ML20040E175
| ML20040E175 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 01/29/1982 |
| From: | Bordine T CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8202030218 | |
| Download: ML20040E175 (8) | |
Text
'
)
a x
Consumets Power company-Generet offices: 212 West Mechen Avenue. Jackson, MI 4920? * (517) 788-0660 January 29,.1982 9
0 gg,CTiW g1982" Q 4}
g l
Dennis M Crutchfield, Chief g
u Operating Reactors Branch.No 5 c)
Nuclear Reactor Regulation j
US Nuclear Regulatory Commission g
g' Washington, DC 20555 b
DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PLANT - REACTOR VESSEL CRITICALITY, C00LDOWN, HEATUP AND HYDROTEST LIMITATIONS Consumers Power Company, by letter dated September 18, 1981, submitted a Technical Specification Change Request to revise the Big Rock Point reactor ves s l pressure-temperature limits. NRC letter dated December 29, 1981 found the proposed revisions unacceptable. The letter enclosed comments intended for use as guidance in preparing an amended proposal. On January 8, 1982, Consumers Power Company requested and received from the staff a Technical Specification change permitting the use of the pressure-temperature limits specified in our September 18, 1981 submittal to provide for a return to power operation of the Big Rock Point Plant. The January 8, 1982 amendment permits use of the limits until the plant is shutdown for our refueling outage.
It is the intent of this letter to justify continued use of our reactor vessel limits as proposed in the September 18, 1981 submittal.
A review of the comments and guidance provided by the staff in the December 29, 1981 letter has been conducted. A review has also been performed of the documents and data used to support our Technical Specification proposal.
Based upon these reviews as well as noted data from several telephone confer-ence calls with NRC staff representatives, we have concluded that the NRC response is not a satisfactory bases for either evaluating the proposed pressure-temperature limits or for providing revised limits. We are confident that the following rationale will adequately explain the bases for our proposed reactor vessel pressure-temperature limits in order to provide for and expedite issuance of the staffs Safety Evaluation Report and subcequent amendment to our operating license.
0\\
oc0182-0017a142 D
8202030218 820129 PDR ADOCK 05000155
.p PDR
Dennis M Crutchfield, Chief 2
Big Rock Point Plant Reactor Vessel Criticality January 29, 1982 BACKGROUND The reactor vessel pressure-temperature are governed by 10 CFR 50, #ppendix G.
That Appendix is in the state of revision. One of the primary areas of impact of the proposed revision is BWR limits. Some uncertainty may perhaps still exist with respect to how the revision will read for BWRs. The NRC positica is the fact that it seeks to impose PWR data on Big Rock Point. The plant operates at about 582 F.
PWRs operate in the 540 F range. This yields a significant penalty of perhaps another 30 F on operating temperature.
In drafting pressure-temperature limits for Big Rock Point, Consumers Power Company informally sought and received guidance from the NRC on how these limits would be imposed for low pressure critical operation. Those potential misunderstandings being eliminated, the real focus of attention and contention was where it was expected to be.
The issue involved how to project radiation damage as a function of fluence from surveillance capsule data. This issue is of greater concern in BWRs than PWRs because of various parameters and controls associated with the operating environment.
The projection of radiation damage can be very inaccurate because of data scatter associated with the measurement of flux monitor activation and the calculation of the neutron dosimetry as well as the data scatter associated with Charpy tests which roughly reflect energy absorption of irradiated test specimens as a function of temperature. Operating pressure-temperature limits are also a strong function of the unirradiated reference temperature (RT NDT to which radiation effects are added.
Consumers Power Company believes that the initial (unirradiated) reference temperature and the radiation-induced shift of the reference temperature must be considered together for purposes of evaluating Charpy data and drawing realistic operating plant pressure-temperature limits.
For reactor vessels of high upper shelf welds with no drop weight specimens, the NRC Branch Tech-nical Position 5.2 is judged to impose a very unrealistic initial reference temperature. The assumption of a Branch Technical Position initial RTNDT along with shifts from bounding Charpy data curves can result in overly conservative operating limits which could perhaps compromise the ability of a BWR to perform inservice leak testing or hydrotests.
The change in emphasis for NSSS hydrostatic testing temperature limits will produce a significant impact on test performance time.
