2010-2283. Alternate Fracture Toughness Requirements for Protection Against Pressurized Thermal Shock Events; Correction

AGENCY:

Nuclear Regulatory Commission.

ACTION:

Final rule; correction.

SUMMARY:

This document corrects a rule that appeared in the Federal Register on January 4, 2010 (75 FR 13), that amends the NRC's regulations to provide alternate fracture toughness requirements for protection against pressurized thermal shock (PTS) events for pressurized water reactor (PWR) pressure vessels. This document is necessary to correct formatting and typographical errors in paragraph (g).

DATES:

The correction is effective February 3, 2010, the date the original rule becomes effective.

FOR FURTHER INFORMATION CONTACT:

Michael T. Lesar, Chief, Rulemaking and Directives Branch, Office of Administration, Nuclear Regulatory Commission, Washington, DC 20555-0001, telephone [phone], e-mail [e-mail].

SUPPLEMENTARY INFORMATION:

In FR doc. E9-31146, published on January 4, 2010, make the following correction:

§ 50.61a

[Corrected]

1. On page 27, paragraph (g) of § 50.61a is corrected to read as follows:

(g) Equations and variables used in this section.

where:

P [wt-&%] = phosphorus content

Mn [wt-%] = manganese content

Ni [wt-%] = nickel content

Cu [wt-%] = copper content

A = 1.140 × 10⁻⁷ for forgings

A = 1.451 × 10⁻⁷ for plates

A = 1.417 × 10⁻⁷ for welds

B = 102.3 for forgings

B = 102.5 for plates in non-Combustion Engineering manufactured vessels

B = 135.2 for plates in Combustion Engineering vessels

B = 155.0 for welds

φt_e = φt for φ ≥ 4.39 × 10¹⁰ n/cm²/sec

φt_e = φt × (4.39 × 10¹⁰/φ)^0.2595 for φ < 4.39 × 10¹⁰ n/cm²/sec

where:

φ [n/cm²/sec] = average neutron flux

t [sec] = time that the reactor has been in full power operation

φt [n/cm²] = φ × t

f(Cu_e,P) = 0 for Cu ≤ 0.072

f(Cu_e,P) = [Cu_e−0.072]^0.668 for Cu > 0.072 and P ≤ 0.008

f(Cu_e,P) = [Cu_e−0.072 + 1.359 × (P−0.008)]^0.668 for Cu > 0.072 and P > 0.008

where:

Cu_e = 0 for Cu ≤ 0.072

Cu_e = MIN (Cu, maximum Cu_e) for Cu > 0.072

maximum Cu_e = 0.243 for Linde 80 welds

maximum Cu_e = 0.301 for all other materials

g(Cu_e,Ni,φt_e) = 0.5 + (0.5 × tanh {[log₁₀ (φt_e) + (1.1390 × Cu_e)−(0.448 × Ni)−18.120]/0.629}

Equation 8: Residual (r) = measured ΔT₃₀−predicted ΔT₃₀ (by Equations 5, 6 and 7)

Equation 10: Maximum credible heat-average residual = 2.33σ/n^0.5

where:

where:

n = number of surveillance data points (sample size) in the specific data set

σ = standard deviation of the residuals about the model for a relevant material group given in Table 5.

where:

m is the slope of a plot of all of the r values (estimated using Equation 8) versus the base 10 logarithm of the neutron fluence for each r value. The slope shall be estimated using the method of least squares.

se(m) is the least squares estimate of the standard-error associated with the estimated slope value m.

where:

r is defined using Equation 8 and σ is given in Table 5

Table 1—PTS Screening Criteria

Product form and RTMAX-X values	RTMAX-X limits [°F] for different vessel wall thicknesses 6 (TWALL)
	TWALL ≤ 9.5 in.	9.5 in. < TWALL ≤ 10.5 in.	10.5 in. < TWALL ≤ 11.5 in.
Axial Weld—RTMAX-AW	269	230	222
Plate—RTMAX-PL	356	305	293
Forging without underclad cracks—RTMAX-FO 7	356	305	293
Axial Weld and Plate—RTMAX-AW + RTMAX-PL	538	476	445
Circumferential Weld—RTMAX-CW 8	312	277	269
Forging with underclad cracks—RTMAX-FO 9	246	241	239
6 Wall thickness is the beltline wall thickness including the clad thickness.
7 Forgings without underclad cracks apply to forgings for which no underclad cracks have been detected and that were fabricated in accordance with Regulatory Guide 1.43.
8 RTPTS limits contribute 1×10−8 per reactor year to the reactor vessel TWCF.
9 Forgings with underclad cracks apply to forgings that have detected underclad cracking or were not fabricated in accordance with Regulatory Guide 1.43.

Table 2—Allowable Number of Flaws in Welds

Through-wall extent, TWE [in.]		Maximum number of flaws per 1,000-inches of weld length in the inspection volume that are greater than or equal to TWEMIN and less than TWEMAX
TWEMIN	TWEMAX
0	0.075	No Limit.
0.075	0.475	166.70.
0.125	0.475	90.80.
0.175	0.475	22.82.
0.225	0.475	8.66.
0.275	0.475	4.01.
0.325	0.475	3.01.
0.375	0.475	1.49.
0.425	0.475	1.00.
0.475	Infinite	0.00.

Table 3—Allowable Number of Flaws in Plates and Forgings

Through-wall extent, TWE [in.]		Maximum number of flaws per 1,000 square-inches of inside surface area in the inspection volume that are greater than or equal to TWEMIN and less than TWEMAX. This flaw density does not include underclad cracks in forgings
TWEMIN	TWEMAX
0	0.075	No Limit.
0.075	0.375	8.05.
0.125	0.375	3.15.
0.175	0.375	0.85.
0.225	0.375	0.29.
0.275	0.375	0.08.
0.325	0.375	0.01.
0.375	Infinite	0.00.

Table 4—Conservative Estimates for Chemical Element Weight Percentages

Materials	P	Mn
Plates	0.014	1.45
Forgings	0.016	1.11
Welds	0.019	1.63

Table 5—Maximum Heat-Average Residual [°F] for Relevant Material Groups by Number of Available Data Points (Significance Level = 1%)

Material group	σ [°F]	Number of available data points
		3	4	5	6	7	8
Welds, for Cu > 0.072	26.4	35.5	30.8	27.5	25.1	23.2	21.7
Plates, for Cu > 0.072	21.2	28.5	24.7	22.1	20.2	18.7	17.5
Forgings, for Cu > 0.072	19.6	26.4	22.8	20.4	18.6	17.3	16.1
Weld, Plate or Forging, for Cu ≤ 0.072	18.6	25.0	21.7	19.4	17.7	16.4	15.3

Table 6—T_MAX Values for the Slope Deviation Test (Significance Level = 1%)

Number of available data points (n)	TMAX
3	31.82
4	6.96
5	4.54
6	3.75
7	3.36
8	3.14
9	3.00
10	2.90
11	2.82
12	2.76
13	2.72
14	2.68
15	2.65

Dated at Rockville, Maryland, this 29th day of January 2010.

For the Nuclear Regulatory Commission.

Michael T. Lesar,

Chief, Rulemaking and Directives Branch, Division of Administrative Services, Office of Administration.