ML20236X623
| ML20236X623 | |
| Person / Time | |
|---|---|
| Site: | Portsmouth Gaseous Diffusion Plant |
| Issue date: | 07/31/1998 |
| From: | NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | |
| Shared Package | |
| ML20236X620 | List: |
| References | |
| NUDOCS 9808100147 | |
| Download: ML20236X623 (3) | |
Text
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. @ RECg 5
y 1- UNITED STATES g
j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20066 0001
\ *****/ July 31, 1998 DOCKET: 70-7002 CERTIFICATE HOLDER: United States Enrichment Corporation Portsmouth Gaseous Diffusion Plant Portsmouth, OH
SUBJECT:
COMPLIANCE EVALUATION REPORT: APPLICATION DATED l JULY 30,'1997, MINIMUM REQUIRED NUMBER OF AUTOCLAVE AREA SMOKE DETECTORS L
BACKGROUND By letter dated July 30,1997, the United States Enrichment Corporation (USEC) requested an amendment to the Certificate of Compliance for the Portsmouth Gaseous Diffusion Plant g (PORTS). The request is to clarify Technical Safety Requirement (TSR) 2.1.3.11 dealing with the minimum required number of operable smoke detector alarm circuits in the autoclave facilities; namely X-343, X-342A and X-344A. The amendment request was modified by USEC on May 29,1998, in response to a Nuclear Regulatory Commission (NRC) staff request for additional information (RAl) dated March 19,1998.
[ The Limiting Condition for Operation (LCO) for TSR 2.1.3.11 currently states:
l l Fifty percent of the installed Autoclave UF smoke detection heads in a facility shall be l operable.
USEC has proposed to revise this LCO to state:
Autoclave UF. smoke detection systems shall be operable.
! In addition to modifying the LCO, USEC has proposed to clarify TSR 2.1.3.11, Actions
- Statements, to normally require at least one operable smoke detector alarm circuit to cover an area above each autoclave in buildings X-342A (Feed Vaporization Facility) and X-344A (Toll Enrichment Services Facility) and each autoclave pair in building X-343 (Feed Vaporization and Sampling Facility). In response to the NRC staff RAI dated May 29,1998, USEC has also proposed to normally require at least four of the eight detector heads operable at all times in the X-343 facility. .This is to alleviate any potential adverse effects on timely detection of a release in the event of winds inside the building when one or both crane doors or hatches are open.
Changes were also made to Chapter 3, " Facility and Process Description," of the Safety Analysis Report (SAR). These changes involve the addition of new sections 3.2.1.1.6, "UF.
Leak Detection System," and 3.2.1.2.6, "UF Leak Detection System," and a new paragraph to section 3.2.1.3.6, "UF, Leakage Detectors." The new sections describe the operations and )
locations of the UF detection systems.
I 9808100147 980731 2 j PDR ADOCK 0700 C a. !
DISCUSSIO'N PORTS uses thirteen cylindrical (6,7, and 8 foot diameter) steam autoclaves in buildings X-343 (seven autoclaves), X-342A (two autoclaves) and X-344A (four autoclaves) to feed, transfer and sample UF. contained in large (2.5 ton to 14 ton) cylinders. These autoclaves were designed 4 and constructed in accordance with ASME Section Vill and provide safety by confining UF and l any reaction products in the event of a major UF release inside an autoclave. Steam used to l heat UF cylinders within autoclaves is typically controlled at approximately 5 psig. During the !
heating cycle, the UF. pressure inside a cylinder may be raised to as high as 100 psig. The pressure differential between the autoclave and the outside environment is maintained by way of a locking ring between the autoclave's hydraulically movable shell and fixed head. Containment valves are provided on lines entering and exiting the autoclaves to allow the autoclave to be '
placed in containment if there is a UF release inside a closed autoclave.
i Smoke detectors in the autoclave areas provide audible and visual alarms in the event of a UF. {
release. UF, (gas) reacts very vigorously with steam and water vapor. This hydrolysis reaction 1 generates HF (gas) and UO2F2 (solid). Since this reaction is exothermic and since pressurized UF, would be at high temperatures (130 F to 265 F), a released plume of UF. would generally tend to rise. Therefore, to effectively detect a UF. release in a timely manner, detector heads )
are placed above potential release points. Airborne UO2F2 can be observed as a light haze. l Gaseous HF is colorless and is not visible to the naked eye. However, when it is exposed to water vapor, it forms aqueous HF droplets (HF*2H2O (white smoke or fog)] which is readily observable. Therefore, a simple smoke detector can be used to detect a UF, release. HF also has an objectionable odor. As such, in addition to being visible, a UF release can also be readily detected by workers through smell. TSR 3.23 entitled, " Worker Protection from UF.
Process Hazards," requires workers to be trained in smoke detector alarm response procedures in the event of a release of UF ensuring compliance with the plant "see and flee" policy which requires workers to immediately evacuate upon observing a UF. release.
