ML090930098

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Final Status Survey Summary Report for September 5, 2008, Spent Fuel Pool East Wall, (+) 0 El. to (+) 40 El., Survey Unit F8120003
ML090930098
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: ML090930098 (26)
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Rancho Seco Final Status Survey Summary Report September 5, 2008 Spent Fdel Pool East Wall, (+) 0' El. to (+) 40' El.

Survey Unit F8120003 Prepared By:

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Date:./.b/c.3 FSS Engineer Reviewed By:

Date:

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Lead FSS Engineer Approved By:_

_________Date:_________

Dismantlement Superintendent, Radiological

FINAL STATUS SURVEY

SUMMARY

REPORT Survey Unit:

F8120003, Spent Fuel Pool East Wall, (+) 0' 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 16,900,000 dpm/1 00 cm2 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 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 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 206.63 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 F8120003

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

Survey Unit:

Class:

SU Area (m2):

Evaluator:

DCGL (dpm/ 100 cm 2):

Area Factor:

Design DCGLemc (dpm/100 cM2):

LBGR (dpm/100 cm2):

Design Sigma (dpm/100 cM2 ):

Type I Error:

Type II Error:

Predominant Nuclide:

Sample Area (m2):

Scan Area (Mn2):

Scan Coverage (%):

Zl-( :

Sign P:

Calculated Relative Shift:

Relative Shift Used:

N-Value:

Design N-Value + 20%:

Design Min Samples N:

Grid Spacine L:

F812 0003 1

206.63.

D. Anderson 43,000 3.6 154,800 21,500 12,246 0.05 0.05 Cs-137 6.89 206.63 100%

1.645 1.645 0.955435 1.7 1.7 14 17 30 2.62 Spent Fuel Pool East Wall Structure Surface LTP Table 5-4 Gross Activity DCGL Class 1 Class 1 Default = 50% DCGL Class 1 Class 1 Uses 3.0 if Relative Shift is

>3 NUREG-1575 Table 5-5 Class I Class 1 Page 3 of 8 FSS Summary Report F8120003

Survey Results:

A total of 30 direct measurements were made in F8120003. 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 activity ranged from < 869 dpm/100 cm 2 to 1,000 dpm/100 cm 2 Co-22 60 and 558 dpm/100 cm to 70,177 dpm!100 cm 2 Cs-137. Beta scan activity ranged from 4,871 to 6,404 dpm/l100 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.

Table 2. Direct Measurement Results Measurement ID Gross Activity (dpm/100 cm F8120003-COOOIBD F8120003-CO002BD F8120003-CO003BD F8120003-C0004BD F8120003-CO005BD.

F8120003-CO006BD F8120003-CO007BD F8120003-CO008BD F8120003-CO009BD F8120003-CO01 OBD F8120003-COOlI BD F8120003-CO01 2BD F8120003-CO013BD F8120003-CO014BD F8120003-COOl 5BD F8120003-Co016BD F8120003-Co017BD F8120003-CO01 8BD F8120003-Co019BD F8120003-C0O02OBD F8120003-C0021 BD F8120003-CO022BD F8120003-C0023BD F8120003-CO024BD F8120003-C0025BD F8120003-C0026BD F8120003-CO027BD F8120003-CO028BD F8120003-C0029BD F8120003-C0030BD Mean:

Median:

Standard Deviation:

Range:

3,320 2,184 3,346 2,620 2,355 1,650 1,867 2,065 1,738 1,935 2,236 1,857 1,561 1,899 1,852 1,707 1,691 1,753 13,466 5,198 2,983 5,670 3,242 3,512 1,888 2,215 1,987 1,878 2,402 1,867 2,798 2,026 2,243 1,561 - 13,466 Page 4 of 8 FSS Summary Report F8120003

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

F8120003C0001SM F8120003C0002SM F8120003C0003SM F8120003C0004SM F8120003C0005SM F8120003C0006SM F8120003C0007SM F8120003C0008SM F8120003C0009SM F8120003C0010SM F8120003C0011SM F8120003C0012SM F8120003C0013SM F8120003C0014SM F8120003C0015SM F8120003C0016SM F8120003C0017SM F8120003C0018SM F8120003C0019SM F8120003C0020SM F8120003C0021SM F8120003C0022SM F8120003C0023SM F8120003C0024SM F8120003C0025SM F8120003C0026SM F8120003C0027SM F8120003C0028SM F8120003C0029SM F8120003C0030SM Mean:

Median:

Standard Deviation:

Rancie:

-0.95 2.93 4.22

-0.95 4.22

-0.95 4.22

-3.53 11.97 1.64

-2.24 1.64

-2.24

-0.95 0.34 1.64

-0.95 0.34 1.64 2.93 2.93

-0.95 4.22

-0.95 2.93 0.34

-2.24

-4.82

-0.95 10.68 1.21 0.34 3.66

-4.82 to 11.97 Page 5 of 8 FSS Summary Report F8120003

Survey Unit Data Assessment:

The survey design required 30 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 F8120003

Table 4. Data Assessment Results Survey Results Parameter Value Comment Material Background Used (dpm/100 cm2):

N/A Ambient Background Used (dpm/100 cm 2):

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

30 Median (dpin/100 cm 2):

2,026 Mean (dpm/100 cm 2):

2,798 Direct Measurement Standard Deviation 2,243 (dpm/100 cm 2):

Total Standard Deviation (dpm/100 cr 2):

2,243 Based on samples and backgrounds.

Maximum (dpm/100cm 2):

13,466 Material Type:

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

30 S+ Value:

30 Critical Value:

20 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 F8120003

Survey Unit Investigations and Results:

No investigations were required for either direct or scan measurements and no investigation results are reported. (Note: the high scan value of 70,177 dpm/100 cm2 Cs-137 is the result of a 3.1 sq. meter ISOCS measurement with a correlating investigation level of 180,000 dpm/100cm 2 Cs-137: no scan values exceeded their corresponding investigation levels as shown in Table 2-2).

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 I 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 F8120003 meets the release criteria of 1 OCFR20.1402.

Page 8 of 8 FSS Summary Report F8120003 Maps September 5, 2008 Survey Unit F8120003

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

Model; Serial No.

(dpm/100 cm2 )

(dpm/100 cm2 )

M2350; 203486 43-68B; 161400 433 1,033 M2350; 142509 43-68B; 160696 433 1,033 Tennelec; 0401171 N/A 5.88 dpm a, N/A 11.71 dpm P_

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

Investigation Criteria - Direct 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 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 F8120003 Investigation September 5, 2008 Survey Unit F8120003 (none required)

Data Assessment September 5, 20,08 Survey Unit F8120003 r"

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