ML13317A484
| ML13317A484 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 01/19/1983 |
| From: | Baskin K Southern California Edison Co |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TAC-44128, TASK-3.B.2, TASK-TM NUDOCS 8301210249 | |
| Download: ML13317A484 (14) | |
Text
Southern California Edison Company P. 0.
BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 K. P. BASKIN TELEPHONE MANAGER OF NUCLEAR ENGINEERING.
January 19, 1983 (213) 572-1401 SAFETY, AND LICENSING Director, Office of Nuclear Reactor Regulation Attention:
D. M. Crutchfield, Chief Operating Reactors Branch No. 5 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D.C.
20555 Gentlemen:
Subject:
Docket No. 50-206 NUREG-0737, Item III.B.2 - Post-Accident Shielding Post-Implementation Review San Onofre Nuclear Generating Station Unit 1
References:
- 1. Letter, K. P. Baskin, SCE, to D. G. Eisenhut, NRC, Additional Information in Support of Responses to NRC TMI Requirements, January 17, 1980
- 2. Letter, J. G. Haynes, SCE, to D. L. Ziemann, NRC, Implementation of Category A Lessons Learned Requirements, March 25, 1980
- 3. "Nuclear Power Plant Control Room Ventilation System Design for Meeting General Design Criterion 19," presented at the 13th AEC Air Cleaning Conference, K. G. Murphy and Dr. K. M. Campe
- 4. Letter, K. P. Baskin, SCE, to D. M. Crutchfield, NRC, NUREG-0737, Item I.C.1 - Emergency Operating Procedures, December 13, 1982 Reference 1 provided you with the results of our post-accident shielding design review responsive to the requirements of NUREG-0578, Item 2.1.6.b - Design Review of Plant Shielding. This design review described those areas requiring post-accident access and indicated that shielding would be provided to ensure that they were accessible. We also described those areas which, with no shielding additions, wouldbe infrequently accessible and finally, those areas to which access would be restricted.
8301210249 830119 PDR ADOCK& 05000206 P
PDR_
Mr. D. M. Crutchfield
-2 In order to complete the required post-implementation review of the subject requirement, a site visit by representatives of the NRC Revion V staff on November 8 and 9, 1982 was arranged to clarify the information contained in References 1 and 2, and to perform a visual inspection of the shielding modifications at San Onofre Unit 1. As a result of the site visit, additional information was requested in order to complete the post-implementation review.
The purpose of this letter is to provide the additional information requested as a result of the aforementioned site visit. To facilitate your review, we have identified the additional information requested followed by our response.
- 1. Further definition of why those areas described in Item 2 of Activity 4 do not require post-accident access.
Response: o 480 Volt Room -
The equipment powered from the electrical equipment in the 480V room is redundant to that powered from the 4 kV room. This room is infrequently accessible as previously defined in Reference 1.
o MCC No. 3 -
The equipment powered from this distribution panel is not required for accident mitigation.
o Auxiliary Control Panel -
Using a single incident scenario, the control room should not have to be evacuated, and thus use of the auxiliary control panel should not be required.
o AFW Pump Area -
All of the equipment in this area is remotely controlled from the control room.
o SI/FW Pump Area -
All of the equipment in this area is remotely controlled from the control room.
o UPS Battery Area -
The equipment powered from this source is not necessary to meet our safety analysis.
Mr. D. M. Crutchfield
-3
- 2.
A description of the design criteria and assumptions used.
Response
We indicated in Reference 1 that the design review had been performed in accordance with the NUREG-0578 requirements. The criteria used were as follows:
- a. Liquid Containing Systems:
100% of the core equilibrium noble gas inventory, 50% of the core equilibrium halogen inventory, and 1% of the remaining isotopes.
- b. Gas Containing Systems:
100% of the core equilibrium noble gas inventory, 50% of the core equilibrium halogen inventory (except for the control room evaluation for which 25% was used), and 1% of the remaining isotopes.
(Only the containment airborne is considered to be a source and the source is considered to be uniformly spread through the containment free volume.)
- c. The letdown flow is assumed to be isolated; subsequently, use of the waste gas system is terminated, and the residual heat removal system is assumed to be operating for the purposes of the review.
- 3.
Provide the TID Dose Curves for the control room and why is skyshine ignored?
Response
The TID Dose Curves are submitted herewith as Enclosure 1 to this letter and include the skyshine dose. The results demonstrate that the control room dose rate at the Control Operator Console, when averaged over 30 days, as allowed in NUREG-0737, is approximately 8.5 mr/hr.
This value is based upon 100% occupancy for the 30 days.
The dose rate at t=O is approximately 1.0 R/HR and consequently we indicated in Reference 1 that the criteria of GDC 19 are met, but in order to maintain the dose level equal to or less than 15 mr/hr immediately following an accident, additional shielding would be necessary. Our assertion that we meet GDC 19 criteria was based upon the use of the occupancy times in Reference 3. We revised our position in Reference 1 by indicating, in Reference 2, that meeting GDC 19 criteria was adequate and that no further modifications to control room shielding were planned.
The 30 day average dose rate for the northwest corner of the control room area (in back of the vertical boards) is 17.4 mr/hr, based upon 100% continuous occupancy. This area is not shielded by the sphere enclosure building, as is the operator console area, but is very close to the 15 mr/hr criteria., and is considered to be acceptable.
Mr. D. M. Crutchfield
-4 In addition this area is not necessarily occupied on a continuous basis (i.e. 100% of the time) and appropriate warnings will be posted, prior to startup from the current outage, to alert operations staff of the post-accident radiological hazard in this particular area.
