ML090990732
| ML090990732 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 10/08/2008 |
| From: | Sacramento Municipal Utility District (SMUD) |
| To: | Donna Anderson NRC/FSME |
| Shared Package | |
| ML090830613 | List:
|
| References | |
| DPG 09-097 | |
| Download: ML090990732 (39) | |
Text
Rancho Seco Final Status Survey SummaryReport October 8, 2008 Fuel Storage Building (+) 40' El., Lower Walls Survey Unit F8121002 Prepared By: *C. *t c'n- Date: o / F'/2.WcS' FSS Engineer Reviewed By: .- Date: ,o /o to Lead FSS Engineer Approved By: Date:______
Dismantlement Superintendent, Radiological
FINAL STATUS SURVEY
SUMMARY
REPORT Survey Unit:
F8121002, Fuel Storage Building (+) 40' El., Lower Walls Survey Unit
Description:
Operating History: The reinforced concrete structure contained the spent fuel pool and supporting systems. The building contained three main elevations including the pool.
Residual radioactive material was known to be present on all levels of the interior of the building. Operating records and the HSA document several events with the potential for a release of radioactivity inside this structure. Three documented instances of contamination through the common fuel building/turbine building wall were noted.
Site Characterization: Direct measurements were made of each of the interior elevation surfaces as well as the exterior surfaces of the structure. These measurements confirmed the presence of plant-derived radionuclides. Direct measurements on the pool elevation showed a mean gross activity level of 16,900,000 dpm/100 cm 2 and a maximum value of 200,000,000 dpm/100 cm 2. Direct measurements on the +40' elevation showed a mean gross activity level of 5,942 dpm/100 cm 2 and a maximum valueof 19,357 dpm/100 cm 2.
Direct measurements on the building exterior showed a mean gross activity level of 1,408 dpm/100 cm 2 and a maximum value of 21,600 dpm/100 cm 2 . Based on the classification procedure (DSIP-0020) and levels of gross activity reported, the interior of the spent fuel building was determined to be a Class 1, 2 area and the exterior was a Class 2, 3.
HSA Events: HSA Report pg. 63.
Survey Unit Design Information:
The Survey Unit Design Parameters are presented in Table 1 below. The survey unit and measurement locations are depicted on the maps in Attachment 1. Direct measurement locations were determined using a random-start, fixed grid pattern and 245 m2 were scanned for 100% coverage. Samples of removable contamination were collected at each direct measurement location. The instrumentation used for the survey along with the MDC values are listed in Tables 2-1 and 2-2 in Attachment 2.
Page 2 of 11 FSS Summary Report F8121002
Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area: F812 Fuel Storage Building (+)
40' El., Lower Walls Survey Unit: 1002 Structure Surface Class: 1 LTP Table 5-4 SU Area (ml): 245 Evaluator: D. Anderson DCGL (dpm/100 cm2): 43,000 Gross Activity DCGL Area Factor: 3.5 Class I Design DCGLemc 141,900 Class 1 (dpm/100 cm 2):
LBGR (dpm/100 cm 2): 29,107 Adjusted Design Sigma (dpm/100 cm 2): 4,631 Type I Error: 0.05 Type II Error: 0.05 Predominant Nuclide: Cs-137 Sample Area (m2) 7 Class I Scan Area (m2): 245 Scan Coverage (%): 100% Class 1 Zl-, : 1.645 1.645 Sign P: 0.99865 Calculated Relative Shift: 3 Relative Shift Used: 3 Uses 3.0 if Relative Shift is
>3 N-Value: 11 Design N-Value + 20%: 14 NUREG-1575 Table 5-5 Design Min Samples N: 35 Class 1 Grid Spacing L: 2.6 Class 1 Page 3 of I I FSS Summary Report F8121002
Survey Results:
A total of 50 direct measurements were made in F8121002. The results including mean, median, standard deviation and range are shown in Table 2. All direct measurements were less than the DCGL. One of the scan measurements indicated an area of elevated activity. The gamma scan activity ranged from < 877 dpm/100 cm 2 Co-60 and < 1,120 dpm!100 cm2 to 1,128 dpm/100 cm2 Cs-137. Beta scan activity ranged from 1,442 to 243,746 dpm/100 cm 2, based on a surveyor efficiency of 0.5 and no background subtracted. Samples for removable surface activity were all less than 10% of the DCGL as shown in Table 3. Removable surface activity samples were counted for alpha activity and none was detected at the MDC shown in Table 2-1 of Attachment 2.
