ML20059L406

Comment on Draft Reg Guides DG-1023, Evaluation of Reactor Pressure Vessels W/Charpy Upper-Shelf Energy Less than 50 Ft-Lb, & DG-1025, Calculational & Dosimetry Methods for Determining Pressure .... Supports NUMARC Comments

ML20059L406
Person / Time
Site:	Calvert Cliffs
Issue date:	01/31/1994
From:	Denton R BALTIMORE GAS & ELECTRIC CO.
To:	NRC OFFICE OF ADMINISTRATION (ADM)
References
FRN-58FR51392, RTR-REGGD-1.161, RTR-REGGD-XX.XXX, TASK-DG-1023, TASK-DG-1025, TASK-RE 58FR51392-00005, 58FR51392-5, NUDOCS 9402070011
Download: ML20059L406 (3)

Text

-

E VIM BALTIMORE GAS AND - U3

),iRC

,' - '- OF9. :

ELECTRIC " Wen <

94 FEP -3 p 7 39 1650 CALVERT CLIFFS PARKWAY LUSBY, MARYLAND 20657-4702 ROBERT E DENTON VicE PRESCENT January 31,1994 NUCLEAR ENERGY ((

(4@) 250 d455 [

U. S. Nuclear Regulatory Commission Washington,DC 20555 f>)

3 A'ITENTION: Rules Review and Directives Branch Division of Freedom of Information and Publication Services ,

Office of Administration

SUBJECT:

Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2; Docket Nos. 50-317 & 50-318 Comments on Draft Regulatory Guides DG-1023, " Evaluation of Reactor Pressure Vessels with Charpy Upper-Shelf Energy Less than 50 Ft-Lb," and ,

DG-1025, " Calculational and Dosimetry Methods for Determining Pressure ,

Vessel Fluence"

REFERENCES:

(a) Federal Register, Volume 58, Number 189, Page 51392, October 1,1993 (b) Letter from Mr. W. H. Rasin (NUMARC) to NRC, dated ,

January 31,1994, Industry Comments on Draft Regulatory Guides -

DG-1023 and DG-1025 Baltimore Gas and Electric Company (BG&E) actively participated in the development of industry ,

comments on the subject draft regulatory guides (Reference a) by the Nuclear Management and - -

Resources Council (NUMARC). Baltimore Gas and Electric Company strongly endorses the entire content of NUMARC's comments, which are being transmitted to you by a letter dated 1 January 31,1994 (Reference b). Additionally, BG&E offers the following supplementary comments concerning Draft Regulatory Guide DG-1025 for your consideration.  ;

i As discussed in the NUMARC comments, the logic and application of the Draft Regulatory Guide i DG-1025 (DG) are not clear and need to be better defined. For example, it is not clear how the DG .

applies each time an existing dosimetry for a surveillance capsule is analyzed and how this compares to application for new dosimetry materials or configurations. He DG needs process flow charts that l clearly define: (1) what must be done in the analysis of each surveillance capsule; (2) what must be . s done to qualify / calibrate new dosimeters; and (3) what must be done to validate analytical models.

These should be separate flow charts with interfaces between them and with other related  ;

regulations and standards clearly defined. The DG text should be organized around these flow 'j charts.  ;

9402070011 940131 PDR RECGD j XX.XXX C PDR

, - . ~. . - -

Document Control Desk ,

January 31,1994 i j Page 2 l A central theme of the DG is that the " absolute" neutron flux and fluence must be determined for ,

surveillance capsules and predicted for the vessel. However, it is questionable whether the so called

" absolute" values are needed in the application of the surveillance capsule results. The primary ~ i i

application of dosimetry and fluence calculations is to predict the state of embrittlement of reactor vessel belt-line material based on the embrittlement measured by surveillance capsule coupons. The trend curves of 10 CFR 50.61 and Regulatory Guide 1.99, Revision 2 already provide conservative - ",

embrittlement predictions at near-end-of-life fluences for the embrittlement-sensitive beltline materials in nearly all Combustion Engineering fabricated vessels.  ;

l Another major item discussed in the DG is the adoption of ENDF/B-VI cross-sections. This is '

