ML20211J665
| ML20211J665 | |
| Person / Time | |
|---|---|
| Site: | Humboldt Bay |
| Issue date: | 12/31/1998 |
| From: | PACIFIC GAS & ELECTRIC CO. |
| To: | |
| Shared Package | |
| ML20211J663 | List: |
| References | |
| NUDOCS 9909030222 | |
| Download: ML20211J665 (8) | |
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Attachm::nt PG&E Letter HBL-99-011 10 CFR 50.59 ANNUAL REPORT OF CHANGES, TESTS, AND EXPERIMENTS ,
JANUARY 1 THROUGH DECEMBER 31,1998 '
HUMBOLDT BAY POWER PLANT, UNIT 3 DOCKET NO. 50-133 1998 FACILITY CHANGES Listed below are the changes made to Humboldt Bay Power Plant, Unit 3 (HBPP) in 1998, along with brief descriptions of the changes and summaries of the safety evaluations. More complete records of these design changes have been reviewed by the HBPP Plant Staff Review Committee (PSRC), and the changes were determined not to involve an unreviewed safety question or a change to the HBPP Technical Specifications.
Description This design change package removed the two main exhaust fans, fan discharge
- ducting that was attached to a 250 foot ventilation exhaust stack, and plenum No. 2. It also installed a single exhaust fan, a High Efficiency Particulate Air (HEPA) filter unit and a 48" diameter stack which terminates 50 feet above ground elevation, including instrumentation and controls. The new instrumentation includes the stack gas sample system nozzle and a new stack flow primary element and transmitter.
Safety Evaluation Summary The difference between the new and the existing stack heights (250' vs. 50') with respect to the discharge air dispersion had the potential to increase the consequences of an accident previously evaluated in the Defueled Safety Analysis Report (DSAR). Nuclear Calculation No. N-238 demonstrated that in ca'.ra of a fuel handling accident with the new stack configuration, the dose to the maximally exposed individual at the site boundary does not exceed the 0.13 mrem previously evaluated in the DSAR. !
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During replacement and installation of the new exhaust system components, plant ventilation systems, supply and exhaust, were shut down. This resulted in !
loss of negative pressure in the refueling building, the preferred airflow direction, ND D R
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Attachm::nt PG&E Letter HBL-99-011 and also caused an overall rise in plant indoor ambient temperature. This temporary condition was acceptable because spent fuel was not allowed to be moved, and activities related to the modification were conducted outside the refueling building isolation boundary.
During removal of the existing ventilation. equipment and associated ducting, there was the potential for the release of airborne contamination to the environment through an unmonitored release path. To address the potential release, the internal surfaces were coated to fix any smearable contamination, prior to breaching the ventilation ducting.
- 2. Closure of the Settling Ponds (SE No.1998-06)
Description Paragraph 4.4.3.2 of the SDP states "The yard drain sump can be valved to the settling ponds..." These settling ponds have been closed and the yard drain
- sump discharge to the settling ponds was rerouted to the Unit 2 oily water sump. l I
Safety Evaluation Summary The modification to the yard drain system entailed re-routing the sump discharge, which initially went to the settling ponds, to Unit 2 oily water sump.
(The normal yard drain sump discharge to the inlet canal, and the discharge route to the turb!ne building drain system, were not modified.) The design function of the yard drain system has not been altered by this modification. The ;
Unit 2 oily water sump is designed to handle watt.' contaminated with oil, and can in an emergency be utilized to contain other liquids which are not suitable for off-site release. Thus the Unit 2 oily water sump is a functional equivalent to ,
the settling ponds, i This modification only affected piping which is not Unit 3 (nuclear unit) equipment. The abandoned piping to the settling ponds and the new piping to the Unit 2 oily water sump are outside of the radiological control area (RCA) and are not part of a Unit 3 aystem.
. Description This modification was to remove the existing 250-foot reinforced concrete Ventilation Stack down to approximately the 40' elevation, leaving the basement
Attachm :nt PG&E Letter HBL-99-011
' and the two existing, above-ground levels of equipment in place. The stack was replaced with a shorter. :mrbon steel stack, the installation of which is covered by Design Change P dage M-00429. The purpose of removing the stack was to reduce the seismic hazard to the stored spent fuel, plant personnel, and other structures within tho radius of the 250' stack.
Safety Evaluation Summary The crane, or a component of the crane, could fail, causing the load or the crane to fall, impacting one or more of the many potential targets. With crane reliability in standard application being very high (Iow probability of failure), it was our engineering judgment that with the additional administrative controls in place (increased safety margin, operational restrictions, and accident mitigation efforts), the effort to remove the stack did not increase the probability of an accident previously evaluated in the DSAR.