Page 4 of I11 FSS Summary Report F8121002
Table 2. Direct Measurement Results Measurement ID Gross Activity (dpm/100 .cm F8121002-XOOOIBD 3,494 F8121002-XO002BD 3,197 F8121002-XO003BD 3,307 F8121002-XO004BD 3,296 F8121002-XO005BD 3,726 F8121002-XO006BD 3,516 F8121002-XO007BD 3,241 F8121002-XO008BD 3,461 F8121002-XO009BD 3,417 F8121002-XO010BD 3,891 F8121002-XO011BD 6,680 F8121002-XO012BD 3,957 F8121002-XO013BD 2,436 F8121002-XO014BD 2,480 F8121002-XO015BD 2,877 F8121002-XO016BD 3,428 F8121002-XO017BD 2,877 F8121002-XO018BD 3,274 F8121002-XO019BD 3,186 F8121002-XO020BD 3,571 F8121002-XO021BD 2,998 F8121002-XO022BD 2,701 F8121002-XO023BD 2,513 F8121002-XO024BD 3,560 F8121002-XO025BD 3,020 F8121002-XO026BD 3,263 F8121002-XO027BD 2,690 F8121002-XO028BD 3,252 F8121002-XO029BD 2,623 F8121002-XO030BD .2,513 F8121002-XO031BD 2,513 F8121002-XO032BD 2,590 F8121002-XO033BD 2,381 F8121002-XO034BD 2,690 F8121002-XO035BD 3,208 F8121002-XO036BD 2,943 F8121002-XO037BD 3,329 F8121002-XO038BD 3,373 F8121002-XO039BD 3,274 F8121002-XO040BD 3,505 F8121002-XO041BD 4,078 F8121002-XO042BD 3,770 F8121002-XO043BD 3,593 F8121002-XO044BD 4,828 F8121002-XO045BD 3,428 F8121002-XO046BD 4,123 F8121002-XO047BD 3,704 F8121002-XO048BD 4,123 Page 5 of I I FSS Summary Report F8121002
Measurement ID Gross Activity (dpm(100 cm)"
F8121002-XO049BD 3,803 F8121002-XO050BD 3,450 Mean: 3,343 Median: 3,301 Standard Deviation: 708 Range: 2,381 - 6,680 Page 6 of I I FSS Summary Report F8121002
Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpm/100 cm 2 )
F8121002XO001SM -2.24 F8121002X0002SM -2.24 F8121002X0003SM 0.34 F8121002X0004SM -3.53 F8121002X0005SM 10.68 F8121002X0006SM -3.53 F8121002X0007SM 8.09 F8121002X0008SM -0.95 F8121002X0009SM 0.34 F8121002XO010SM 1.64 F8121002XO011SM 17.13 F8121002X0012SM -3.53 F8121002XO013SM -4.82 F8121002X0014SM -3.53 F8121002X0015SM -0.95 F8121002X0016SM 0.34 F8121002X0017SM 1.64 F8121002X0018SM 5.51 F8121002X0019SM 5.51 F8121002X0020SM 21.01 F8121002X0021SM 0.34 F8121002X0022SM 1.64 F8121002X0023SM 0.34 F8121002X0024SM 10.68 F8121002X0025SM -0.95 F8121002X0026SM -2.24 F8121002X0027SM -4.82 F8121002X0028SM 11.97 F8121002X0029SM 0.34 F8121002X0030SM 0.34 F8121002X0031SM 0.34 F8121002X0032SM 11.97 F8121002X0033SM 6.8 F8121002X0034SM 10.68 F8121002X0035SM 6.8 F8121002XO036SM 2.93 F8121002XO037SM 4.22 F8121002XO038SM 9.38 F8121002XO039SM 10.68 F8121002XO040SM 1.64' F8121002XO041SM 5.51 F8121002XO042SM 4.22 F8121002X0043SM 2.93 F8121002X0044SM 11.97 F8121002X0045SM 18.42 F8121002X0046SM 1.64 F8121002XO047SM 1.64 F8121002XO048SM 24.88 Page 7 of I11 FSS Summary Report F8121002
Measurement ID Surface Beta Activity (dpm/100 cm 2)
F8121002X0049SM 23.59 F8121002X0050SM 2.93 Mean: 4.55 Median: 1.64 Standard Deviation: 7.32 Range: -4.82 to 24.88 Page 8 of I1I FSS Summary Report F8121002
Survey Unit Data Assessment:
The survey design required 50 direct measurements for the Sign Test. The critical value and the results of the Sign Test are presented in Table 4. The sample mean and median values were less than the DCGL. The sample standard deviation was less than the design standard deviation so no additional samples were required.
