ML091000372

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Final Status Survey Summary Report for October 8, 2008, Spent Fuel Pool Floor, (-) 4' 6 El. to (+) 0' El., Survey Unit F8120005
ML091000372
Person / Time
Site: Rancho Seco
Issue date: 10/08/2008
From: Donna Anderson
Sacramento Municipal Utility District (SMUD)
To:
NRC/FSME
Shared Package
ML090830613 List: ... further results
References
DPG 09-097
Download: ML091000372 (32)
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Text

r Rancho Seco Final Status Survey Summary Report October 8, 2008 Spent Fuel Pool Floor, (-) 4' 6" El. to (+) 0' El.

Survey Unit F8120005 Prepared By: Aj.' .C__- Date: /lo 96 FSS Engineer Reviewed By: - ;Date: I-- 5I I(T 9 Lead FSS Engineer Approved By: Date: " -O Dismantlement Superintendent, Radiological

FINAL STATUS SURVEY

SUMMARY

REPORT Survey Unit:

F8120005, Spent Fuel Pool Floor, (-) 4' 6" El. to (+) 0' El.

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 cm2 and a maximum value of 200,000,000 dpm/100 cml. Direct measurements on the +40' elevation showed a mean gross activity level of 5,942 dpm/100 cm2 and a maximum value of 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 cm2. 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 175.2 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 8 FSS Summary Report F8120005

Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area: F812 Spent Fuel Pool Floor Survey Unit: 0005 Structure Surface Class: 1

  • LTP Table 5-4 SU Area (m2): 175.2 Evaluator: D. Anderson DCGL (dpm/100 cm 2): 43,000 Gross Activity DCGL Area Factor: 3.6 Class 1 Design DCGLemc 154,800 Class I (dpm/100 cm 2):

LBGR (dpm/100 cm 2): 21,500 Default 50% DCGL Design Sigma (dpm/100 2 cm ): 12,246 Type I Error: 0.05 Type II Error: 0.05 Predominant Nuclide: Cs-137 Sample Area (m2): 6.74 Class 1 2

Scan Area (m ): 175.2 Scan Coverage (%): 100% Class 1 Z-,* : 1.645 ZI-1P :

1.645 Sign P: 0.955435 Calculated Relative Shift: 1.7 Relative Shift Used: 1.7 Uses 3.0 if Relative Shift is

>3 N-Value: 14 Design N-Value + 20%: 17 NUREG-1575 Table 5-5 Design Min Samples N: 26 Class 1 Grid Spacing L: 2.5 Class 1 Page 3 of 8 FSS Summary Report F8120005

Survey Results:

A total of 26 direct measurements were made in F8120005. The results including mean, median, standard deviation and range are shown in Table 2. All direct measurements were less than the DCGL. None of the scan measurements indicated areas of elevated activity. The gamma scan activity ranged from < 1,370 dpm/1 00 cm 2 to 1,863 dpm/100 cm 2 Co-60 and < 1,260 dpm/100 cm2 to 14,901 dpm/100 cm 2 Cs-137. Beta scan activity ranged from 3,357 to 11,100 dpm/100 cm2 , 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.

Table 2. Direct Measurement Results Measurement ID Gross Activit (dpm/100 cm)

F8120005-C00O0 BD 2,044 F8120005-CO002BD 2,314 F8120005-CO003BD 2,111 F8120005-CO004BD 2,324 F8120005-CO005BD 2,438 F8120005-C0006BD 2,153 F8120005-CO007BD 3,916 F8120005-CO008BD 2,018 F8120005-CO009BD 2,122 F8120005-CO01 OBD 2,070 F8120005-Co01o1 BD 2,241 F8120005-CO012BD 4,886 F8120005-CO013BD 2,158 F8120005-CO014BD 2,070 F8120005-CO015BD 2,241 F8120005-Co016BD 19,748 F8120005-C0O017BD 2,293.

