protected to at lesst

+?S feet MSh. The critical equipment associated with such action '

is the teolation condenser, veter makeup and diesel generator.

  • We conclude that the level of flood protection pr'ovided for Unit 1 is acceptable in view of the plant capability for safe shutdown, even in the event of the low probability flood levels predicted by the CERC model.

2.2 Inservice Inspection Program In our initial report, we indicated that the applicant proposed not to include nozzle-to-vessel velds in the inlet an'd outlet recireuta.

tion lines and the velds in the vessel support skirt in the inservice insrection program. Beesuse of the safety significance of breaks in the nozzle regions, and because the shield blocks and insulation are removable in the region of the nozzles, ve have concluded that the applicant should develop means to include'the nozzles in the inspection pro 6 ram. As in the Dresden 2 program, we vill include this inspection requirement in the Technteel Specifications.

Access to the support skirt velds is not presently available. The

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applicant, however, proposes to study meana_e.n4Jo develop techniques for. remote inspection of this , veld regisq.. This action is stated in the bases to Technical Specification h.6 and is acceptable to es.:

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23 Adequecy of Analytical Methods Used in Seismie Design Additional information hos been provided by the applicant in Amendments 17,18,19 and 21 on stress levels in critics'. piping systems and on the analytical methods employed for dynamic analysis. The information has been found acceptable by Dr. Newmark, as discussed in his report which has beten provided to the Committee. We consider this matter to be resolved. .

2.h Instrumentation and Control Items 2.4.1 Containment Spray Control System Because of the heat exchanger especity of the containment cooling system,it is necessary that reliance be placed on containment pressure to assure adequate NPSH for the ECCS pumps. The Technical Specificatione ,

1 impose restrictions on torus veter temperature and on the operability of I the containment cooling system. - These actions' assure that the cooling cepscity would not degrade to a point where excessive- temperatures occur and complete relisnee on containment pressure is required for adequate-NPSH.

To give complete NPSH protection, inadvertent actuation of containment-sprey is -prevented and similarly the spray action is terminated +

, automatically when the containment pressure decreasts below a preset value.

The applicant has improved the design of this containment spray interlock -

to provide single failure protection against inadvertent spray actuation, but has not provided the'same single failure protection for the automatic  !

termination of containment spray. However, manual termination of.sprey.

operation in possible and the manual control circuitry is designed to:

the single failure criterion. ,

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In Amendaent No.16 (Figure D-1.h), the applicant shows that with two containment cooling leops in operation, ECCS pump NPSH require-ments are satisfied whether or not the containment sprays are in operation. As indicated in our initial report, we vill require the two containment cooling loops to be operable as a limiting condition of operation _

We conclude that the containmaa+ epeey-control-eyete- i= acrttgage. _

2.h.2 ECCS Lov Pressure Auto Relief Interlock The interlock function is provided by an arrangement involving six

, pressure switches (one switch for each ECCS pump) monitoring pump discharge pressure. The interlock is a permissive - type which allows initiation of auto-relief when one of the six switches responds to either the pressure characteristics or to a circuit failure which produces the same signet to the auto-relief system as the pressure characteristic. Therefore, a single failure which produces a permissive condition vould defeat the parpose of the interlock in cases when non-permissive circuit orientation is required. We believe that eingle feiture immunity is required for this particular design aspect.

The applicent has not agreed to this requirement. We plan to require that the design be modified to provide protection against this mode of failure.

2.4.3 Monitoring Canability of the Integrity of Bellows on the Target Rock Relief /Sefety Valves Beesuse the integrity of the bellows is essential to the self-actuated operating mode of the Terget Rock relief / safety valves, we conclude that the testing circuits associnted with bellows integrity monitoring e OFFHCHAL USE ONLY -

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1 should be l'aproved to effect unemby;uput, t e a t t ar.. 'i he " onl i ce nt

/> 'N r st*ted such c"nb111ty would be provided in the Millstone design, and

[c, we conclude that this is t eeeptable. We shall review the specific design detnil.s trier to issuance of an operating License to ensure th+ t these recuirements are satisfied.

2.h.h SinM e Failure criterton The a nMicent hat, stnted in Amendment 21 that the renetor protection and cont"Inment isointion systems ere designed to meet the single feiture criterion per IEEE 279 The ECCS is designed with protection eguinst effects of sinBle failures negating effective core cooling.

We conclude that this design is adequate.

2. l+ 5 Standby Ces Treatment System (SBGTS) tr Amendmen. 2l, the applicant indicated that the SBGTS would be designed to meet the single.feiture criterion but did not agree to completely satisfy lEEE 279, which was the original canmitment. Although the system contains ndequate physical and electrical separation the control instrumentotion of one equipment chnin is dependent on another; i.e. , onerotion of n redundant equipment chain is dependent upon the fniture of ito redundant counterpart for initiation and operation.

We bmve concluded that provision; should be med? to provide for independence of redundant control nnd initiatien circuitry and plan to require such action.

25 Turbine Building Secondary Closed Cooling Water System (TBSCCW)

As noted in our report, the TBSCCW system provides cooling for the ECCS l

upper pumo. motor benrings. We indicated to the applicant and GE that

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a failure of the TBSCCW system apparently could lead to a loss of cooling of the bearing lubrication oil. Subsequent overheating of the bearings could possibly result in total failure of all ECCS pump.

motors. In response, the applicant has p./oposed plant design changes that voo i n'... ide en alternate coolf ag system to the various ECCS pumps. Such action was stated in Amendment No. 21, along with a dis-cussion of several possible methods. Subsequent discu'ssions with the applicant were held and Amendment 22 describes the method to be employed-which consists of providing coolant to the ECCS pumps from the torus -

veter. This method of cooling is the same as that employed in ths Dresden 2/3, Oyster Creek and Nine Mile Point facilities. We conclude-that this arrangement is acceptable.

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30 Conclusions We and the applicant do not agree on actions taken regarding certain review areas. These matters are listed below along with a summary of our positions for the C~nmittee's reference.

. Containment-Cooling System-(Section 7 5 of initial report)

Because of concern on NPSH and the small heat removal capacity,.

we consider that both containment cooling loops must be opgrable as a -limiting condition for continued planLoperation. -Minimum requirements for equipment operability (including plant emergency power systems) and. limitations on the time that equipment can:be out-of service for maintenance vill be included in the Technical Spe cifica tions.

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- 8-Inservice Inspection Program (Section 5 4 of initial report and 2.2 above)

We vill include the nozzle-to-vessel velds in the inlet and outlet recirculntion lines in the inservice inspection program.

- Auto Relief Interlock (Section 8.4.5 of initial report end 2.4.2 above)

We vill require that the interlock with regard to the pressure switches be made immune to the effects of single failures.

Standby Gas Treatment System (Section 8.4.8 of initial report end

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2.4.5 above)

We vill require that provisions be made for independence of i

redundent control and initiation circuitry.

- Containment Inerting (Section 6.4 of initist report)

We vill require that the containment be inerted following comple-tion of the plant start p and power ascension test progrem.

If the actions indicated above are token, we corelude that Millstone Unit t can be operated without endangering the health and safety of the public.

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