Page 9 of 11l FSS Summary Report F8121002
Table 4. Data Assessment Results Survey Results Parameter Value Comment Material Background Used (dpm/100 cm 2): N/A Ambient Background Used (dpm/100 cm 2 ): N/A Average Ambient BKG = 0 Actual Direct Measurements (N): 50 Median (dpm/100 cm 2 ): 3,301 Mean (dpm/lO0 cm ):2 3,343 Direct Measurement Standard Deviation 708 (dpm/100 cm 2):
Total Standard Deviation (dpm/100 cm 2): 708 Based on samples and backgrounds.
Maximum (dpm/100 cm 2): 6,680 Material Type: N/A Background Subtract Not Applied Sign Test Final N Value: 50 S+ Value: 50 Critical Value: 31 Sufficient Samples Collected: Yes Maximum Value < DCGL: Yes Median Value < DCGL: Yes Mean Value < DCGL: Yes Maximum Value < DCGLemc: Yes Class 1 Total Standard Deviation <= Sigma: Yes Pass the Sign Test? Yes Reject the Null Hypothesis? Yes Does the-Survey Unit Pass All Criteria? Yes Page 10 of I I FSS Summary Report F8121002
Survey Unit Investigations and Results:
One investigation (scan grid 12) was required for the scan measurements and the results are reported in Attachment 3. The EMC unity rule was not exceeded as shown in Table 3-1.
ALARA Statement:
As stated in Chapter 4 of the LTP, as long as the residual activity within the survey unit is less than the DCGL (i.e. the survey unit average activity is less than the DCGL and the EMC criterion has been met), the ALARA criterion has been met.
Changes in Initial Survey Unit Assumptions:
The survey unit was designed as a Class 1 structure survey and the sample results are consistent with that classification. The variability of the survey results was less than the characterization data used for survey design. One potential area of elevated activity was detected and evaluated as shown in Attachment 3. Therefore the EMC criterion was met.
==
Conclusion:==
The FSS of this survey unit was properly designed as a Class 1 survey based on Table 5-4 of the LTP. The required number of direct measurements was made and the scan coverage met the requirement of Table 5-6 of the LTP. No direct measurements exceeded the DCGL of 43,000 dpm/I00 cm 2 and none of the removable surface activity measurements exceeded 10% of the DCGL. One investigation was required.
The direct measurement data support rejection of the null hypothesis, providing high confidence that the survey unit satisfied the release criteria and that the data quality objectives were met.
It is concluded that survey unit F8121002 meets the release criteria of 10CFR20.1402.
Page 11 of 11 FSS Summary Report F8121002
Attachment 1 Maps October 8, 2008 Survey Unit F8121002
0 W'
0 C')
76.25 ft. - 23.24 mr 0 1 2 3 4 Distance in Meters N
00 C)
C) Location of Fuel Storage Building at Rancho Seco site Map F8121002-1, Fuel Storage Building +40' El.
East Wall (Lower 3 meters) Area Estimate: 83.7 sq. meters
0 76.25 ft. - 23.24 m 00 1 2 3 4 Map F8121002-2, Fuel Storage Building +40' El.
Distance inMeters West Wall (Lower 3 meters) Area Estimate: 83.8 sq. meters
I?
C?
North Wall F-E LO) 40.68 ft. - 12.4 m Column Interior Wall 0 1 2 3 Distance in Meters 4 Map F8121002-3, Fuel Storage Building +40' El.