I The UF containment boundaries provided by the cylinder, pigtail, piping and valves inside and outside an autoclave out to and including the second containment valve, and steam and UF.
reaction product confinement bounc' aries provided by the autoclave shell and autoclave penetrating piping out to and including the second containment valve, are designated as "Q" systems. As such, USEC is required to apply the highest level of quality control (ASME NQA-1) to ensure that the pressure boundaries within these systems are maintained.
The autoclave facilitias are divided into areas or zones covered by separate alarm circuits. Most l circuits have two detectors. According to USEC operating personnel, these systems are very i reliable and hardly ever break down. These systems are required by TSR to be smoke tested at least semiannually. Activation of a single detector within a circuit activates an audible and visual j alarm at the control panel. The X-342A, X-344A and X-343 autoclave facilities, have three, two j and ten UF, detection zones / alarm circuits, respectively. The current TSR 2.1.3.11 LCO simply J l requires more than 50% of the installed detector heads in an autoclave facility to be operable. ]
Also, the specific numbers provided in the Actions Statement of the TSR for the autoclave facilities do not represent 50% in all cases. Furthermore, the current TSR does not specify which smoke detector heads need to be operable. Under the existing wording, inoperable smoke detector heads directly above an operating autoclave in X-342A'and X-344A and an o --
3 operating au'toclave pair in X-343 could satisfy the current LCO requirements without providing timely detection because of their potential remoteness to the autoclave.
USEC has proposed to clarify TSR 2.1.3.11 by deleting the LCO requirement of having more than 50% of the installed smoke detector heads to be operable for all autoclave operational modes to requiring at least one smoke detector alarm circuit covering an area above an autoclave to be operable for all operational modes. The staff has determined that these clarifications to the TSR addressing the Autoclave Smoke Detection System will avoid any confusion or misinterpretations of the TSR and, in fact, may enhance safety by providing more timely detection and alarm for a UF, release.
USEC has also clarified the TSRs by making reference to " smoke detector alarm circuits" instead of just " detectors," and removing the requirement for having a smoke watch or shutting down all autoclaves in the building if the minimum number of smoke detector alarm circuits are not operable. The Basis statement of the TSR has also been clarified to specify that only one smoke watch is required for the entire X-343 building which is consistent with the current TSR implementation practices.
l While reviewing USEC's certificate amendment request, the NRC staff raised a concern that l dealt with the fact that under windy conditions, buoyancy of plumes may be somewhat suppressed. Such conditions are much less credible in buildings X-342A and X-344A than in i X-343 which has large crane doors and hatches on the north and south ends of the building enclosure containing the seven autoclaves. Responding to the NRC staff concern, USEC proposed an additional condition for building X-343 which involves requiring at least four smoke detector alarm circuits to be operable in the entire building when any one of the seven autoclaves is not in Mode Vil; the shutdown mode. This is because both of the crane hatches and/or building side doors may be open to allow cylinder movement or for ventilation purposes on warm days. This situation, in conjunction with a brisk wind blowing in a predominantly northerly or southerly direction, could create wind conditions in the X-343 autoclave enchsure which may adversely affect the timely detection of a UF. release by smoke detector circuite directly above the autoclaves. The NRC staff has determined that the requirement for having et least four circuits operable in X-343 including one directly above the autoclave is adequate.
ENVIRONMENTAL REVIEW lssuance of the requested amendment to the Portsmouth Certificate of Compliance (GDP-2) to amend and clarify the number of smoke detectors required to be operable in an autoclave facility is subject to the categorical exclusion provided in 10 CFR 51.22(c)(19) and will not have a significant impact on the hur.ian environment. Therefore, in accordance with 10 CFR 51.22(b),
neither an environmental assessment nor an environmental impact statement is required for the proposed action.
CONCLUSION Taking into consideration the applicable safety requirements (administrative and installed hardware) for preventing UF releases associated with autoclaves, and past operational history at PORTS, the staff concludes that a major autoclave accidental release of UF. is highly
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unlikely. In addition, the staff concludes that the means for detection and mitigation of UF.
releases available at PORTS are reasonably adequate to provide for the protection of individuals I located onsite and offsite. Also, based on the information provided in the proposed TSR i 2.1.3.11 clarifying the number of smoke detectors required to be operable in an autoclave I facility, the staff recommends that the revised TSR be approved. In addition, the staff has concluded that the corresponding SAR changes are appropriate.
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The Region ill Inspection staff has no objection to this proposed action.
Princioal Contributor Yawar Faraz DISTRIBUTION: (Control No.190S)
Docket 70-7002 NRC File Center PUBLIC KO'Brien, Rill SPB r/f DHartland, Rill KWinsberg,0GC NMSS r/f NMSS dir. ofc. r/f
, FCSS r/fWTroskoski, FCOB PHiland, Rill CCox RCastaneira WSchwink, 1
FCOB OFC SPB 6 .hPBj h SPB, [ SPD [
NAME YFar Okadley fMartin M d [n DATE 7/ A /98 7/ 198 7/ 1 /98 7/ h /98 C = COVER E = COVER & ENCLOSURE N = NO COPY G:%MD11CER.POR OFFICIAL RECORD COPY