The increase, pending resolution of this issue, ranges from 40 F to 100 F (based on our submittal and NRC proposed temperature limits) in required water temperature and is the main contributor. This increase is due to the change from water temperature of approximately 175 F to a vessel metal temperature of about 206 F which would require at least 215 F water temperature. With an optimistic recirculation pump heat-up rate estimate of 4 F/hr the hydrostatic test would take from ten hours to twenty-five hours extra as a minimum. The NRC proposed onerous NSSS hydrostatic test limits will therefore contribute to a significant decrease in plant availability.
oc0182-0017a142
r Dennis M Crutchfield, Chief 3
Big Rock Point Plant Reactor Vessel Criticality January 29, 1982 BIG ROCK SURVEILLANCE TEST DATA Table 1 reflects the 30 ft-lb Charpy test data for weld metal specimens associated with the Big Rock Point reactor vessel surveillance program in six states of irradiation. Each number in the table represents an estimate of the 30 f t-lb Charpy test temperature by drawing a curve of some shape through eight to twelve (8 to 12) data points. The four columns represent four attempts to estimate the 30 ft-lb temperature value. The first column is simply a straight line through the middle of the data. The second curve is a worst case estimate assuming a typical Charpy shape through the data.
westinghouse estimated the values for all tested capsules in column three.(y)
TheNavalResearchLaboraty3yestimatedthetemperaturesforthefourcapsules it tested per column four From Table 1, it is clear that thT8Charpy curves f f8theugirradiatedcongf-tion and for fluences of 1.5 x 10 n/cm, 7.1 x 10 n/cm and 2.27 x 10 2
n/cm are fairly well defined because all four estimates of the 30 fgglb 2
temperature are very similar. However, Charpy data for the 2.3 x 10 n/cm condition were very scattered and the difference between the straight line and worst case estimates reflects that.
It is reasonably clear from Table 1 that the Westinghouse estimate is based upon an average type of curve and the NRL value is a bound or worst case value.
Table 2 merely reflects the 30 ft-lb shifts associated with the estimates of Table 1.
What one gleans from the Table 2 values depends upon whether one is interested in averages or worst case. The average trend (straight line or Westinghouse column) implies a flattening out of damage as a function of fluence. The bounding trend does not reflect this flattening.
It would appear that a smoother plot might be made of the data if the 140 F was actual-ly somewhat higher. However, that point is made from a fairly well defined curve whereas the 190*F and 230*F points are from badly scattered data.
Table 3 is a plot of twenty three welds for which Charpy curves and drop weight specimens were available. The data were collected by EPRI to show that the NRC Branch Technical Position 5.2 may reflect an appropriate low upper (1) S E Yanichko, S L Anderson, R P Shagan and R G Lott, " Analysis of Capsule 125 From the Consumrs Power Company Big Rock Point Nuclear Plant Reactor Vessel Radiation Surveillance Program (WCAP-9794)," Pittsburgh, PA, Westinghouse Electric Corporation, Ecptember 1980. Topical Report on EPRI Research Project 1021-3 (2) Serpan,
- 2, and Watson, H E, " Mechanical Property and Neutron Spectral Analyses of the Big Rock Point Reactor Pressure Vessel," Nuclear Engineering and Design, Volume II, No 3, April 1970.
oc0182-0017a142
I Dennis M Crutchfield, Chief 4
Big Rock Point Plant Reactor Vessel Criticality January 29, 1982 shelf weld criteria yet is unrealistic for high upper shelf welds. Big Rock Point weld material is clearly high upper shelf material. However, the Big Rock Point vessel was fabricated before there was an ASTM standard for dropweight testing.
Since the ASME Code Section III uses dropweight data to establish an initial RT Big Rock Point welds do not have an RT in the ASME Code sense. However,NDT,theBigRockPointweldmaterialhasaweId ND material Charpy curve with a 30 ft-lb energy of -70*F.
From Table 3 one may determine that, with a high degree of assurance, if a dropweight specimen had existed, it would have registered a NDTT of no higher than -50*F and thus the RT w uld have been no higher than -50*F since the 50ft-lb Charpy tempera-NDI ture value does not exceed 0*F.
A bounding curve of Table 3 data suggests
{
that the Branch Technical Position is at least 50 F overconservative for a Big Rock Point reactor vessel weld.
Capsule 125 is essentially on the vessel wall at what is ' judged to be the location of maximum fluence. No lead factor is assumed. That is, fluence determined by the flux monitors is taken as wall fluence. The flucoce deter-mined was 94.5 percent that projected for that point in time by surveillance capsules removed in the 1960s. Employing the higher estimated fluences, one woulggdetergine that capsule 125 was pulled at 8.49 EFPY at a fluence of 2.40 x }g /cmn/gm'. Presently, (end of 1981), the flueng is egtimated to be 2.85 x 10 n
at 10.06 EFPY. The fluence of 4.5 x 10 n/cm to which the curves are to be projected is consistent with an EFPY of 5.8 beyond 1981.
REVIEW OF NRC COMMENTS ON BIG ROCK PRESSUR,E-TEMPERATURE LIMITS The NRC comments via the December 19, 1981 letter appear to be more oriented toward attacking the " saturation" issue rather than dealing with the data and discussion in our September 18, 1981 submittal.
Consumers Power Company is interested in using test data from Big Rock Point surveillance capsules and initial RT data (not available in the Big Rock Point surveillance program)
NDT from high upper shelf welds aimilar to those su the Big Rock Point vessel. We see no value to proving or disproving saturation nor in establishing new trend curves. We contend that the data from the surveillance program is sufficient to obviate PWR data points from other vessels.