North Wall (Lower 3 meters) Area Estimate: 34.9 sq. meters Interior Wall and Column Area Estimate: 42.6 sq. meters Page 4 of 20 Att. I Maps F8121002
4+
00 C>~
Ili 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75Il 55 60tJ65l70.k 4550-L 75 80 85 90 95 10 1 95 100 100 110 115 120 125 130 f
135 140 145 150 155 160 165 Map F8121002-4, Fuel Storage Building +40' El.
0 1 2 3 4 Distance in M.eter Lower Walls (Lower 3 meters) Random Start Location
CD Height in meters C0 O P0 2 )
- 1 3J 0 3) 33 3 3 N) 3) 5')2 Map F8121002-5, Fuel Storage Building +40' El.
0 1 2 3 4 ODitance in Meters West Wall Beta Direct Measurements F8121002CO001BD to F8121002C0018BD 2.64 meter grid
Height in i
meters 2.84 m 0.20 m Height in meters 2.84 m 0.20 m Column 3o OE
'0.
0 1 2 3 4 Map F8121002-6, Fuel Storage Building +40' El.
Distance in Meters North Wall Beta Direct Measurements F8121002C0019BD to F8121002C0032BD 2.64 meter grid Page 7 of 20 Att. I Maps F8121002
00Q 0
Height in meters Cj) cE -
E E E E E - E E E E )2 C00 (0 C\J _ __ _ E2O CD U)CO toco.. c 5 EZ 00 N .,*_
C') Map F8121002-7, Fuel Storage Building +40' El.
East Wall Beta Direct Measurements DisaceinMeters F8121002C0033BD to F8121002C0050BD 2.64 meter grid
0r 0
00 Map F8121002-8, Fuel Storage Building +40' El.
West Wall (Lower 3 meters) Gamma Scan Measurements 0 1 2 3 4 F8121002C0001GS to F8121002C0008GS Distance in Meters 12.57 sq. meter field of view Beta Scan Measurements F8121002C0022BS to F8121002C0036BS
Column Map F8121002-9, Fuel Storage Building +40' El.
Ditancei Metr North Wall (Lower 3 meters) Beta Scan Measurements F8121002CO037BS to F8121002C0096BS Page 10 of 20 Att. I Maps F8121002
0
'ft C)
C/)
00 N .
Map F8121002-10, Fuel Storage Building +40' El.
t-j East Wall (Lower 3 meters) Gamma Scan Measurements F8121002C0009GS to F8121002C0016GS 0 1 2 3 Distance in Meters 4
12.57 sq. meter field of view Beta Scan Measurements F8121002C0097BS to F8121002CO111BS
I4 E
A E
T E
It face Column 0 0.5 1.0 1.5 2.0 Distance in Motors Map F8121002-11, Fuel Storage Building +40' El.
Column (Lower 3 meters) Beta Scan Measurements F8121002C0001 BS to F8121002C006BS Page 12 of 20 Att. I Maps F8121002
Map F8121002-12, Fuel Storage Building +40' El.
Column (Lower 3 meters) Beta Scan Measurements
.N 4 F8121002COOO1BS to F8121002CO014BS and
..... Beta Direct Measurement X8121002CO001BD Location of X8121002CO001BD Page 13 of 20 Att. I Maps F8121002
Map F8121002-13, Fuel Storage Building +40' El.
Column (Lower 3 meters) Beta Scan Measurements F8121002CO015BS to F8121002CO021BS Page 14 of 20 Att. 1 Maps F8121002
Map F8121002-14, Fuel Storage Building +40' El.
Lower Wall (10 ft.)
Penetration Beta Scan Measurements F8121002POOOlBS to F8121002POO03BS and F8121002P0008BS to F8121002POO09BS Page 15 of 20 Att. I Maps F8121002
Map F8121002-15, Fuel Storage Building +40' El.
Lower Wall (10Oft) Penetration Beta Scan Measurements F8121002PO004BS to F8121002P0007BS Page 16 of 20 Att. 1 Maps F8121002
Map F8121002-16, Fuel Storage Building +40' El.
Lower Wall (10 ft) Juncture Scan Measurements F8121002CO001JS to F8121002C0004JS and F8121002CO009JS Page 17 of 20 Att. I Maps F8121002
Map F8121002-17, Fuel Storage Building +40' El.
Lower Wall (10 ft) Juncture Scan Measurements F8121002C0005JS to F8121002C0008JS Page 18 of 20 Att, I Maps F8121002
Column Interior Wall 0 1 *2 3 4 Distance in Meters Map F8121002-18, Fuel Storage Building +40'El.