F8120005-CO018BD 2,101 F8120005-CO019BD 2,122 F8120005-CO02OBD 2,490 F8120005-C0021 BD 1,738 F8120005-CO022BD 2,184 F8120005-CO023BD 2,148 F8120005-CO024BD 2,210 F8120005-CO025BD 2,578 F8120005-CO026BD 2,002 Mean: 3,028 Median: 2,171 Standard Deviation: 3,470 Range: 1,738- 19,748 Page 4of 8 FSS Summary Report F8120005

Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpm/100 cm 2 )

F8120005C0001 SM -0.95 F8120005C0002SM 8.09 F8120005C0003SM -3.53 F8120005C0004SM 0.34 F8120005C0005SM -0.95 F8120005C0006SM 0.34 F8120005C0007SM -2.24 F8120005CO008SM -2.24 F8120005C0009SM -3.53 F8120005C0010SM -2.24 F8120005C001 I SM -0.95 F8120005C0012SM 4.22 F8120005C0013SM -4.82 F8120005C0014SM -3.53 F8120005C0015SM 0.34 F8120005C0016SM -0.95 F8120005CO017SM -4.82 F8120005CO018SM -2.24 F8120005C0019SM 0.34 F8120005C0020SM -0.95 F8120005C0021 SM -2.24 F8120005C0022SM -2.24 F8120005C0023SM -2.24 F8120005C0024SM -3.53 F8120005C0025SM -2.24 F8120005C0026SM * -0.95 Mean: -1.29 Median: * -2.24 Standard Deviation: 2.7 Range: -4.82 to 8.09 Page 5 of 8 FSS Summary Report F81-20005

Survey Unit Data Assessment:

The survey design required 26 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 6 of 8 FSS Summary Report F8120005

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): 26 Median (dpm/100 cm 2): 2,171 Mean (dpm/100 cm 2): 3,028 Direct Measurement Standard Deviation 3,470 2

(dpm/100 cm ):

Total Standard Deviation (dpm/100 cm 2): 3,470 Based on samples and backgrounds.

Maximum (dpm/100 cm2): 19,748

. Material Type: N/A Background Subtract Not Applied 26 Sign Test Final N Value:

S+ Value: 26 Critical Value: 17 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 7 of 8 FSS Summary Report F8120005

Survey Unit Investigations and Results:

No investigations were required for either direct or scan measurements and no investigation results are reported.

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. No potential areas of elevated activity were detected. 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/100 cm 2 and none of the removable surface activity measurements exceeded 10% of the DCGL. No investigations were 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 F8120005 meets the release criteria of 10CFR20.1402.

Page 8 of 8 FSS Summary Report F8120005

Attachment 1 Maps October 8, 2008 Survey Unit F8120005

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Location of Fuel Storage Building inside the Industrial Area 00 (DI I Map F81 20005-1, Spent Fuel Pool Floor & Cask Pit Location of Fuel Storage Building at Rancho Seco site

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N 0.0 0.5 1.0 1.5 2.0 Map F8120005-2, Spent Fuel Pool Floor Distance in Moters Area Estimate: 160.37 sq. meters Note: Wall Area in gray not included in area estimate.

Page 3 of 17 Att. I Maps F8120005

Cask Pit Wall Elevation Facing North

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-- -- - -- --- - -E- - -411.67 3.81 m Cask Pit Wall Elevation Facing East El. c0'0

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3.2 m Cask Pit Wall Elevation Facing South F=L.-0 0' k E El. -4' 6" 3.81 m 0.0 0.5 1,0 1.5 2.0 Distance in Meters Map F8120005-3, Spent Fuel Pool Floor Area Estimate: 14.84 sq. meters Note: Cask Pit West Wall included in Final Survey Package F8120001.

Page 4 of 17 Att. 1 Maps F8120005

Page 5 of 17 Att. I Maps F8120005 Distance from North Wall in meters

- 1.511 m 4.10 m 6.69 m 9.28 m 11.87 m N

14.46 m EE 0 2.43 m 5.02 m 7.61 m 10.20 o E Map F81ZUUU5-5, Spent F-uel Pool Floor Beta Direct Measurements 0.0 0.5 1,0 1.5 Distance in Moters 2.0 F8120005C0001BD to F8120005C0021BD 2.59 sq. meter arid spacino Page 6 of 17 Att. I Maps F8120005

Cask Pit Wall Elevation Facing North T

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2.43 m from West Pit Wall N

Map F8120005-6, Spent Fuel Pool Floor Beta Direct Measurements 0 .0 fM 0.5 1.0 1.5 2.0 F8120005C0022BD to F8120005C0026BD Distance in Meters 2.59 sq. meter grid spacing Page 7 of 1.7 Att. 1 Maps F8120005

T 0E 12.55 m 15.26 m 17.97 m S(

Map F8120005-7, Spent Fuel Pool Floor ISOCS Gamma Scan Measurements F8120005C0001GS to F8120005C0009GS 0.0 0.5 1.0 1.5 2.0 12.57 sq. meter field of view Dislance in Meters F8120005CO01OGS to F8120005C0015GS 7.07 sq. meter field of view Page 8 of 17 Att. I Maps F8120005

