ML12145A013
| ML12145A013 | |
| Person / Time | |
|---|---|
| Issue date: | 04/30/1977 |
| From: | NRC/OSD |
| To: | |
| Kirk M | |
| References | |
| RG-1.099, Rev 1 | |
| Download: ML12145A013 (7) | |
Text
Retype of Next Page (1.99-3) Due to Text Illegibility 1.99-3 C. REGULATORY POSITION
- 1. When credible surveillance data from the reactor in question are not available, prediction of neutron radiation damage to the beltline of reactor vessels of light water reactors should be based on the following procedures.
- a. Reference temperature should be adjusted as a function of fluence and residual element content in accordance with the following expression, within the limits below and in paragraph l.c.
A = [40 + 1000(% Cu - 0.08)
+ 5000 (% P -0.008)] [f/1019]1/2 where A = predicted adjustment of reference temperature, °F.
f = fluence, n/cm2 (E>1 MeV).
% Cu = weight percent of copper.
If % Cu < 0.08. use 0.08.
% P = weight percent of phosphorus.
If % P < 0.008. use 0.008.
If the value of A obtained by the above expression exceeds that given by the curve labeled "Upper Limit" in Figure I, the "Upper Limit" curve should be used. If %
Cu is unknown, the "Upper Limit" curve should be used.
- b. Charpy upper-shelf energy should be as-sumed to decrease as a function of fluence and copper content as indicated in Figure 2. within the limits listed in paragraph 1.c. Interpolation is permitted.
- c. Application of the foregoing procedures should be subject to the following limitations:
(1) The procedures apply to those grades of SA-302, 336, 533, and 508 steels having minimum specified yield strengths of 50,000 psi and under and to their welds and heat-affected zones.
(2) The procedures are valid for a nominal irradiation temperature of 550°F. Irradiation below 525°F should be considered to produce greater damage and irradiation above 575°F may be considered to produce less damage. The correction factor used should be justified.
(3) The expression for A is given in terms of fluence as measured by units of n/cm² (E > I MeV) however, the expression may be used in terms of fluence as measured by units of neutron damage fluence, provided the constant 1019 n/cm2 (E > l MeV) is changed to the corresponding value of neutron damage fluence.
(4) Application of these procedures to materials having chemical content beyond that represented by the current data base should be justified by submittal of data.
- 2. When credible surveillance data from the reactor in question become available, they may be used to represent the adjusted reference temperature and the Charpy upper-shelf energy of the beltline materials at the fluence received by the surveillance specimens.
- a. The adjusted reference temperature of the beltline materials at other fluences may be predicted by:
(1) extrapolation to higher or lower fluences from credible surveillance data following the slope of the family of lines in Figure 1 or (2) a straight-line interpolation between credible data on a logarithmic plot.
- b. To predict the decrease in upper-shelf energy of the beltline materials at fluences other than those received by the surveillance specimens, procedures similar to those given in paragraph 2.a may be followed using Figure 2.
- 3. For new plants, the reactor vessel beltline materials should have the content of residual elements such as copper, phosphorus, sulfur, and vanadium controlled to low levels. The levels should be such that the predicted adjusted reference temperature at the 1/4 T position in the vessel wall at end of life is less than 200°F.
D. IMPLEMENTATION The purpose of this section is to provide information to applicants and licensees regarding the NRC staffs plans for utilizing this regulatory guide This guide reflects current regulatory practice.
Therefore, except in those cases in which the applicant proposes an acceptable alternative method for complying with specified portions of the Commission's regulations, the positions described in this guide will be used by the NRC staff as follows:
- 1. The method described in regulatory positions C.1 and C.2 of this guide will be used in evaluating all predictions of radiation damage called for in Appendices G and H to 10 CFR Part 50 submitted on or