The north wall of the Liquid Radwaste Treatment Facility could fait due to the weight of the soil and the crane. This wall was analyzed for soil and crane loading. It was determined that the wall is able to withstand the surge loading from both the soil and crane and remain qualified under ACI 318. In addition to the analysis, monitors were installed on the accessible side of the wall in order to detect movement of the wall.
During the concrete cutting operation, radioactive contamination in the concrete dust could be released offsite. Engineering measures were taken to mitigate l dust and debris generated during stack removal. A water and slurry collection system was attached to the stack directly below the cutting area to collect the concrete slurry. The area of the cut was contained with respect to airborne contaminatian, and adequate engineering controls were employed to capture any contaminated debris generated during any stack removal activity that had the potential to generate airborne radioactive contamination. The cut line area i was sealed closed on the outside of the stack. As the diamond wire cutting saw broke through the interior of the stack, the dust and debris was collected in the plant ventilation system. The ventilation flow through the stack was reversed and material in the stack was pulled down through the stack , into the newly installed HEPA filtration system, and discharged through a monitored pathway.
Monitoring for airborne radioactive contamination was performed during cutting and removal operations.
1998 PROCEDURE CHANGES Listed below are the changes made to procedures or new procedures in 1998 as described in the SDP, along with a brief description of the changes and a summary of the safety evaluations. More complete records of these procedure changes have been
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PG&E Letter HBL-99-011 l reviewed by the PSRC, and the changes were determined not to involve an unreviewed safety question or require a change to the HBPP Technical Specifications. l
- 1. ED&Ol E-3 The Liquid Radwaste System Discharge Requirements (SE No.1998-01)
Description .
HBPP Technical Specifications previously required all radwaste discharges to 1 be filtered. However, HBPP Technical Specifications were revised (Amendment I 32 to the license) and most of the Operating Limits for the Radwaste System were transferred from the Technical Specifications to the SAFSTOR Offsite Dose Calculation Manual (ODCM). During this transfer of information, the radwaste discharge filtering requirement was changed to require filtering radwaste discharges only if projected monthly doses from the discharge will exceed the action levels stated in ODCM Specification 2.5. As a result, ED&Ol E-3, Step 6.1, was revised to reflect the ODCM requirement.
Safety Evaluation Summary This revision of procedure ED&OI E-3 was made to be consistent with Revision 1 of the ODCM, is administrative in nature, and therefore did not result in any {
safety evaluation issues. i 1
- 2. ODCM SAFSTOR Offsite Dose Calculation Manual (SE No.1998-02)
Description The SAFSTOR Offsite Dose Calculation Manual (ODCM) was revised to reflect the revised Technical Specifications (Amendment 32 to the license). The ODCM revision identified the need to update the SAFSTOR Decommissioning Plan (SDP) to make the two documents consistent. The purpose of this evaluation was to clarify the expectations in SDP Section 5.2.2. "Onsite Environmental Monitoring."
SDP Section 5.2.2. contains the following three areas of discussion for onsite environmental monitoring:
- 1) the four environmental monitoring activities, which include groundwater monitoring wells, stack radiation monitor, continuous sampier in the i discharge canal, and fence line dosimetry stations,
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Attachment PG&E Letter HBL-99-011
' 2) annual repods will include average and maximum values for total gamma, beta, alpha activity, and concentrations of indicator nuclides, and
- 3) routine surveys of the rad waste treatment buildings.
The question was, do all the specific analyses described in discussion item 2) above apply to all four monitored activities listed in discussion item 1) above.
The specific analyses described in discussion item 2) do not apply to all the monitored activities listed in discussion item 1) above. For example, the stack radiation monitor and fence line dosimetry stations do not identify alpha activity or concentrations of indicator nuclides. The contents of annual reports referenced in the discussion item 2) all relate to onsite environmental monitoring, but address different aspects of the program. However, in reading this section of the SDP it was not clear that the discussion of the four environmental monitoring activities and the annual reporting requirements are separate issues. The statement regarding requirements for the annual report was misleading and required the SDP to be clarified.
Safety Evaluation Summary
. The revision to the ODCM and the subsequent update of the SDP were administrative in nature because information was clarified regarding annual repoding requirements. This safety evaluation provided justification for updating SDP, Section 5.2.2 regarding requirements for the annual report to state " Annual reports will be submitted in accordance with Technical Specifications requirements." This results in a commitment to comply with all regulatory requirements while allowing for the details of such annual reports to be specified in the appropriate document such as the ODCM.
- 3. ODCM SAFSTOR Offsite Dose Calculation Manual (SE No.1998-03)
Description The SAFSTOR Offsite Dose Calculation Manual (ODCM) was revised to reflect the revised Technical Specifications (Amendment 32 to the license). The revised Technical Specifications, Vll.F " Radioactive Effluents Control Program,"
item 2, provides for liquid effluent releases up to a level ten times the effluent concentration limits of 10 CFR 20, Appendix B, Table 2, column 2. The SDP was updated to also reflect the revised Technical Specification information.
