ML20207N791

Safety Evaluation Re Fast Neutron Fluence for Fracture Toughness Requirements for Protection Against PTS (10CFR50.61).Util Actions Acceptable

ML20207N791
Person / Time
Site:	Millstone
Issue date:	10/13/1988
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20207N786	List: ML20207N785 ML20207N791
References
NUDOCS 8810190360
Download: ML20207N791 (3)

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SAFETY EVALUATION _BJ THE_0FFICE OF NUCLEA_R_ REACTOR R,EGULA,T_ ION _

RELATING TO FAST NEUTRON FLUENCE FOR FRACTURE TOUGHNESS _ REQUIREMENTS FOR PROT _iCTION AGAINST PRESSURIZE _D THE_RMAL SHOCK EVENTS, 10 CFR 50.61 NORTHEAST NUCLEAR ENERGY COMPANY

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MILLSTONE UNIT 3 E9.C,K_E,T,NO 3 5p ,423 1.0 I,N,TRODUCTION By letter dated January 23, 1986, and the October 1987 revis H Section 5.3 of the FSAR, Northeast Utilities Company, licensee for the Mill one 3 plant, submitted information on the material properties and the fast reutron fluence -

(E)1.0 MeV) of the reactor pressure vessel in compliance with the -

requirements of 10 CFR 50.61 (Refs. I and 2). The following evaluation concerns ,

{ the estimation of the fluence to the pressure vessel for 32 effective full power year 1 of operation and the corresponding value of the RT and also the pressure vessel material and chemical composition.' Pts The Millstone Unit 3 analysis of the fast neutron flux at the inside diameter of i

. the pre Jre vessel was perforned using the DOT code with P g

.' approx .:ations and an ENDF/B based cross section set (Ref 3).S The estimate of the neutron source was also perfonned with two dimensional DOT calculations '

in the (R,z) and (R,6) geometries. Included in this estimate is the out-in fuel management strategy. Given that low neutron leakage loadings are used, these  ;

estimates are conservative. We find the methodology and the calculations of the fast neutron fluence to the pressure vessel conservative and acceptable.

) 2.0 E_V,ALUATION i

The controlling beltline material was identified to be the intermediate shell plate R9805-1 (Ref. 3). The equation specified in 10 CFR 50.61 as applicable for the Millstone 3 plant is:

M h RTpts = I + M + (-10 + 470 x uC + 350 x uC x N, ) f

$[

gn 0 where:

I = Initial RT NDT = 60'F h

M C

=

a uncertainty margin

'v/o Copper in shell plate B9805-1

= 48*F

= .05 u

{ N 9

= w/o Nickel in shell plate B9805-1 = .61

$h f = Peak fluence on shell plate B9805-1 for 32 effective full power years in units = 2.3 of 1019n/cm 2 ,

l Therefore:

=

RT pts 60 + 48 + (-10 + 470 x 0.05 + 350 x 0.05 x 0.61) x 2.3 0.27 e 108 + 24.2x1.25 = 138.3 *F The temperature value of 138.3* F is much lower than the applicable criterion of 270' F; therefore, it is acceptable for 32 effective full power years of operation. .

l The above evaluation is based on the currently in effect version c,f 10 CFR 50.61 which is in agreement with RG-1,99 Rev.1. However, RG-1.99 Rev. 2 has been published in May 1988, and the corresponding modifications of 10 CFR '

50.61 will be effected in the near future. The following estimate is based on the anticipated revision of 10 CFR 50.61.  :

I l RT = 108 + 31 (0.28-0.1010g f) = 108 + 31 0.244 = 108 + 2.3 = 110.3' F pts

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A temperature value of 110.3* F is more favorable than the previous estimate and

presents a larger margin to the applicable criterion of 270' F.

i In view of: -

(a) the Pressue-Temperature updating requirenents for the fracture toughness l 4

of the beltline material in 10 CFR 50, Appendix G, and [

(b) the fact that the RT value is readily available from the calculation ofthePressureTempINturelimits,and

' (c) the staff desire to be inforr'ed en the current value of the RTpts for all pWRs, we request that the licensee submit a reevaluation of the RT and a comparisontothepredictionofReference2alongwiththef80re  :

Fressure-Temperature operating limits which are required by 10 CFR 50, i Apperdix G. It should be noted that this reevaluation is a requirement of 10 '

CFR 50.61, whenever core loadings, surveillance treasurements, or other  !

J information indicate a significant change in projected values.  !

l With regard to chemical composition and properties, the controlling beltline l

material from the standpoint of PTS susceptibility was identified to be the  !

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interr'ediate shell course plate No. B9805-1. l i

The rinertal properties of the controlling material and the associated margin l j and chemistry factor were reported to be. l I l i

i  !

I

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Utility Submittal Staff Evaluation Cu (copper content, %) = 0.05 0.05 Ni (nickel content, %) = 0.01 0.61 I (Initial RTNDT, F) = +60 +60 M (Margin, OF ) = 48 48 CF (Chemistry Factor, UF)= ---

24.2 We concur with the selection of the controlling materials, the justification of copper and nickel content, and the initial RT NDT* -

3.0 SUWARY AND CONCLUSIONS We have reviewed the information submitted by the Northeast Nuclear Energy i Company, the licensee for the Millstone 3 plant, in accordance with the

, requirements of 10 CFR 50.61. We find the estimcted value of the fast neutron fluence to the pressure vessel to have conservative margins and thus is acceptable. The value of the RT based on this fluence estir.te is less thanthe10CFR50.61screeningENterionandisacceptable. We further find that the controlling material has been properly icientified. The justifications given for the copper and nickel contents and the initial RT are acceptable. ThemarginhasbeenderivedfromconsiderationofthebasNT for these values, following the PTS Rule, Section 50.61 of 10 CFR Part 50.

The staff concludes, based on the considerations discussed above, that the Fi'.1 stone Unit 3 plant satisfies the fracture toughness requirements for protection against pressurized thennal shock, tt.erefore: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) s':ch activities will i

be conducted in conpliance with the Conrission's regulations, and will not be inimical to the cornon defense and security or to the health and safety of the public.

4.0 REFERENCES

1. Letter from J. F. Opeka, Northeast Utilities, to C. L. Grimes, NRC, dated January ?3, 1986.

j 2. Millstone Nuclear Power Station Unit 3 FSAR Section 5.3, Revised October 1987.

Principal Contributor: L. Lois

! Dated:

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