ML20035C676
| ML20035C676 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 04/01/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20035C675 | List: |
| References | |
| NUDOCS 9304080290 | |
| Download: ML20035C676 (6) | |
Text
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UNITED STATES y.
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.1 NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20%D001 k,,. #'
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 80 TO FACILITY OPERATING LICENSE NO. DPR-80 AND AMENDMENT NO. 79 TO FACILITY OPERATING LICENSE N0. DPR-82 PACIFIC GAS AND ELECTRIC COMPANY DIABLO CANYON NUCLEAR POWER PLANT. UNITS 1 AND 2 DOCKET NOS. 50-275 AND 50-323
1.0 INTRODUCTION
By letter of November 15, 1990, as supplemented June 20, 1991, October 8, 1991 and June 5,1992, Pacific Gas and Electric Company (or the licensee) submitted a request for changes to the Technical Specifications (TS).
The proposed amendments would revise the acceptance criteria for TS 4.7.6.1.b.l.
This modification would change the allowable leakage past the auxiliary building safeguard air filtration system (ABSAFS) dampers M2A and H2B from none when tested at 30 inches water gauge to 5 cubic feet per minute (cfm) when tested at 1.5 times the system's design operating pressure.
The June 20, 1991, letter forwarded a summary of radiological analysis performed to determine an acceptable leakage limit in support of the proposed amendment.
The submittal dated October 8, 1991, contained an accident evaluation to demonstrate that with the new acceptance criteria for damper leakage, the doses from postulated accidents would remain within the NRC's acceptance criteria.
In the June 5,1992, letter the licensee clarified the proposed change to TS 4.7.6.1.b.1 to specify the test method and the test i
pressure.
These supplemental letters provided clarifications on the safety analysis and the surveillance requirements for the proposed TS that did not change the action noticed in the Federal Reaister on March 6,1991, and did not affect the initial proposed no significant hazards consideration determination, i
2.0 EVALUATION The ABSAFS at the Diablo Canyon Plant is designed to filter and adsorb any airborne radioactive material leaking from the emergency core cooling system (ECCS) equipment in the ECCS pump room areas following a design basis accident (DBA).
This system may also be utilized for filtering the containment purge following a LOCA.
The ABSAFS minimizes the potential impact of a radiological accident. The licensee took credit for this system in their analyses to demonstrate that the offsite doses and the doses to the control room operators were within the acceptance criteria of 10 CFR Part 100 and General Design Criteria (GDC) 19.
9304080290 930401 PDR ADOCK 05000280 P
. The ABSAFS has two supply fans which deliver filtered and preheated air to various locations within the auxiliary building.
Two exhaust fans take suction on the auxiliary building through a series of filters and discharge to the plant vent.
Because the exhaust fans have a greater capacity than the supply fans, this tends to maintain the auxiliary building at a slightly negative pressure.
Therefore, any building leakage tends to come from the outside into the building.
Dampers M2A and M2B are part of the safeguard exhaust duct portion of the ABSAFS. These dampers are open during the safeguards only mode and open during the building and safeguards ventilation mode when no safety injection (SI) signal is present.
In the open mode, the charcoal adsorbers, which are designed to adsorb elemental iodine and methyl iodide, are bypassed.
When a SI signal is present, the dampers are required to close so that the charcoal adsorbers are no longer bypassed.
Leak testing of these dampers ensures that potentially contaminated air resulting from leakage during an accident is not discharged to the environment without first being passed through a charcoal adsorber.
The current TS 4.7.6.1.b.1 for the ABSAFS for Diablo Canyon Units I and 2 requires a surveillance test to be performed on the M2A and the M2B dampers once per 18 months or after any structural maintenance on the HEPA filter or the charcoal adsorber housing or following painting fire or chemical release in any ventilation zone communicating with the system.
This surveillance requires verification that no detectable leakage occurs through these dampers when subjected to a bubble test at a pressure greater than or equal to 30 inches water gauge.
In the November 15, 1990, letter the licensee proposed that the surveillance requirement for the M2A and M2B dampers be performed on an 18-month basis and that the allowable leakage be increased from no detectable to 5 cfm.' The test pressure would be changed from 30 inches water gauge to 1.5 times the system design operating pressure.
After several discussions with the staff, the licensee modified the proposed change in the June 20, 1992, letter. The June 20, 1992, letter modified the surveillance requirement such that the test method, either a constant pressure or a pressure decay test, was specified as was the test protocol, ASME N510-1989. The proposed surveillance requirement would require the test to be conducted at the maximum operating pressure as defined by ASME N510-1989, which is 8 inches water gauge for the ABSAFS.
