ML090930097

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Final Status Survey Summary Report for September 4, 2008, Spent Fuel Pool West Wall, (-) 46 El. to (+) 40 El, Survey Unit F8120001
ML090930097
Person / Time
Site: Rancho Seco
Issue date: 09/05/2008
From: Donna Anderson
Sacramento Municipal Utility District (SMUD)
To:
NRC/FSME
Shared Package
ML090830613 List: ... further results
References
DPG 09-097
Download: ML090930097 (26)
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Rancho Seco Final Status Survey Summary Report September 4, 2008 Spent Fuel Pool West Wall, (-) 4' 6" El. to (+) 40' El.

Survey Unit F8120001 Prepared By:

5. /toO Date:

Iq/,5./,,L FSS Engineer Reviewed By:

iý

(-ý_* kDate:

oI t Lead FSS Engineer Approved By:

7Dismate:mnt 4 -D Dismantlement Su;rintendent, Radiological

FINAL STATUS SURVEY

SUMMARY

REPORT Survey Unit:

F8120001, Spent Fuel Pool West Wall, (-) 4' 6" El. to (+) 40' 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 16,9.00,000 dpm/100 cm2 and a maximum value of 200,000,000 dpm/100 cm2. 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 cm2 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 I 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 185.88 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 9 FSS Summary Report F8120001

Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area:

Survey Unit:

Class:

SU Area (M2 ):

Evaluator:

DCGL (dpm/100 cm'):

Area Factor:

Design DCGLemc (dpm/100 cm 2):

LBGR (dpm/100 cm 2):

Design Sigma (dpm/100 cm 2):

Type I Error:

Type II Error:

Predominant Nuclide:

Sample Area (m2):

Scan Area (m2):

Scan Coverage (%):

ZI-P :

Sign P:

Calculated Relative Shift:

Relative Shift Used:

N-Value:

Design N-Value + 20%:

Design Min Samples N:

Grid Spacing L:

F812

.0001 1

185.88 D. Anderson 43,000 3.5 154,800 21,500 12,246 0.05 0.05 Cs-137 6.88 185.88 100%

1.645 1.645 0.955435 1.7 1.7 14 17 27 2.62 Spent Fuel Pool West Wall Structure Surface LTP Table 5-4 Gross Activity DCGL Class 1 Class 1 Default = 50% DCGL Class I Class 1 Uses 3.0 if Relative Shift is

>3 NUREG-1575 Table 5-5 Class 1 Class 1 I

Page 3 of 9 FSS Summary Report F8120001

Survey Results:

A total of 28 direct measurements were made in F8120001. The results including mean, median, standard deviation and range are shown in Table 2. All direct measurements were less than the DCGL. Five of the ISOCS gamma scan measurements indicated areas of elevated activity. The gamma activity ranged from < 889 dpm/100 cm 2 Co-60 and 848 dpm/100 cm2 to 400,084 dpm/100 cm 2 Cs-137. The scan grids indicating elevated activity were remediated and resurveyed. Residual radioactivity levels following remediation ranged from < 877 dpm/100 cm 2 Co-60 and 848 dpm/100 cm 2 to 52,274 dpm/100 cm2 Cs-137. Beta scan activity ranged from 5,454 to 9,890 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 9 FSS Summary Report F8120001

Table 2. Direct Measurement Results Measurement ID Gross Activity (dpm/100 cm F8120001-CO001BD F8120001-CO002BD F8120001 -CO003BD F8120001 -CO004BD F8120001-CO005BD F8120001-CO006BD F8120001-CO007BD F8120001 -CO008BD F8120001-CO009BD F8120001-Co01 OBD F8120001-Co011BD F8120001-Co012BD F8120001-Co013BD F8120001-CO014BD F8120001-CO015BD F8120001-Co016BD F8120001-Co017BD F8120001-Co018BD F8120001-Co019BD F8120001 -CO02OBD F8120001 -C0021 BD F8120001 -CO022BD F8120001-CO023BD F8120001-CO024BD F8120001-CO025BD F8120001 -CO026BD F8120001 -CO027BD F8120001-CO028BD Mean:

Median:

Standard Deviation:

Range:

1,426 1,644 1,800 2,905 1,878 1,976 5,006 1,758 1,577 1,567 1,587 1,691 2,153 1,660 1,255 1,515 2,303 3,263 5,670 9,819 11,324 18,716 2,065 1,997 2,640 12,921 1,857 2,417 3,800 1,987 4,233 1,255-18,716 Page 5 of 9 FSS Summary Report F8120001

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

F8120001 COOOI SM F8120001 C0002SM F8120001 C0003SM F8120001 C0004SM F8120001 C0005SM F8120001 C0006SM F8120001 C0007SM F8120001 C0008SM F8120001 C0009SM F8120001Co010SM F8120001Co011SM F8120001 C012SM F8120001Co013SM F8120001CO014SM F8120001Co015SM F8120001Co016SM F8120001CO017SM F8120001Co018SM F8120001Co019SM F8120001CO020SM F8120001 C0021 SM F8120001 C0022SM F8120001 C0023SM F8120001 C0024SM F8120001 C0025SM F8120001 C0026SM F8120001 C0027SM F8120001 C0028SM Mean:

Median:

Standard Deviation:

Ranqe:

-6.11 0.34

-0.95 2:93 5.51

-2.24 6.8

-3.53

-3.53 0.34

-3.53 0.34 0.34

-3.53

-4.82

-4.82

-3.53 0.34 18.42 4.22 17.13 11.97 0.34

-0.95 5.51

-4.82 1.64 6.8 1.45 0.34 6.31

-6.11 to 18.42 Page 6 of 9 FSS Summary Report F8120001

Survey Unit Data Assessment:

The survey design required 28 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 7 of 9 FSS Summary Report F8120001

Table 4. Data Assessment Results Survey Results Parameter Value

Comment, Material Background Used (dpm/100 cm 2):

N/A Ambient Background Used (dpm/IO0 cm2):

N/A Average Ambient BKG = 0 Actual Direct Measurements (N):

28 Median (dpm/100 cm 2):

1,987 Mean (dpm/100 cm 2):

3,800 Direct Measurement Standard Deviation 4,233 (dpm/100 cm2):

Total Standard Deviation (dpm/ oo cm-):

4,233 Based on samples and backgrounds.

Maximum (dpm/100 cm 2):

18,716 Material Type:

N/A Background Subtract Not Applied Sign Test Final N Value:

28 S+ Value:

28 Critical Value:

18 Sufficient Samples Collected:

Yes Maximum Value < DCGL:

Yes Median Value < DCGL:

Yes Mean Value < DCGL:

Yes Maximum Value < DCGLemc:

Yes Class I Total Standard Deviation <= Sigma:

Yes Pass the Sign Test?

Yes Reject the Null Hypothesis?

Yes Does the Survey Unit Pass All Criteria?

Yes Page 8 of 9 FSS Summary Report F8120001

Survey Unit Investigations and Results:

Five investigations (scan grids 4, 14, 15, 19 and 20) were 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 I 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. Five potential areas of elevated activity were detected, remediated 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/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 F8120001 meets the release criteria of 10CFR20.1402.

Page 9 of 9 FSS Summary Report F8120001 Maps September 4, 2008 Survey Unit F8120001

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.Attachment 2 Instrumentation September 4, 2008 Survey Unit F8120001

Table 2-1. Survey Unit Instrumentation Instrument Detector MDC Static MDC Scan Model; Serial No.

Model; Serial No.

(dpm/100 cm2 )

(dpm/100 cm 2 )

M2350; 203486 43-68B; 161400 433 1,033 M2350; 175834 43-68B; 190642 491 739 Tennelec; 0401171.

N/A 5.88 dpm a, N/A 11.71 dpm P_

Table 2-2. Investigation Criteria and DCGL Value Parameter (dpm/100 cm 2)

Investigation Criteria - Direct 154,800 Investigation Criteria - Scan (ISOCS average activity - 12.6 63,300 Co-60 sq. meter field of view) 20,000 Co-60 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 F8120001 Investigation September 4, 2008 Survey Unit F8120001

Table 3-1 Survey Unit Investigation ISOCS Area ISOCS ISOCS ISOCS Factor Investigation Initial Value Investigation Elevated for 1 m2 Investigation DCGLemnc Grid Level (dpm/lO0 Result m

DCGLemc Result Unity (dpm/100 cm2 Cs-(cpm)

Area (in2) at edge (dpm/lOOcm2 Fraction of field cm Cs-137) 137) of view Cs-137) 4 63,300 67,189 N/A 12.6 14.6 640,700 47,218 0.0 14 63,300 52,216

-N/A 12.6 14.6 640,700 25,680 0.0 15 63,300 71,954 N/A 12.6 14.6 640,700 14,542 0.0 19 63,300 75,659 N/A 12.6 14.6 640,700 25,133 0.0 20 63,300

.88,506 N/A 12.6 14.6 640,700 16,250 0.0 DCGL SU Mean =

Survey Unit Remainder 43,000 3,800 0.09 EMC Unity Sum 0.09 All of the above grids were initially greater than the ISOCS Investigation Level. Additional ISOCS investigations resulted in the decision to perform additional remediation. The investigation results above represent the residual radioactivity levels after additional remediation.

Page 2 of 2 Att. 3 Investigation F8120001 Data Assessment September 4, 2008 Survey Unit F8120001

(5 0

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F8120001 Gross Activity Sample Results Quantile Plot DCGL = 43000 dpm/100cm2 FM 20,000 18,000 16,000 14,000 12,000 10,000 8,000 6,000 4,000 2,000 0

1987 0

20 40 60 Percentile 80 100 I

+

Direct Measurements (dpn//lOOcrn2)

-medlan

- 75th Percentile -

50th Percentile

('3 00 02 CO O0 0

-k F8120001 Gross Activity Sample Results Scatter Plot DCGL = 43000 dpml00cm=1 25000 20000 E 15000 10000 E

CL 5000

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-5000

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Gross Actity -

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F81 20001 Gross Activity Frequency Plot DCGL = 43000 dpm/1 00cm 2 O0 ci) cia ct-6" U_

U-0 M

o) 21 20 19 18 17 16 15 14 13 12 11 109 765.4321 0

C\\I N-CO n-(0 (0

0 Bins - Upper End Value (dpm/1 00cm2)

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