Regulatory Guide 1.99

Effects of Residual Elements on Predicted Radiation Damage to Reactor Vessel Materials

ML12298A136
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Issue date:	04/30/1977
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RG-1.099, Rev. 1
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RE,vision 1 U.S. NUCLEAR REGULATORY COMMISSION A priI 1977

)REGULATORY GUIDE

OFFICE OF STANDARDS DEV9LOPMENT

REGULATORY GUIDE 1.99 EFFECTS OF RESIDUAL ELEMENTS ON PREDICTED RADIATION DAMAGE

TO REACTOR VESSEL MATERIALS

A. INTRODUCTION

1. Paragraph II.H of Appendix G defines the beltline in terms of a predicted adjustment of General Design Criterion 31, "Fracture Prevention reference temperature at end of service life in excess of Reactor Coolant Pressure Boundary," of Appen- of 500F; paragraphs III.C and IV.B specify the ad- dix A, "General Design Criteria for Nuclear Power ditional test requirements for beltline materials that Plants," to 10 CFR Part 50, "Licensing of Produc- supplement the requirements for reactor vessel tion and Utilization Facilities," requires, in part, that materials generally.

the reactor coolant pressure boundary be designed with sufficient margin to ensure that, when stressed 2. Paragraph II.C.3 of Appendix H establishes the under operating maintenance, testing, and required number of surveillance capsules on the basis postulated accident conditions, (1) the boundary of the predicted adjusted reference temperature at the behaves in a nonbrittle manner and (2) the end of service life. In addition, withdrawal of the first probability of rapidly propagating fracture is capsule (when four or more are required) is to occur minimized. Appendix G, "Fracture Toughness Re- when the predicted adjustment of reference quirements," and Appendix H, "Reactor. Vessel temperature is approximately 50°F or at one-fourth Material Surveillance Program Requirements," of the service life, whichever is earlier.

which were added to 10 CFR Part 50 effective August

16, 1973, to implement, in part, Criterion 31, neces- 3. Paragraph IV.C of Appendix G requires that sitate the prediction of the amount of radiation vessels be designed to permit a thermal annealing

)* damage to the reactor vessel of water-cooled power treatment if the predicted value of adjusted reference

• reactors throughout its service life. temperature exceeds 200°F during their service life.

This guide describes general procedures acceptable 4. Paragraph II.B of Appendix H incorporates to the NRC staff as an interim basis* for predicting ASTM E185-73 by reference. Paragraph 4.1 of the effects of the residual elements copper and ASTM E185-73 requires that the materials, to be phosphorus on neutron radiation damage to the low- placed in surveillance be those that may limit opera- alloy steels currently used for light-Water-cooled reac- tion of the reactor during its lifetime, i.e., those ex-

• • tor vessels. The Advisory Committee on Reactor pected to have the highest adjusted reference Safeguards has been consulted concerning this guide temperature or the lowest Charpy upper-shelf energy and has concurred in the regulatory position. at end of life. Both measures of radiation damage must be considered.

B. DISCUSSION

5. Paragraph V.B of Appendix G describes the The principal examples of NRC requirements that basis for setting the upper limit for pressure as a func- necessitate prediction of radiation damage are: tion of temperature during heatup and cooldown for a given service period in terms of thepredicted value

• Research and construction experience with low-residual-element of the adjusted reference temperature at the end of compositions of these steels is accumulating rapidly and is ex- the service period.

pected to provide a firm basis for acceptable procedures in the near future. The two measures of radiation damage used in this

"*Lines indicate substantive changes from previous issue. guide are obtained from the results of the Charpy V-

USNRC REGULATORY GUIDES Comments should be sent to the Secretary of the Commission, US. Nuclear Regu- latory Commission, Washington, D.C. 20555, Attention: Docketing and Service Regulatory Guides are issued to describe and make available to the public methods Branch.

acceptable to the NRC staff of implementing specific parts of the Commission's regulations, to delineate techniques used by the staff in evaluating specific problems The guides are issued in the following ten broad divisions:

or postulated accidents, or to provide guidance to applicants. Regulatory Guides are not substitutes for regulations, and compliance with them is not required. 1. Power Reactors 6. Products Methods and solutions different from those set out in the guides will be accept- 2. Research and Test Reactors 7. Transportation able if they provide a basis for the findings requisite to the issuance or continuance 3. Fuelsand Materials Facilities

8. Occupational Health

4. Environmental and Siting 9. Antitrust Review of a permit or license by the Commission. 5. Materials and Plant Protection 10. General Comments and suggestions for improvements in these guides are encouraged at all Requests for single copies of issued guides (which may be reproduced) or for place- times, and guides will be revised, as appropriate, to accommodate comments and ment on an automatic distribution list for single copies of future guides in specific to reflect new information or experience. This guide was revised as a result of divisions should be made in writing to the US. Nuclear Regulatory Commission, substantive comments received from the public and additional staff review. Washington, D.C. 20555, Attention: Director. Division of Document Control.

