ML20052B237
| ML20052B237 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 04/27/1982 |
| From: | Nichols T SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8204300199 | |
| Download: ML20052B237 (3) | |
Text
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E Mr. Harold R.
Denton, Director g
9 Office of Nuclear Reactor Regulation a
U.S.
Nuclear Regulatory Commission Washington, D.C.
20555
Subject:
Virgil C.
Summer Nuclear Station Docket No. 50/395 Steam Generator Modification
Dear Mr. Denton:
Recently, the NRC requested certain information regard-ing modifications to the Virgil C.
Summer Nuclear Station steam generators for the tube vibration problem.
Specifi-cally requested were (a) an estimate of the total time to make the modifications, (b) an estimate of the radiation field where personnel will be working, and (c) an estimate of the total radiation exposure to personnel for the modification work.
Recognizing that the modifications being considered by Westinghouse are in the design stage, information regarding any aspect can only be considered preliminary or best esti-mates.
With that understanding, SCE&G contacted Westinghouse to obtain the information requested.
For the purpose of this analysis three assumptions were made.
These assumptions are an operating history of 50% power for one year, the modification to be performed with the primary system filled and the secondary system empty, and 0% failed fuel.
With these assumptions the best estimates at this time are:
a)
Approximately three to four months required to complete the modifications, with a modification design potentially available in the latter part of 1982.
b)
Radiation environment estimated to be:
1) 5 - 15 mrem /hr. general background.
2) 1.5 - 4 rem /hr. internal to the steam generator.
3) 600 mrem /hr. inside the steam generator main feed water nozzle at the impingement plate.
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Mr. Harold Denton April 27, 1982 Page 2 c)
Approximately 150 to 175 person-rem total radiation exposure per steam generator estimated.
Specific ALARA considerations currently being investigated in an effort to reduce total exposures include in-depth pre-job planning and assessment, training of individuals utilizing full scale mock-ups, ALARA design reviews, use of automated welding equipment in high exposure areas and the development of additional techniques and tooling to reduce job specific exposures.
Westinghouse estimates a potential reduction of 25 - 50 person-rem / generator through these efforts.
As indicated in the Virgil C.
Summer Nuclear Station Final Environmental Statement (FES) S9ction 4.5.2.3, the NRC staff's occupational dose estimate utilized for the analysis of impacts on the radiation work force population is 1300 person-rems /yr. averaged over the life of the plant.
This estimate has been utilized realizing the unpredictable nature and frequency of required routine and special maintenance such as the subject steam generator repair.
Section 12.1.6.3 of the FSAR provides an estimated total annua! dose of about 400 person-rens per year associated with normal station operations.
This is discussed in Section 12.4 of the NRC's Safety Evaluation Report (SER).
The difference of these estimates provides guidance on the magnitude of average total person-rem associated with unpredictable major maintenance or modifications required.
Thus, the SER and FES have considered an annual average non-routine dose of 900 person-rems per. year in the staff assessment of the radiological impacts of station operation.
The steam generator modifications currently being considered will be accomplished in accordance with ALARA requirements.
Estimates of exposures are currently being refined but they indicate that considerably less than 900 person-rems will be required for this modi #ication.
As the FES and SER have considered the impacts associated with an annual average radiation worker exposure of 1300 person-rem, this modification considering anticipated exposures is consistent with NRC operating license evaluations.
Mr. Harold Denton April 27, 1982 Page 3 If you have additional questions, please advise us.
Very truly yours, l
T.
C.
- Nichols, Vice-President and Group Executive Nuclear Operations RBC:TCN:fjc cc:
V.
C. Summer G.
H. Fischer H.
N.
Cyrus T.
C.
Nichols, Jr.
M.
B.
Whitaker, Jr.
J.
P. O'Reilly H.
T.
Babb D.
A.
Nauman C.
L. Ligon (NSRC)
W.
A. Williams, Jr.
R.
B.
Clary O.
S. Bradham A.
R.
Koon M.
N. Browne i
G.
J.
Braddick J.
C. Ruoff 1
J.
L.
Skolds J.
B.
Knotts B.
A.
Bursey NPCF File 1
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