North Wall (Lower 3 meters) Juncture Scan Measurements F8121002COO IOJS to F8121002C0017JS Page 19 of 20 Att. I Maps F8121002
CD 0
t-j C0019JS 00 C) Map F8121002-19, Fuel Storage Building +40' El.
0 1 2 3 D.sIanoe in Meters 4 North Wall (Lower 3 meters) Juncture Scan Measurements F8121002C0018JS to F8121002C0019JS
Attachment 2 Instrumentation October 8, 2008 Survey Unit F8121002
Table 2-1. Survey Unit Instrumentation Instrument Detector MDC Static MDC Scan 2
Model; Serial No. Model; Serial No. (dpm/100 cm ) (dpm/100 cm 2 )
M2350; 180733 43-94B; 148620' 1,550 2,710 M2350; 180733 43-94B; 1486202 2,630 4,580 M2350; 203481 43-68B; H161405 909 2,169 M2350; 203486 43-68B; 161400 909 2,169 M2350; 193715 43-68B; 160703 909 2,169 M2350; 175834 43-68B; 148634 909 2,169 M2350; 193715 43-116-IB; 2560073 1,031 1,552 M2350; 175834 43-116-IB; 1906422 796 3,258 M2350; 175834 43-116-1B; 1906423 1,031 1,552 Tennelec; 0401171
__ __ ______ N/A _____ 11.71 dpm 5.88 dpm c, __ __ N/A 1Metal 2 surfaces Concrete surfaces 3
Concrete surfaces with 1 layer of paint Detector Detector MDC Model No. Serial No.
N/A 1983920 Concrete - 867 d Table 2-2. Investigation Criteria and DCGL Value Parameter (dpm/1 alue d 00 CM) c2 Investigation Criteria - Direct 141,900 Investigation Criteria - Scan 141,900 Investig~ation Criteria - Scan (ISOCS average activity - 12.6 63,000 Cs-137 sq. meter field of view)
DCGLw 43,000 DCGLEMC 141,900
.Page 2 of 2 Att. 2 Instrumentation F8121002
Attachment 3 Investigation October 8, 2008 Survey Unit F8121002
Table 3-1 Survey Unit Investigation Investigation Initial Value Investigation Elevated Area Investigation DCGLenm Level (cpm)Result d Area (mc)Fr DCGLec Result Unity GrLdeInvest o Ia Vs(cpm) (dpm/lOOcm2) Fraction 12 9,100 15,636 15,033 0.012 1,117.7 48,061,981 165,708 0.003 DCGL= SU Mean=
Survey Unit Remainder 43,000 3,343 0.078 EMC Unity Sum 0.081 Page 2 of 2 Att. 3 Investigation F8121002
Attachment 4 Data Assessment October 8, 2008 Survey Unit F8121002
DF8121002 Gross Activity Sample Results Quantile Plot 0 DCGL = 43000 dpm/1 00cm2 8,000 3,000 ~
El * '-:*, * .., . .. '.. . . U.--..... . --:
1-..*,30 tT_
0 20 40 60 80 100
~Percentile SDirect Measurements (dpm/10cm2) - median -- 75th Percentile 50th Percentile
0 F8121002 Gross Activity Sample Results Scatter Plot DCGL = 43000 dpml001cm t 8000 En 7000 0 E 6000
= a am - - - --- - - -
-*- - - - ---------- - - 5467 E5000 CL 0
- a. 4000 0 00 0 0 0 0 0 0 0 3341 C>
Cr)
'a Au 3000 00000 0 00 o 0 2000 i a - a aln anui -s anu -nu a am - ai - -u am -ima m lu -n - a - a- -u oau 121 G 1000 0o 0 02 t*j 0*
Me00u00ment Locaoions L Gross2Activity - Average - - "+3StDev. -,-_"-3StDev
oA- F8121002 Gross Activity Frequency Plot DCGL = 43000 dpm/1 00cm2 17 0
16 15 14 A
-I)
CDQ 13 12 11 U- 10 C. 9 A*
8 crn 0 7 6
5 4
3 2
1 0
a) N-N U')
tQ
[2 Bins - Upper End Value (dpm/1 00cm2) a