ML20005B645
| ML20005B645 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 06/30/1981 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Stolz J Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.B.2, TASK-TM TAC-47971, NUDOCS 8107080476 | |
| Download: ML20005B645 (9) | |
Text
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. f 'y EJSMUD SACRAMENTO MUNICIPAL UTILITY DISTRICT C 62o1 S Street. Box 15830. Sacramento, Cahfornia 95813; (916) 452 3211
/h June 30, 1981
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'S; v.s. g g y ;p N'^N),6 DIRECTOR OF NUCLEAR REACTOR REGULATION A
V ATTENTION JOHN F STOLZ, CHIEF OPERATING REACTOR BRANCH N0 4
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U S NUCLEAR REGULATORY COMMISSION WASHINGTON D C 20555 DOCKET 50-312 RANCHO SECO NUCLEAR GENERATING STATION UNIT N0 1 NUREG 0737 ITEM II.B.2, PLANT SHIELDING REVIEW The Sacramento Municipal Utility District has reviewed your letter of June 11,1981.
As requested by your letter, the District provides the requested information in the attachment to this letter.
If we can provide any additional information or justification on these items, please advise.
a5 h14Mg John. Mattimoe Assistant General Manager and Chief Engineer Enclosures f.(PDRADOCK I(0
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4 SACRAMENTO MUNICIPAL UTILITY DISTRICT POST ACCIDENT SHIELDING REVIEW On January 16, 1980, the District provided to you in response to item 2.1.6.b.
of NUREG 0578, a description of the assumptions used to perform dose rate calculations en fluid systems potentially. containing high source level fluids.
On April 11, 1980, the District prcvided upon your request: radiation zone maps of the plant, derived from a shielding study; a description of the reactor coolant drain tank and waste gas system contributions to the dose rate; a listing of safety related equipment affected by the. dose rates; a description of our ongoing effort to evaluate auxiliary building access' requirements; and a description o' our proposed shielding modifications.
The following description provides the necessary information to augment the previously submitted information.
1.
Summary Description of Final Building Design Review.
Auxiliary building and vital area dose rates were evaluated to determine the contributions of reactor building penetrations and the post accident sampling system. Also the letdown system was removed from the shielding review since it is no longer required.
From the finalized results of this review, Auxiliary Building access requirements are being evaluated to determine the need for localized shielding.
2.
Results of Shielding Design Review The results of the t.ontribution from the reactor building penetrations indicates that accessibility and habitability of certain vital post accident areas are significantly limited. As a result of this problem, modifications will-be n'ade.
The modifications are described in paragraph 3 of this a ttachment, a.
Reactor Building Penetrations (1) Personnel Access Hatch.
The personnel access hatch is a cylindrical type of arrangement.
.The two :: teel doors and the steel penetration provide very little shielding of the reactor building atmosphere source term. 3The dose rate from the penetration's shine is approximately 10 times that of the reactor building contact dose rate.
(2) Reactor Building Purge Penetrations.
The two 66 inch diameter purge penetrations consist of two steel penetrations and two five inch thick steel butterfly valves per penetration.
This configuration also provides limited shielding from the reactor building atmosphere source term. The3 radiation shine from these penetrations is also approximately 10 times that of the reactor. building contact dose rate.
Post Accident Shielding Review (3) Personnel Emergency Escape Hatch.
The personnel emergency escape hatch is a cylindrical airlock type of an arrangement. Just as with the personnel access hatch, the steel lock and associated doors and bulkheads provide limited shielding from the reactor building atmosphere source term. Tge radiagionshinefromthispenetrationisalsoapproximately10 to 10 times that of the reactor building contact dose rate.
(4) Main Steam Line Penetrations.
The main steam line penetrations are typical mechanical penetrations with 36 inch steam lines penetrating them. The associated piping and penetration steel provides limited shielding from the reactor building atmospheric source term.3 The dose rate from these pene-trations is also approximately 10 times that of the reactor building contact dose rate.
(5) Electrical Penetrations.
There are currently 35 electrical penetrations which contribute a substantial reactor building atmospheric source term shine into the auxiliary building. The contribution from these electrical penetrations can be divided into two areas, i.e., the two electrical penetration. rooms. The contribution from each of these areas is approximately a factor of ten higher than the reactor building contact dose rate.
{6) Equipment Hatch..
The equipment hatch is a large cylindrical equipment access port with a steel. hemispherical cover. Additionally, there are two large concrete missile barrier shield doors on the exterior of the reactor building. The combination of this door and the equipment hatch cover.provides a minimum amount of shielding from the reactor building atmosphere source term.
The contribution from the equipment 4
hatch is a factor of approximately 10 greater than the contact dose of the reactor building, b.
The Post Accident Sampling System.
The post accident sampling system will contribute only to auxiliary building dose rates when in use since the system is designed to be flushed after each use. The post accident sampling system piping was routed through a high post accident radiation zone to limit the amount of additional radiation exposure; however, in order to route the piping to an acceptable location for compliance with the sampling access require-ments, we were unable to always stay in a high radiation zone. Therefore, there are certain areas of the sampling system piping that will need shielding.
Post Accident Shielding Review 1 3.
Description of Modification a.
Reactor Building Penetrations All reactor building penetrations that provide a substantial con-tribution to auxiliary building and vital area dose rates will be shielded to the equivalent to the contact dose rate of the reactor building.
(1) Personnel Access Hatch (Figure 1)
The personnel access hatch will be shielded utilizing water as a shield media. A redundant Class 1 water fill system will be provided to flood the reactor building personnel access hatch in the event of a Reg Guide 1.4 source term type accident.
Filling operation will be done remotely using Class 1 water systems, using Class 1 valving and piping. This system will be tested. in a manner similar to the reactor building sprays. Water will be shown to be available and that the valves operate. There is no intention to fill the personnel access hatch, except under conditions equivalent to Reg Guide 1.4.
(2): Reactor Building Purge Penetrations (Figure 2)
The reactor building purge penetrations will be shielded utilizing water as the shield media. The water will not be pumped directly into the reactor building purge penetrations; however, collapsible rubber bags will be used to hold the water. This allows for shielding in the event of a single failure of a containment isolation valve. The rubber bags will be constructed to the same interior diameter as the reactor building purge penetrations and will be filled using a Class 1 redundant water supply. The reactor building purge penetrations shielding system will be tested periodically for functional verification of bag integrity and operability.
(3) Personnel Emergency Escape Hatch (Figure 3)
The personnel emergency escape hatch will be shielded by upgrading
' the existing " Doghouse" or enclosure structure around the escape hatch, providing both shielding and labyrinth scattering to limit vital area dose rates.
(4) Steam Line Penetrations (Figure 4)
The steam line penetrations will be shielded utilizing a concrete wall as a shield material.
Class 1 concrete walls will be con-structed to limit the direct shine of radiation into vital areas.
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Post Accident' Shielding Review (5) Elcctrical Penetrations The electrical penetrations will be shielded using lead or lead equivalent shield material. This item is still under evaluation, with respect to the exact design of the shielding modifications; however, our conceptual. idea is to use synthetic silicone shield material, such as a lead impregnated silicone.
.(6) The Eqsipment Hatch Due to the size of the equipment hatch, considerations are still being given to methods of shielding. We are considering the possibility of utilizing administrative controls to limit 4
personnel exposure from the equipment hatch; however, this may not be possible. We are also presently evaluating the use of a movable tank that could be filled with water in the ever.t of
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Reg Guide 1.4 source term.
b.
Post Accident Sampling System Portions of the post accident sampling system that provide additional dose rates to the auxiliary building area doses will be' shielded utilizing lead lagging on the piping.
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