ML090930664

Final Status Survey Summary Report for September 5, 2008, Spend Fuel Pool South Wall, (+) 0' El. to (+) 40' El., Survey Unit F8120002

ML090930664
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: ML090830313 ML090830314 ML090830316 ML090830318 ML090830319 ML090830320 ML090830321 ML090830322 ML090830323 ML090830324 ML090830541 ML090830542 ML090830543 ML090830544 ML090830545 ML090830546 ML090830547 ML090830548 ML090830573 ML090850549 ML090850550 ML090850551 ML090850552 ML090850553 ML090850554 ML090850555 ML090850556 ML090850557 ML090850558 ML090850559 ML090850560 ML090850561 ML090850562 ML090890534 ML090890535 ML090890536 ML090890537 ML090890539 ML090890584 ML090890585 ML090890586 ML090890587 ML090890588 ML090890727 ML090900729 ML090900730 ML090900731 ML090900732 ML090900733 ML090900770 ... further results
References
DPG 09-097
Download: ML090930664 (24)

Text

Rancho Seco Final Status Survey Summary Report, September 5, 2008 Spent Fuel Pool South Wall, (+) 0' El. to (+) 40' El.

Survey Unit F8120002 Prepared By: Cý. C/-- Date: 9/6/2-CrJ9g FSS Engineer.

.Reviewed By.: *," D'*

ate: %kh'tos Lead FSS Engineer Approved By: 7 Date:______

Dismantlement Superintendent, Radiological

FINAL STATUS SURVEY

SUMMARY

REPORT Survey Unit:

F8120002, Spent Fuel Pool South 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/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 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 137.68 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 Tables2-1 and 2-2 in Attachment 2.

Page 2 of 8 FSS Summary Report F8120002

Table 1. Survey Unit Design Parameters Survey Design Value Comment Parameter Survey Area: F812 Spent Fuel Pool South Wall Survey Unit: 0002 Structure Surface Class: 1 LTP Table 5-4 SU Area (m2): 137.68 Evaluator: D. Anderson DCGL (dpm/100 cm 2 ): 43,000 Gross Activity DCGL Area Factor: 3.6 Class 1 Design DCGLemc 154,800 Class 1 (dpm/100 cm 2):

LBGR (dpm/100 cm 2): 21,500 Default = 50% DCGL Design Sigma 2 (dpm/100 cm ): 12,246 Type I Error: 0.05 Type II Error: 0.05 Predominant Nuclide: Cs-137 Sample Area (m2): 2.62 Class I 2 137.68 Scan Area (m ):

Scan Coverage (%): 100% Class 1 1.645 Zip: 1.645 Sign P: 0.955435 Calculated Relative Shift:

1:7 1.7 Uses 3.0 if Relative Shift is Relative Shift Used:

>3 N-Value: 14 Design N-Value + 20%: 17 NUREG-1575 Table 5-5 Design Min Samples N: 20 Class I Grid Spacing L: 2.62 Class I Page 3 of 8 FSS Summary Report F8120002

Survey Results:

A total of 20 direct measurements were made in F8120002. 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 < 977 dpm/100 cm 2 Co-60 and < 1,130 dpm/100 cm 2 to 50,475 dpm/100 cm 2 Cs-137. Beta scan activity ranged from 2,399 to 40,311 dpmr/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.

Table 2. Direct Measurement Results Measurement ID Gross Activity (dpm/100 cm F8120002-CO001 BD 7,978 F8120002-CO002BD 2,614 F8120002-CO003BD 3,076 F8120002-CO004BD 3,066 F8120002-CO005BD 1,930 F8120002-CO006BD 1,795 F8120002-CO007BD 1,478 F8120002-COOOBBD 1,463 F8120002-CO009BD 1,650 F8120002-CO01OBD 1,629 F8120002-CO011 BD 1,701 F8120002-CO012BD 1,867 F8120002-CO013BD 2,646 F8120002-CO014BD 2,635 F8120002-CO015BD 3,356 F8120002-CO016BD 1,727 F8120002-CO017BD 3,486 F8120002-CO018BD 2,371 F8120002-CO019BD 1,883 F8120002-CO02OBD 2,381 Mean: 2,537 Median: 2,150 Standard Deviation: 1,430 Range: 1,463 - 7,978 Page 4 of 8 FSS Summary Report F8120002

