ML19319B892

Forwards Evaluation of Consequences of Postulated Fuel Handling Accident Inside Containment

ML19319B892
Person / Time
Site:	Davis Besse
Issue date:	05/06/1977
From:	Roe L TOLEDO EDISON CO.
To:	Stolz J Office of Nuclear Reactor Regulation
References
NUDOCS 8001290617
Download: ML19319B892 (6)

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cATE OF CCCUMENT Toledo Edison Company 5/6/77 i

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DESCRIPTsoN ENCLoSU R E Ltr. trans the following:

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Mr. John F. Stolz, Chief MAY111977* r Light Water Reactors Branch I k u p moup55 Division of Project Management V

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Dear Mr. Stolz:

As requested in your letter dated March 10, 1977 concerning the analysis of a postulated Fuel Handling Accident inside containment for Davis-Besse Unit 1, we are enclosing, as Attachment 1, a detailed evaluation of the potential consequences of such an accident. Our evaluation indicates that site boundary doses are well within the guidelines of 10 CFR Part 100, even assuming no isolation of containment nor filtration of the activity postulated to be released.

This information will be presented in Section 15.4.7.3 in Revision 27 of the FSAR as shown on Attachment 2.

Yours very truly, f

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' - Fuel Handling Accident Inside Davis-Besse Unit 1 Containment - Davis-Besse Nuclear Power Station Unit 1 FSAR Section 15.4.7.3 db e/10

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THE TCLECO EDISCN COMPANY EDISCN PLAZA 300 MACISON AVENUE TCLEDJ. CHIO 43652

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ATTACHMENT 1 Fuel Handling Accident Inside Davis-Besse Unit 1 Containment 1

In response to your letter dated March ' 3,1977, on the subject of the fuel j

handling accident inside the containment for Davis-Besse Unit 1, we have evaluated the potential site boundary radiation exposure and have found it to be well within the exposure guidelines of 10 CFR Part 100, even assuming no isolation of the containment nor filtration of the activity postulated to be released.

1 The site boundary thyroid and whole body doses have been found to be 44.7 Rem.and 0.17 Rem respectively.

Th' following assumptions were utilized in the analysis:

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1. Power level is 2772 MWT j

2. The accident occurs at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> following reactor shutdown l

3. Noble gas and iodine gap activities as' based on Regulatory Guide 1.25 i

4. One entire assembly is considered damagei

5. A time averaged radial peaking factor on an assembly basis of 1.4 is utilized

6. The gap activity in the damaged fuel assembly is assumed to be released i

to the pool. All the noble gas activities that are released to the pool

, are assumed to escape from the pool; one percent of the iodine activities that as released to the pool are assumed to esecpe from the pool.

7. Containment isolation is not assumed.

8. An instantaneous release.(very hinh escape rate) from the containment is assumed to ensure that all the ivity comin7 out of the pool is released to the environment in a short ti_r.

9. Atmospheric dispersion factor (X/Q) at site boundary is 1.9 x 10-0 sec3 m

10. No filtration is assumed i

Containment purge exhaust radiation detectot s RE~iOS2A, B, and C, shown on FSAR Figure 9-12A and described in FSAR table 11-i0, will alarm and shutdown the purge system as described on FSAR page 6-38.

This instrumentation is non-safety grade and was not considered in the analysis.

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In addition to the above, safety grade containment radtation monitors RE-2004, 2005, 2006, and 2007, a part of the safety features actuation system, will

. isolate the containment purge system isolation valves CV5005, 5006, 5007 and 5008 upon sensing high radiation in the contain=ent (See FSAR tabl. 7-5, SFAS Actuation Surmary). The technical specifications (Table 3.3-3, SFAS Instrumen-tation) require this instrumentation to be operable during all codes, including refueling. Operating requirements of the instrumentation is provided in FSAR table 1

7-6.

The containment purge inlet and exhaust isolation valves are designed

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ATTACIIMENT 1 (Cont'd)

Fuel Handling Accident Inside Davis-Sesse Unit 1 Containment and tested to close in 10 seconds as noted in FSAR table 6-8 and technical specification table 3.6-2, Containmeae Isolation Valves. Technical speci-fication table 3.3-5, SFAS Response Times, requires a system response for i

valve closure in 15 seconds.

Since the fuel handling accident evaluation conservatively took no credit for the above isolation functions, no assessment of transit times or relative location of radiation monitors with respect to release points is required.

Charcoal filtration is available by manual alignment to the safety grade emergency filtration system, as noted on FSAR page 6-38.

For conservatism, no filtration credit was assumed in the analysis.

It is concluded, therefore, that Davis-Besse Unit I has been designed to minimize the consequences of a fuel handling accident inside the containment.

This conclusion is supported by the above conservative evaluation.

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e D-B 15.4. 7. 3 Accident Analvsis - Accident Inside Containment 15.4.7.3.1 Safety Evaluation Criterion The safety evaluation criterion for this accident is that resultant doses shall not exceed 10 CF2 Part ICO guideline values.

1 15.4.7.3.2 Analysis The following assumptions were used in the analysis:

(1)

The accident occurs at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> following reactor shutdown.

(2)

Noble gas and iodine gap activities are based on Regulatory Guide 1.25.

(3)

Ore entire asse=bly is considered damaged.

(4)

A time-averaged radial peaking factor on an assembly basis of 1.4 is utilized.

(5)

The gap activity in the damaged fuel assembly is assu=ed to be released to the pool.

All the noble gas activitias that are released to the pool are assu=ed to escape from the pcol; one l

percent of the iodine activitics that are released to the pool are assumed to escape from the ycol.

27 (6)

Containment isolation is not assu=ed.

(7)

On instantaneous release (very high escape rate) fres the centain-l ment is assumed to ensure that all the activity coming out of the a

pool is released to the environ =ent in a short time (see Table l

15.4.7-5).

l (8)

Atmospheric dispersion factor (X/Q) at site bcundary is 1.9x10~4jec a i and at LPZ it is 9.9x10 see.

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m (9)

No filtration is assu=ed.

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15.4.7.3.3 Environ = ental Consequences j

The activity is assumed to be released over 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. At=ospheric dilution for site boundary and LP: is calculated using the 2-hour atmospheric dispersicn I

coefficient develcped in Section 2.3.

Table 15.4.7-4 gives the calculatad doses. These results are well within the 10 CFR Part 100 guideline values.

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1 Revisica 27 2

15-121b (2)

Page 1 j7

D-B Table 15.4.7-4 Resultan't Loses From Fuel-Handline Accident InsiheCentainment Exclusion LPZ Area Boundary Boundarv Thyroid dose (rem) 44.7 2.33 -3 Wole body dose (rem) 0.7 8.86 x 10 Table 15.4.7-5 Activity Released to the Atmosphere Due to the Postulated Fuel-Handling Accident Inside Contain=ent (C1) n I-131 4.26 x 10' I-132 3.11 x 10 27 2

I-133 1.18 x 10

-22 I-134 1.47 x 10

-l I-135 6.86 x 10 o

Xe-131m 3.50 x 10' Xe-133n 1.28 x 10 Xe-133 8.55 x 10 Xe-133m 0

Xe-135 5.07 x 10-Xe-137 0

-0 Xe-133 5.67 x 10 Kr-82m 2.43 x 10-

-1 Kr-85c 2.93 x 10 Kr-35 2.48 x 10

-3 Kr-87 3.70 x 10 Kr-88 1.23 x 10' Kr-89 0

Revision 27 15-121b (3) ei Page 2