- 4. Provide a list of the modifications as defined to the San Onofre Unit 1 Project.
Response
The design criteria were established by the results of the shielding survey. The necessary shielding was identified to the San Onofre Unit 1 Project during a design review meeting on June 26, 1980. The results of this meeting were documented in the meeting minutes dated June 27, 1980. This meeting established the bases, upon which the San Onofre Unit 1 Project performed the civil/structural design of the shielding. A summary of the design information described in the meeting minutes are provided as Enclosure 2 to this letter.
- 5. Provide documentation to establish how the occupancy times were calculated.
Response: The occupancy times that were used to determine the accepability of the present control room shielding were, as stated in our response to item 3 above, taken from the criteria in Reference 3.
- 6. Reference 1 states that as an alternative to shielding modifications inside the Auxiliary Building, letdown flow will be isolated. A visual check of one procedure has verified this to be true, but assurance should be provided to ensure that operators will be made aware of the consequences of letdown flow reinitiation.
Response
We are currently performing a review of the new emergency operating procedures, developed in response to NUREG-0737 requirements, to verify that the applicable procedures require letdown isolation. We will also provide a means to alert operations personnel to consider the radiological effects of reinitiation of letdown flow. As previously identified in Reference 4, these procedures are scheduled to be implemented by August 1, 1983.
- 7. Explain the reduced dose rates in the control room after shielding, as shown on the dose rate maps enclosed with Reference 1, if no new shielding was added to the control room.
Response
The "before" shielding additions dose rate maps are accurate and show the existing dose rates for the control room area and the 480 V room. The reduced dose rates shown for these areas in the "after" shielding additions
Mr. D. M. Crutchfield
-5 dose rate maps were based upon our assumption at the time, that the dose rate would be required to be reduced to < 15 mr/hr immediately following the accident.
Further evaluation of.the integrated dose rate, for the purposes of determining if GDC 19 criteria has been satisfied, has indicated that the TID for the operator console, when the reduced occupancy times of Reference 3 are considered, meets GDC 19 criteria and is < 15 mr/hr, if averaged over 30 days. This was previously stated, in our response to item 3 above. Therefore, additional shielding for these areas was not warranted and we informed you of this fact and explained the situation in Reference 2.
If you require any additional information to complete your post-implementation review of the subject requirement, please let me know.
Very truly yours, Enclosures cc:
R. H. Engelken, Regional Administrator, NRC Region V (3)
M. L. Padovan, NRC Region V (1)
ENCLOSURE 1
ASSUMPTIONS Unit 1 Containment to Unit 1 Control Room
- b.
25% of the core iodine inventory and 100% of the core noble gas inventory c
Containment spray system parameters c1 o -
25 min:
flow is 1080 gpm with 10.0 hr 0.345 hr 4E J-P 25 imn -2 hr flow is 500 gpm with 'E
- 3. hr 0.101 hr
> 2 hr.:
no credit,taken for sprays d Unit 1 Conamet leak rate:
0.12 v/o per day' (0 30 day) axing rate:
0.3229 hr sprayed volume fraction:
0.86 unsprayed volume fraction:
0.14
- e. The source is uniformly distributed inside the containment
- f. X/Q values employed were those for the air intake location 0
8 hr 8.49 (-3) sec/m 8 -
24 hr 6.27 (-3) sec/m3 1 -
4 day 4.40 (-3) sec/m 3 4 -
30 day 2.29 (-3) sec/r 3
ASSUMPTIONS -
continued Uni t -2 containmlfenlt to Unit 1 -Control Room a
Core isotopic source terms as presented in the SONGS 2&3 FSAR veto ad 100% "of the core.nbe a b
25% of the core iodine inventory an inventory become airborne.
- c.
Containment.spray system parameters
.E
.8 with cutoff time 1 hr p
0.22 with cutoff time 38.7 hr
- d.
Unit 2 Containment 0.10 v/o first 2 hrs and 0.05 v/o per day thereafter leak -rate:
1
/
irt4 r
Te source is uniformly distribu td inside the containment f
X/Q values employed were those for the air intake location 3
0- 8hr 8.13 (-4) sec/M 8 -
24 hr 5.30 (-4) sec/m 3 4 day 3.10 (-4) sec/m3 3
4 3 558(-5) sec/
RESULTS unit 1 Containment T
Unf 3 Con trolI Roo ~
7
- a. 0-30 day integrated dose at the Control Operator console:
Direct 4.32 Rem Outside Cloud:
- 0. 27 Re Skyshe 1.56 Rem
,-~Tota 6.15 em, b
0 30' day integrated dose *at-tbe northwest'corner of the cotrlroom area (in back of-vertical -boards):
Direc:
'0. 70 Rem Outside Cloud:
- 0. 2 7,Rem Skyshine:
'5.6-Rem~.
Total 12.53 Rem' Unit 2 Contaiment Unt1CnrlRo 0-30 integrated dose at the Control Operator cnsl Direct:,
0 13 Rem
..Outside Cloud:
0-.10 Rem Total 0.23 Rem The skyshine contribution is negligible;
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ENCLOSURE 2
DESCRIPTION OF THE DESIGN OF THE SAN ONOFRE UNIT 1 SHIELDING Civil/Structural determined the preliminary layout and shielding criteria of shielding structures for the recirculation heat exchanger, the refueling water pump and associated piping, the personnel escape hatch, the dog house, vault, pipe tunnel, and for the large size vent openings of the sphere enclosure building. Nuclear Engineering determined the thickness of the shielding, based upon the shielding design review. The results of which are illustrated in the attached sketches.
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