i intended to address experimental findings that suggest ENDF/B-VI results in less fast-neutron -

attenuation by iron than ENDF/B-IV. However, it is questionable that an immediate need exists to ,

switch to ENDF/B-VI for surveillance capsule and vessel fluence analyses. There is little iron between surveillance capsule coupons and the vessel wall; hence there should be little difference between embrittlement predictions made with ENDF/B-IV based fluences and trend curves, and those made with ENDF/B VI based fluences and trend curves. Therefore, ENDF/B-VI should be gradually phased in, allowing for a transition period. During this transition period, both ENDF/B-IV l and ENDF/B-VI surveillance capsule fluence results should be reported. It is also our opinion that -

complete ENDF/B-VI based surveillance results must be used to revise the trend curves of .

10 CFR 50.61 and Regulatory Guide 1.99, Revision 2 before ENDF/BNI fluence values are required l for the calculation of pressurizer thermal shock reference temperatures (RTi q3).

The relationship of this DG with Regulatory Guide 1.99, Revision 2 needs to be clearly defined. The .

DG should provide guidance as to when vessel through-wall fluence calculations based on .

ENDF/B-VI cross-sections should take precedence over the displacement-per-atom-based  !

attenuation correlation of Regulatory Guide 1.99, Revision 2. Furthermore, the benefits analysis appears to credit the use of reduced uncertainties in determining RTi q3. Currently,10 CFR 50.61 specifies the use of the best estimate fluence and does not provide for reduction in uncertainties.

• His should be clarified and the benefits analysis adjusted, i

Additional comments on specitic sections of the DG are presented in the attached table. Should you  ;

have any questions regarding our comments, we will be pleased to discuss them with you.  ;

Very truly yours,

• I 4

[ J '

i i RED /GT/ dim  ;

Attachment:

(1) Additional Comments on Draft Regulatory Guide DG-1025 f cc: D. A. Brune, Esquire ,

J. E. Silberg, Esquire .

R. A. Capra, NRC D. G. Mcdonald, Jr., NRC '

T. T. Martin, NRC P. R. Wilson, NRC R. I. Mel.can, DNR J. H. Walter, PSC i W. H. Rasin (NUMARC)  ;

ATI'ACIIMENT (1)

g. k ADDITIONAL COMMENTS ON DRAIT REGULATORY GUIDE i

No. Pace Line Comments

1. 4 7-12 This specification of the acceptance criteria for agreement of fluence  ;

analysis with benchmark measurements belongs in 10 CFR 50.61, not  ;

here.

2. 5 8 Accounting for axial and radial water density distributions is ,

appropriate in the active core region but is probably not necessary in the region between the core shroud and core support barrel, and is -

unnecessary in the downcommer region where coolant temperature is essentially constant. This should be clarified.

i

3. 5 19 Minor changes ta cross-sections of minor constituents should not require any licensac action. Cross-section changes should be assessed  :

on their effect on the accuracy of the embrittlement trend curves of 10 CFR 50.61 and Regulatory Guide 1.99, Revision 2.

-l

4. 10 36 A clear definition of " spectral lead factor" and its application are t needed. Its relation to the attenuation function defined in  :

Regulatory Guide 1.99, Revision 2 should be clarified. i

5. 13 16- 18 ENDF/B-VI cross-sections should not be mandated for vessel fluence I

calculated from ex-vessel (cavity) dosimetry. ENDF/B-IV ~ cross-sections, will provide conservative (higher) fluences to be calculated at the vessel inner wall,1/4 T, or 3/4 T locations. This should be clarified.

6. 17,18 30-36,1-3 '/his discussion is confusing. Combination of the fluence uncertainty j '

with the best-estimate fluence is inconsistent with 10 CFR 50.61, which specifies use of the best-estimate fluence and a margin term ,

that accounts for fluence and other uncertainties. Delete the last two  :

sentences of the paragraph.

I

7. 18 7 The discussion of this section needs to be rearranged to differentiate requirements for existing surveillance capsule dosimetry from ,

requirements for dosimetry that will supplement the original capsule dosimetry. M ost of Section 2 consists of considerations ;for new/ updated / replacement dosimetry.

1

]

-I l

i

- -