ML19261C220
| ML19261C220 | |
| Person / Time | |
|---|---|
| Site: | Indian Point  |
| Issue date: | 02/23/1979 |
| From: | Carew J BROOKHAVEN NATIONAL LABORATORY |
| To: | Morris W Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19261C221 | List: |
| References | |
| NUDOCS 7903200204 | |
| Download: ML19261C220 (3) | |
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February 23, 1979 Mr. Bill Morris Phillips Bidg.
Rn. 521 Reactor Safety Branch Df vision of Operating Reactors U.S. Nuclear Reguiatory Cormrission
'4ashington. 0.C.
20555
Subject:
Review of SwRI Pressure Vessel Fluence Calculation. for Indfan Point-2
Dear 8111:
The revfew of the subject calculations requested in your IctterI of Janu-ary 29 and described in the SwRI Report 2 has been completed.
As ind i c.1 ta<f in your letter, this review was confined to the determination of tha pressure ves-sel neutron fluences and does not address the specimen material test evalua-tfans or the construction of the heatup or cooldown curves.
The following is the result of our review and discussions heTd with con Edison and Westinghouse.
The SwRI evaluation of the neutron fluence at the 1/4 T and 3/4 T pressure vessel locations con sts of the following three calculations:
(1) using the measured 5'Fe (n,p) dostmeter activities the fluence acctruiated at the capsule is detemined (2) the factor by which the capsule fluence leads the maximum pmssure vesse,i fnner wall fluence, the capsule lead factor, is calcu-lated and (3) the fluence attenuation from the inner wall to the 1/4 T and 3/4 T thickness locations is detemined.
The following fs a befer discussion of these steps including questions of significant concern where approprf ate.
1.
Capsule Fluence Deteminatfon.
The average flux density (fluence per unf t tiow) at the capsule, +, is de-temfned front the relation, sat N, d where k t is the infinitely dilute saturated activf ty per unf t mss N
is t or target atoms per tmit mass and 6 is the spectrun averaged bF8(n.p)he cross section.
Using the average of five measured 5% (312.5 d hal f life) 7903200Ao/
Page 2 of 3 N. 8111 Morris rebruary 23, 1919 bstmeter activities and the power history over the past s 3 years S RI has de-w tarwirr d Asat.
The cross section, 6, was determined from the ENDF/B-IY dosi-
.aetry file and a spectrum determined from a 22 group, 58, P; Dot 3.5 calcula-tion of the capsule.
cn moo rran s_co na ce ene s s,n r m so mea s u rec tne a c t r v i t i e s ro r - tu (n.a) o, g(n.p)2Co and 59Co(n,y)60Co dosfrneters.
The capsuie-T flux den-sity for these dosfmeters is as follows:
2 Dosimeter 9 (n/cm -sec) x 10-10 b(n.p)b 4.51 3 [
M j
53Cu(n m)Co 4.6 /v o
58Mg(n.pfCo 5.17 The discrepancy in these values is consistent with the s 15% uncertainty (15%
cross section and 31 activation) claftned by con Edison; however, the Icas t con-servative measurement was selected.
Question 1.
How was the fluence perturbation introduced by the survell-lance capsule taken into account in determining A i
sat Question 2.
What is the effect on & of using a Py rather than a P3 scat-tering expansion in determining the spectrum?
2.
Survef11ance Capsule / Maximum Pressure Yessel Fluence Lead Factor.
The original Westinghouse Indian Point-2 F5AR Tead factor ms 2.6.
In a letter frae Westinghouse to Con Edtson (Ref.15 in the SwRI Report) this vaTue was updated to 2.9 in 1975.
S (DLC-37) CASK Library and an (wRI recalculated the lead factor using the RSIC r.e) Dot 3.5 model in the 58, Pj approximatfon, and obtained a value of 2.6.
These df screpancfes are consistent wIth tbe 15%
uncertainty in lead factor claimed by Con Edf son; however, the least conserva-tive value of lead factor was used in the analysts.
3.
Pressure Yessel Attenuation Factors.
The S/I Dot 3.5 analysis predicts an attenuation or 50. and 8.5 percent at the 1/4 T and 3/4 T locations.
These results are in agemt with previ-ous calculations performed by the Naval Research Laboratory of 46 and 10 per-cent at the 1/4 T and 3/4 T Iocations, respectively.
However, a t the req'sest of the MIC staff values of 60 and 15 percent have been employed f a the SwRI analysfs.
This conservatism is intended to account for uncertainties in tha fluence deturwination as well as the effect of lower energy (.1 < E < 1 MeV) neutrons.
~
V890 3 or 3 Mr. Bill Morris February 23, 1979 When the results of steps (1) and (2) are com6ined, a ruxfmur, pressure vessel inner wall fluence of 2.5 x 1018 n/cm2 and 1.6 x 1019 n/cm2 (E > I MeV) at 5 and 32 effective full power years (EFPY) of operation, respec., resul t.
The original Westinghouse Indfan Point-2 % n/cm2 (E > 1 MeV) prediction of EUL (32 EFPY) pres-sure vesseT fnner wall fluer:ce was 2.4 x 10 However, in view of the changes in the Westinghouse methods,* f t is believed the rnost ac-curate method of inferring the Indian Point-2 EOL flueng is tg) reduce the most recent Indf an Point-3 Westinghouse prediction (1.8 x 10 n/cmd by the ra tio of pn/cm2 which is in good agreement with the SwRI prediction of 1.6 x 10 9 unf t-2/unf t-3 power ratings.
This results in an EOL fluence of 1.64 x 101 3
n/cm2, It is expected that the ongoing 8ML analysis of the pressure vessel do-simetry benchmark experiment (DOR program for calculation or radiation enbrittie-nent of power reactors) will provide certainties involved in steps (1) - (quantitative estisiates of many of the un-3).
References 1.
- 5. MurrfI to D. J. Utamond Tetter, January 29, 1979.
2.
E. 5. Morris, " Reactor Vessei Material Surve111ance Program for Indian Point Unit No. 2 Analysis of Capsale T*, Southwest Research Institute, June (1977).
Sincerely yours,
<~- f )
w
- John F. Carew Reactor Core Safety Analysts Group JFC:emur cc:
D. J. Ofamond W. Y. Kato S. Weiss P. Check The Westinghouse predictions of EE. fluence have decreased by s 30% due to a conversfon from the PING / SPIC-1 to Dot 3.5 nethods.