notch impact test. Appendix G to 10 CFR 'Part 50 re- position when the copper content is about 0.15%. The quires that a full curve of absorbed energy versus effects of irradiation temperature on decrease in shelf temperature be obtained through the ductile-to- energy should be considered qualitatively similar to brittle transition temperature region. The latter is those cited for the adjustment of referencej located by the reference temperature, RTNDT, which temperature.

is defined in paragraph II.F of Appendix G. The

"shift" of the adjusted reference temperature is Sensitivity to neutron embrittlement may be af- defined in Appendix G as the temperature shift in the fected by other residual elements such as vanadium Charpy V-notch curve for the irradiated material and by deoxidation practice, as indicated by the relative to that for the unirradiated material, findings of current research. In predicting radiation measured at the 50-foot-pound energy level or damage for materials that differ in chemical content measured at the 35-mil lateral expansion level, or deoxidation practice from those that make up the whichever temperature shift is greater. In using data base, such findings should be considered. Other published data that report only the temperature shift residual elements, notably sulfur, impair the initial measured at the 30-foot-pound energy level, it has Charpy shelf energy of these materials, and their con- been assumed herein that the adjustment of the tent should be kept low. Clearly, it is the remaining reference temperature is equal to the 30-foot-pound toughness at end of life or at some other critical shift. period that is important. Such toughness may be The second measure of radiation damage is the given in terms of the margin between the operating decrease in the Charpy upper-shelf energy level. In temperature (nominally 550°F) and the limiting the absence of a standard definition, the upper-shelf temperature based on toughness. A margin of 200

energy is defined herein as the average energy value degrees is desirable to permit safe management of for all specimens whose test temperature is above the system transients. At full power, the limiting upper end of the transition temperature region. Nor- temperature based on toughness is generally 150-200

mally, at least three specimens should be included; degrees above RTNDT; hence, the latter should not more specimens should be included when the shelf exceed 150-2001F at end of life. This limit also avoids

,level appears to be marginal. However, if specimens the problems of providing for annealing, per are tested in sets of three at each test temperature, the paragraph IV.C of Appendix G. The levels of set having the highest average may be regarded as residual elements such as copper, phosphorus, sulfur, defining the upper-shelf energy. and vanadium that are required to achieve the limit of 200'F adjusted reference temperature at end of life The measure of fluence used herein is the number in a given reactor vessel will depend on the initial of neutrons per square centimeter (E>I MeV). An as- values of RTNDT of the beltline materials and on tle"

sumed fission-spectrum energy distribution was used predicted fluence at the particular locations in the in calculating the fluence for most of the data base.* vessel where the materials are used.

However, for application to a reactor vessel, the calculated spectrum is used to predict fluence at a When surveillance data from the reactor in ques- given location in the wall. This procedure is not in- tion become available, the weight given to it relative tended to preclude future use of data that are given in to the information in this guide should depend on the terms of neutron damage fluence. credibility of the surveillance data as judged by the following criteria:

As used herein, references to "% Cu" and "% P"

mean the weight percent of copper and phosphorus as measured in the surveillance program per ASTM 1. Materials in the capsule should be those judged most likely to be controlling with regard to radiation E185-73. However, if such results are not available, damage according to the provisions of this guide.

the results of a product analysis may be used.

Use of the procedures for prediction of radiation 2. Scatter in the Charpy data should be small damage given in the regulatory position should be enough to avoid large uncertainty in curve fitting.

limited to irradiation at 550 +/-251F, because temperature is important to damage recovery proces- 3. The change in yield strength should be consis- ses. As a guideline, irradiation at 4501F has been tent with the shift in the Charpy curve.

shown to cause twice the adjustment of reference temperature and irradiation at 650°F, about half the 4. The relationship to previous isurveillance data ladjustment produced by irradiation at 550OF for the from the same reactor should be consistent with the fluence levels and the steels cited in the regulatory normal trends of such dat

a. I

• The data base for this guide is that given by Spencer H. Bush,

"Structural Materials for Nuclear Power Plants." 1974 ASTM Gil- lett Memorial Lecture, published in ASTM Journal of Testing and 5. The surveillance data for the correlation Evaluation, Nov. 1974, and its addendum, "Radiation Damage in monitor material in the capsule should fall within the Pressure Vessel Steels for Commercial Light-Water Reactors." scatter band of the data base for that material.

1.99-2

C. REGULATORY POSITION

(3) The expression for A is given in terms of fluence as measured by units of n/cm2 (E > 1 MeV);

1. When credible surveillance data from the reac- however, the expression may be used in terms of tor in question are not available, prediction of fluence as measured by units of neutron damage neutron radiation damage to the beltline of reactor fluence, provided the constant 1019 n/cm2 (E> 1 vessels of light water reactors should be based on the MeV) is changed to the corresponding value of following procedures. neutron damage fluence.