ConsumersPowerCompanyjgesnogcontendthattheRTNDT shift of 135 F applies to a fluence of 4.5 x 10 n/cm. However,weggvecogeludedthat135*Fisa very reasonable estimate of shift for 3.11 x }g /cm.n/gm which is the 1/4 T fluence for an inner wall fluence of 4.5 x 10 n
Table 2 reflects on that consideration.
It appears rather irregular to classify shifts as noncredible data points. A review of Table 2 indicates that the 170*F data point reflects a shift deter-mined by drawing a Charpy sggped cgrve through ggdly sgattered data. No trend curves through the 2.3 x 10 n/cm or 10.7 x 10 n/cm capsule data would appear to be any more credible than any other.
oc0182-0017a142
Dennis M Crutchfield, Chief 5
Big Rock Point Plant Reactor Vessel Criticality January 29, 1982 CONCLUSION Prer,ently, Consumers Power Company is attempting to project pressure-temperattare limits based upon surveillance data from the Big Rock Point surveillance capsules. Ofconcernisthedetermingiono{theinitialRTA review of b ble shift associated with a 1/4 T fluence of 3.11 x 10 n/cm.
2 indicates that on an average approximation basis, 135 F is a very reasonable estimate of shift. On a worst case basis, one could perhaps arrive at a shift of 195 F.
Consideration of Table 3 suggests that the initial RT is no greaterthan-50*andmorelikely-60Fratherthanthe0*Fimposedbythe ND Branch Technical Position. Nevertheless, our proposed September 18, 1981 submittal assumes the conservative 0 F reference temperature. However, it does not appear reasonable to use 0* for an initial RT and a worst case NDT shift of 195*F.
It is more reasonable to employ a mean with a bound. That is, the equivalent irradiated RT would be 0* + 135*F = 135*F or -60 F +
195 F = 135*F.
ThismethodisaNoconsistentwithpracticesutilizedbyNSSS I
vendors. Thus, the basis for our pressure-temperature limits is supported by this approach.
It is reiterated that the test data should be the focus of attention, No attempt is made to prove saturation, discount data, use PE data for L%4 applications, develop new trends or to bound all available results. On this basis, the Consumers Power Company September 18, 1981 submittal is reasonable and appropriate.
It should also be noted that the cover letter to our September 18, 1981 Change Request was revised per telephone conference call of October 26, 1981 with Mr W Paulson of your staff. Our submittal specifies that " administrative controls will be established requiring all points in the reactor vessel and stet.m drum to be greater than the required temperature limit." Since there are fourteen thermocouples on the vessel and six on the steam drum, it will not be necessary to assure that all are greater than the required temperature, thereby allowing for thermocouple failure. Access limitations should failure occur, necessitate the commitment change.
,/
" ')
e
<u Thomas C Bordine Staff Licensing Engineer CC Administrator, Region III, USNRC NRC Resident Inspector-Big Rock Point pages oc0182-0017a142 i
TABLE 1 BIG ROCK POINT SURVEILLANCE CHARPY IMPACT TEST 30 FT-LB DATA
SUMMARY
FOR WELD SPECIMENTS 1
Fluence Charpy 30 Ft-Lb Temperatures
- F n/cm 1 Mev Straight Line Worst Case Westinghouse
_NRL Unirradiated
-70
-70
-70
-70 I
1.5 x 10
-10
-10
-15
-13 18 7.1 x 10 65 65 65 65 19 2.27 x-10 65 70 65 N/A 19 2.3x 10 65 120 60 120 19 10.7 x 10 80 160 100 160 f
i I
l i
nu0182-0017c142
4 TABLE 2~
BIG ROCK POINT SURVEILLANCE CHARPY IMPACT TEST DATA 30 FT-LB SHIFTS FOR WELD SPECIMENS Fluence Charpy 30 Ft-Lb Termperature Shifts
- F n/cm 1 Mev-Straight Line Worst Case Westinghouse NRL 18 1.5 x 10 60 60 55 55 I
7.1 x 10 135 135 135 135 19 2.27 x 10 135 140 135 N/A 19 2.3 x 10 135 190 130 190 (3.11 x 1019)*'
135 (195)*
135 (195)*
10.7 x 10 '
150 230 170 230
- (reference ' conclusion - interpolation point) 19 2
j 1/4 T fluence for an inner wall fluence of 4.5 x 10 n/cm l
l l
}
l nu0182-0017c142 i
J O
9
,8 9
4 E
h
.8]-
3 2
a y
x i
N s-m, e
s a5 8
o
'S mmI e
w
- a S
9 y
9/-
O o
t 1
o 5
E 8
8 a
Y.g!
.o s
s 8
E$
ER 8
E 2
8 8
o P
'sm x4i e
es B
$8 8
y 8
g gT i
gk
..