N 6c C Map F8120005-8, Spent Fuel Pool Floor ISOCS Gamma Scan Measurements 0.0 0.5 1.0 1.5 2.0 Distance in Meters F8120005C0016GS to F8120005C0041GS 1 m and 1.5 m concrete dpm Page 9 of 17 Att. I Maps F8120005

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T L* 1/.4*, HI I II Map F8120005-9, Spent Fuel Pool Floor All ISOCS Gamma Scan Measurements Page 10 of 17 Att. I Maps F8120005

C*kPi all Elevation Fa North N orth Pit .. . \-all 0.67 m dow !C 05 G ---- ---- Co - - - -

North PitWa-C 0.642mfrom

- 0.64 m North Pitfrom Wall ----

0.671 mddown SouthPit CO42GS------- hll 2.59 m from CO4---------------G C//

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[ E6North O Pit Walld 0.67 m from 1.90 m from 3.14 m from West Pit Wall West Pit Wall West Pit Wall Map F8120005-10, Spent Fuel Pool Floor ISOCS Gamma Scan Measurements 0.0 0.5 1,o 1.5 2.0 F8120005C0042GS to F8120005C0050GS Distance in Meters 3 sq. meter field of view Page 11 of 17 Att. I Maps F8120005

Distance 10.38 m 1.42 m 2.45 m 3.49 m - in meters from North Wall

- 0.75 m i11 ~ZIZ~ 2.39 m II III-

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Map F8120005-11, Spent Fuel Pool Floor ISOCS Gamma Scan Measurements F8120005C0051GS to F8120005C0067GS 3 sq. meter field of view F8120005C0068GS 1.5 meter concrete dpm Page 12 of 17 Att. I Maps F8120005

N 0.0 0.5 1.0 1.5 2.0 Map F8120005-12, Spent Fuel Pool Floor Distance in Meters Juncture Scan Measurements F8120005CO001JS to F8120005C0003JS Page 13 of 17 Att. 1 Maps F8120005

Cask Pit Wall Elevation Facing North El- 0' 0" El. -4'6"

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Cask Pit Wall Elevation Facing South

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Map F8120005-13, Spent Fuel Pool Floor Juncture Scan Measurements F8120005C0004JS and F8120005C0006JS Page 14 of 17 Att. 1 Maps F8120005

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Spent Fuel Pool floor Photos-1 Page 15 of 17 Att. 1 Maps F8120005

Spent Fuel Pool floor Photos-2 Page 16 of 17 Att. 1 Maps F8120005

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Attachment 2 Instrumentation October 8, 2008 Survey Unit F8120005

Table 2-1. Survey Unit Instrumentation Instrument Detector MDC Static MDC Scan Model; Serial No. Model; Serial No. (dpm/100 cm 2 ) (dpm/100 cm 2 )

M2350; 175834 43-68B; 148634 433 1,033 M2350; 175834 43-116-1B; 190642 491 739 5.88 dpm a,N/

Tennelec; 0401171 N/A dpm N/.8 NA

_____ _____ 11.71 dpmf3 _ _ _ _ _ _ _

Instrument I Detector Detector MDC Model No. Serial No.

Concrete - 1,240 dpm/100 cm 2 Cs-137, ISOCS N/A 1983920 Concrete - 783 dpm/100 cm 2 Co-60 Concrete - 1,260 dpm/100 cm 22 Cs-137, ISOCS N/A 2983947 Concrete- 1,370 dpm/100 cm Co-60 Table 2-2. Investigation Criteria and DCGL Value Parameter (dpm/100 cm 2 )

Investigation Criteria - Direct 154,800 Investigation Criteria - Scan 154,800 Investigation Criteria- Scan 63,300 Cs-137 (ISOCS average activity - 12.6 20,000 Co-60 sq. meter field of view)

Investigation Criteria - Scan 115,000 Cs137 (ISOCS average activity - 7.0 40,000 Co60 sq. meter field of view)

Investigation Criteria- Scan 180,000 Cs-137 (ISOCS average activity - 3.1 60,000 Co-60 sq. meter field of view)

DCGLw 43,000 DCGLEMC 154,800 Page 2 of 2 Att. 2 Instrumentation F8120005

Attachment 3 Investigation October 8, 2008 Survey Unit F8120005 (none required)

Attachment 4 Data Assessment October 8, 2008 Survey Unit F8120005

CF8120005 Gross Activity Sample Results Quantile Plot o DCGL = 43000 dpm/1 00cm2 25,000 -

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