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Attachment PG&E Letter HBL-99-011
' Safety Evaluation Summary The ODCM revision and the subsequent update to SDP, Section 4.4.3.1,
" Process Radiation Monitoring System," were administrative in nature and did not result in any unresolved safety evaluation issues because information was modified to reflect the latest version of the Technical Specifications. This latest information allows discharge of liquid effluents up to a level of ten times the 10 CFR 20, Appendix B, Table 2, column 2 limits (Specification Vll.F.2).
- 4. SAFSTOR DECOMMISSIONING PLAN, Section 4.4.5.
(SE No.1998-04)
Description The SAFSTOR Decommissioning Plan, Section 4.4.5, " Radioactive Waste ,
Processing and Disposal," was revised to describe expected future liquid and I solid waste processing and disposal procedures at HBPP. Technological developments in processing and the availability of off-site waste processors are significant factors that influence decisions on waste handling since the j SAFSTOR Decommissioning Plan was written. Additionally, editorial changes were made to clarify practices.
Safety Evaluation Summary The use of secondary processors for off-site solid waste processing and the allowance for additional methods and greater flexibility in solid waste packaging did not affect any of the present accident analyses nor create any new accidents that could be credible during SAFSTOR. These changes did not reduce the protection of the health and safety of the public, and did not increase the occupational dose received by those radiation workers that perform the processing and the packaging of solid radioactive waste. As a result, there are no potential safety evaluations issues for these changes.
- 5. HBAP A-2 Plant Staff Review Committee (PSRC)
(SE No.1998-07)
Description This procedure change also revised the SDP, Section 4.2.1 regarding responsibilities of the Senior Vice President and General Manager, the Vice President, Nuclear Technical Services (NTS), and the Plant Manager. These changes provided an updated description of the responsibilities of the SVP&GM to be consistent with the Technical Specifications, indicated that the VP-NTS is
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Attachm::nt PG&E Letter HBL-99-011
' responsible for_ the oversight of HBPP nuclear activities, and that the Plant-Manager ilBPP reports to the VP-NTS.
Safety Evaluation Summary
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The revision to SDP, Section 4.2.1 " Decommissioning Project Team" to identify current reporting relationships was administrative and does not result in any ,
unresolved safety evaluation issues.
Description This procedure provided instructions for the proper erection and operation of the Aliclimber. The Aliclimber platforms provided access to the stack for cutting the
- sections and rigging the sections for removal. The platforms contained handrails and interconnecting flooring to allow the Aliclimber to surround the circumference of the stack.
Safety Evaluation Summary
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The working platform attached to the stack could fall through the roof of the Refueling Building, crushing the fuel in the pool and releasing some or all of the Kr-85 inventory in the fuel. The hole in the roof would provide a different pathway for the dispersion of the gaseous effluent than the normal plant exhaust. The two Aliclimber Mast Climbing work platforms and masts are ;
engineered devices provided by Klimer Platforms, Inc. and are specifically l designed for this type of service. They were installed by. qualified Klimer j Platforms, Inc. personnel using manufacturer's procedures. The masts were attached to the stack with anchor bolts and tie-ins per the manufacturer's installation procedure.' The platforms, the ground bearing loads and the anchor points were independently evaluated by P.G.&E civil engineer personnel to assure adequate holding strength and that they would not result in degradation to the stack which could result in the platform slipping, or pulling away from the stack and impacting the Refueling Building. )
The additional weight of the work platform near the top of the stack created additional static loading on the stack and change the response of the stack to seismic and wind loads. This had the potentia! to cause the stack to fail and a portion of the stack fall through the roof of the Refueling Building, crushing the j fuel in the pool and releasing some or all of the Kr-85 inventory in the fuel.
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Attachmsnt PG&E Letter HBL-99-011
' The stack's structural stability was reviewed to assure that the addition of the work platforms and masts did not turn the stack into an unstable structure. The additional loads from either wind or a small seismic event had a negligible effect on the structural stability of the stack.
- 7. L-3 Defueled Safety Analysis Report (SE No.1998-10)
Description The Defueled Safety Analysis Report (DSAR), previously called the SAFSTOR Decommissioning Plan (SDP), was revised as required by the 1996 NRC !
decommissioning rule, specifically 10CFR50.71 The name of the report l changed from SAFSTOR Decommissioning Plan to DSAR. The revision includes five types of changes that: (1) provide editorial or typographical corrections, (2) provide clarification of information, (3) satisfy new regulatory l requirements, (4) reflect changes in previous safety evaluations (reviewed by PSRC) that were made since the last revision of the DSAR, and (5) delete identification of specific types of instrumentation.
Safety Evaluation Summary None of the DSAR changes had an affect on equipment functions or operating parameters, and did not modify plant configuration, organization, activities or operations, unless evaluated by a previous safety evaluation.
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