The staff has evaluated the licensee's submittal.
The staff has concluded that the change in the test frequency is appropriate because any structural maintenance on the HEPA filter or charcoal adsorber housings should not affect the ability of the dampers to maintain their integrity. The same rationale can be applied with respect to requiring a test following painting, fire, or chemical release in any ventilation zone communicating with the system.
Such releases should not affect the ability of the dampers to maintain integrity.
Obviously, the leakage characteristics would be required to be reestablished if work was performed on the dampers.
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. The staff has reviewed the licensee's proposed change in test procedure from the bubble test to the constant pressure or the pressure decay leak rate test.
The staff has determined that this change in test method is appropriate since the acceptance criterion has been changed to a quantifiable value.
The bubble test is not a test suitable for the quantification of leakage.
The test method, ASME N510-1989, is also acceptable since it provides the latest industry knowledge and experience on damper testing.
The licensee's October 8, 1991, submittal contained the licensee's calculations to demonstrate that even with dampers M2A and M2B at a flow rate of 5 cfm total, the doses were within the limits of 10 CFR Part 100 and GDC 19. The staff independently calculated the doses to the control room operator and to offsite individuals resulting from this additional leakage to determine if the licensee still met the acceptance criteria of 10 CFR Part 100 and GDC 19. As a result of these calculations, the staff has calculated the thyroid doses from all LOCA sources to be 12 rem to the control room operator, 93 rem at the Low Population Zone (LPZ) and 195 rem at the Exclusion Area Boundary (EAB), which are within the foregoing acceptance criteria.
Some of the assumptions utilized in the evaluation are included in the Table which follows.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the California State official was notified of the proposed issuance of the amendments. The State official had no comments.
4.0
[NVIRONMENTAL CONSIDERATION These amendments change a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements. The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.
The Commission has previously issued a proposed finding that the amendments involve no significant hazards considera-tion, and there has been no public comment on such finding (56 FR 9381).
Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
5.0 CONCLUSION
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i The Commission has concluded, based on the considerations discussed above, that (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Attachment:
l Table " Assumptions Utilized in the Determination of LOCA Doses" Principal Contributor: J. Hayes Date:
April 1, 1993 1
i
TABLE Assumptions Utilized in the Determination of LOCA Doses General LOCA 1.
Power level was 3580 Mwt.
2.
SRPs 6.4 and 15.6.5 for the evaluation.
3.
X/Q values for the EAB and LPZ were those presented in the original Diablo Canyon SER.
Values for the control room operator were based upon SRP 6.4 and took into account occupancy factors and the reduction credited for dual intakes with automatic selection capability.
4.
Filtration and adsorption credits for the ABSAFS and the control room system.
The credited removal efficiencies for the ABSAFS were 90% for elemental and particulate forms of radiciodine and 70% for organic forms.
Credited removal efficiencies were 95% for all forms of radiciodine for the control room system.
5.
In addition to the 5 cfm of bypass flow past dampers M2A and M2B of the ABSAFS, bypass flow was also assumed to include the 1% of system bypass associated with the inplace freon and DOP testing required by TS for both control room and ABSAFS.
6.
Unfiltered inleakage into the control room was 10 cfm.
7.
Containment purges occur at 672 and 696 hours0.00806 days <br />0.193 hours <br />0.00115 weeks <br />2.64828e-4 months <br /> after the LOCA and are 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> in duration for each purge. The purge flow rate was 300 cfm.
8.
Spray reduction factor was initially 10 hr for elemental forms of radiciodine and 0.45 hr for particulate forms. The elemental removal lasted until a DF of 200 was achieved. When a DF of 50 was achieved for particulates, the spray removal factor was reduced by a value of 10 for the remainder of the accident.
9.
The unsprayed region of the containment was to be 17%.
10.
Containment leak rate was 0.1% for the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of the accident and 0.05% for the remainder of the period of the accident.
11.
Control room operates with 2,100 cfm of pressurization flow being filtered and no recirculation flow filtered.
TABLE (Continued)
Assumptions Utilized in the Determination of LOCA Doses ECCS Leakaae Centribution 1.
Release due to ECCS operation is directly to the environment without credit for holdup and dilution associated with the auxiliary building.
2.
Filtration and adsorption credits taken for the ABSAFS.
3.
At the beginning of ECCS operation (0.395 hours0.00457 days <br />0.11 hours <br />6.531085e-4 weeks <br />1.502975e-4 months <br />), a 2 gpm leak occurs and continues for the remaining period of the accident. At 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after the LOCA, a 50 gpm leak occurs and lasts for 30 minutes.
4.
Of the ECCS flow which leaks,10% becomes airborne.
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