(4) Application of these procedures to materials having chemical content beyond that represented by the current data base should be a. Reference temperature should be adjusted as justified by submittal of data.

a function of fluence and residual element content in accordance with the following expression, within the 2. When credible surveillance data from the reac- limits below and in paragraph l.c. tor in question become available, they may be used to represent the adjusted reference temperature and the A = [40 + 1000(% Cu - 0.08) Charpy upper-shelf energy of the beltline materials at

+ 5000 (% P - 0.008) ] [f/ 1019] the fluence received by the surveillance specimens.

where a. The adjusted reference temperature of the A = predicted adjustment of reference beltline materials at other fluences may be predicted temperature, OF. by:

f = fluence, n/cm2 (E>l MeV). (1) extrapolation to higher or lower fluences from credible surveillance data following the slope of

% Cu = weight percent of copper. the family of lines in Figure 1 or If % CuK 0.08, use 0.08.

(2) a straight-line interpolation between credi-

% P = weight percent of phosphorus. ble data on a logarithmic plot.

If % P5K0.008, use 0.008.

b. To predict the decrease in upper-shelf energy If the value of A obtained by the above expression of the beltline materials at fluences other than those exceeds that given by the curve labeled "Upper received by the surveillance specimens, procedures Limit" in Figure 1, the "Upper Limit" curve should similar to those given in paragraph 2.a may~be fol- be used. If % Cu is unknown, the "Upper Limit" lowed using Figure 2.

curve should be used.

3. For new plants, the reactor vessel beltline As illustrated in Figure 1 for selected copper and materials should have the content of residual ele- phosphorus contents, the above expression should be ments such as copper, phosphorus, sulfur, and considered valid only for A >50°F and for f( 6 x 10'9 vanadium controlled to low levels. The levels should n/cm2 (E > 1 MeV). be such that the predicted adjusted reference temperature at the 1/4T position in the vessel wall at b. Charpy upper-shelf energy should be as- end of life is less than 2000F.

sumed to decrease as a function of fluence and copper content as indicated in Figure 2, within the limits

D. IMPLEMENTATION

listed in paragraph l.c. Interpolation is permitted.

The purpose of this section is to provide informa- c. Application of the foregoing procedures tion to applicants and licensees regarding the NRC

should be subject to the following limitations:. staff's plans for utilizing this regulatory guide.

(1) The procedures apply to those grades of This guide reflects current regulatory practice.

SA-302,. 336, 533, and 508 steels having minimum Therefore, except in those cases in which the appli- specified yield strengths of 50,000 psi and under and cant proposes an acceptable alternative method for to their welds and heat-affected zones. complying with specified portions of the Commis- sion's regulations, the positions described in this

(2) The procedures are valid for a nominal ir- guide will be used by the NRC staff as follows:

radiation temperature of 550°F. Irradiation below

5251F should be considered to produce greater 1. The method described in regulatory positions damage, and irradiation above 5751F may be con- C. 1 and C.2 of this guide will be used in evaluating all sidered to produce less damage. The correction factor predictions of radiation damage called for in Appen- used should be justified. dices G and H to 10 CFR Part 50 submitted on or

1.99-3

after June 1, 1977; however, if an applicant wishes to plications docketed on or after June 1, 1977;

use the recommendations of regulatory positions C. 1 however, if an applicant whose application for con- and C.2 in developing submittals before June 1, 1977, struction permit is docketed before June 1, 1977, j the pertinent portions of the submittal will be wishes to use the recommendations of regulatory'

evaluated on the basis of this guide. position C.3 of this regulatory guide in developing submittals for the application, the pertinent portions

2. The recommendations of regulatory position of the application will be evaluated on the basis of C.3 will be used in evaluating construction permit ap- this guide.

4

1.99-4

7w A = [40 + 1000 (% Cu - 0.08) + 5000 (% P - 0.008)] [f/10191 1)

400

)-ýPl

,, 300

0

C.

E

0 200

4- IL%

I

-.

i i i L l i i i ~ m- i i 1 11 11am 1 1 1 i i i i I I I I I III~..~~IIIIIIIIIIIIiIIIjTIIII[III

i i i i i i ii H HHHHH i i i i i i ! i H HHHHHHi .... IILJ.* II!I I i II I i IIBI

0 100

E

,JI 5-

• 50

0.25;M020 /, rz z0.15% Cu- 0.1( IaI/ f C.,

1.

I =I LOWER LIMIT

a,  % Cu = 0.08

% P = 0.008

17

2X10 4 6 8. 10 1 8 2 4 6 8 1019 2 4 6 FLUENCE, n/cm 2 (E > 1MeV)

Figure 1 Predicted Adjustment of Reference Temperature, "A", as a Function of Fluence and Copper Content.

For Copper and Phosphorus Contents Other Than Those Plotted, Use the Expression for "A" Given on the Figure.

~~~U.,3UU .

- 20 0.25

-- -------- 0.20 - 0.15-

0.15 0.10-- W

wL IT

C,"

___ O. 10---.05 ---

I Z

Aftk --

26 11 8 4 08 6 8 1092 4 6 FLUENCE, n/cm2 (E > 1MeV)

Figure 2 Predicted Decrease in Shelf Energy as a Function of Copper Content and Fluence.

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