Table 3. Removable Surface Activity Results Measurement ID Surface Beta Activity (dpm/100 cm 2) i F8120002C0001SM 8.09 F8120002C0002SM 9.38 F8120002C0003SM 5.51 F8120002C0004SM 21.01 F8120002C0005SM 2.93 F8120002C0006SM 0.34 F8120002C0007SM -3.53 F8120002CO008SM . -2.24 F8120002C0009SM 1.64 F8120002C0010SM -2.24 F8120002C001 1 SM -2.24 F8120002C0012SM -0.95 F8120002C0013SM -4.82 F8120002C0014SM -2.24 F8120002C0015SM -2.24 F8120002C0016SM 0.34 F8120002C0017SM 0.34 F8120002C0018SM -0.95 F8120002C0019SM 4.22 F8120002C0020SM -0.95 Mean: 1.57 Median: -0.3 Standard Deviation: 5.93 Range: -4.82 to 21.01 Page 5 of 8 FSS Summary Report F8120002

Survey Unit Data Assessment:

The survey design required 20 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 F8120002

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): 20 Median (dpm/100 cm 2 ): 2,150 2

Mean (dpm/100 cm ): .2,537 Direct Measurement Standard Deviation 1,430 2

(dpm/100 cm ):

Total Standard Deviation (dpm/100 cm 2 ): 1,430 Based on samples and backgrounds.

Maximum (dpm/100 cm 2 ): 7,978 Material Type: N/A Background Subtract Not Applied Sign Test Final N Value: 20 S+ Value: 20 Critical Value: 14 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 F8120002

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 cm2 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 F8120002 meets the release criteria of 10CFR20.1402.

Page 8 of 8 FSS Summary Report F8120002

Attachment 1 Maps September 5, 2008 Survey Unit F8120002

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Map F8120002-1, Fuel Storage Building Location at Rancho Seco site

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CO001Js CO002JS CO003JS Spent Fuel Pool South Wall Map F8120002-8, Spent Fuel Pool South Wall Beta Scan Measurements 0.0 0.5 1,0 1.5 2.0 F8120002C0013BS to F8120002C0030BS and Distance in Meters F8120002C0142BS to F8120002C0147BS Juncture Scan Measurements F8120002C0001JS to F8120002C0007JS Page 9 of 9 Att. 1 Maps F8120002

Attachment 2 Instrumentation September 5, 2008 Survey Unit F8120002

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; 175834 43-116-1B; 190642 491 739 Tennelec; 0401171 N/A 5.88 dpm a,

____ ___ ____ _ __ ___ ____ ___ 11.71 dpm~ N/

MDC Concrete- 1,130 dpm/100 cm2 Cs-137, Concrete - 977 dpm/100 cm2 Co-60 Table 2-2. Investigation Criteria and DCGL Value Parameter (dpm/100 cm 2 )

Investigation Criteria - Direct 154,800 Investigation Criteria- Scan 63,300 Cs-137 (ISOCS average activity - 12.6 20,000 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 F8120002

Attachment 3 Investigation September 5, 2008 Survey Unit F8120002 (none required)

Attachment 4 ,

Data Assessment September 5, 2008 Survey Unit F8120002

F8120002 Gross Activity Sample Results Quantile Plot DCGL = 43000 dpm/1 00cm2 9,000 8,000 CD 7,000 6,000 C)

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I 4-5,000 4,000 3,000 2150 2,000 1,000 0

0 20 40 60 80 100 Percentile

• Direct Measurements (dpm/1O00cm2) -m edian - - - 75th Percentile . 50th Percentile

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F81 20002 Gross Activity Sample Results Scatter Plot DCGL = 43000 dpmi00icm=

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~0 F8120002 Gross Activity Frequency Plot 2

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